|AGA Europa 51||AGA 1771||Blaupunkt Granada 2525||Blaupunkt Granada 2626||Centrum GU60||Centrum W51||Centrum 261||Concerton V488|
|Concerton U584||Dux V136||Dux V373||Dux V1370||Graetz Melodia 519||Graetz Sinfonia 422||Grundig K41S||Grundig 97S|
|Grundig 3097S||Grundig 5080S||Ilse Gracia 2338||Kungs 755UKV||Luxor Ambassadör||Luxor Diplomat||Luxor Luxorita 555W||Luxor Populär 493W|
|Luxor Populär 3095W||Luxor Tapto||Luxor Tenor||Loewe-Opta Truxa||Marconiphone 853||Orion 99||Philips B2X63U||Philips BS371A|
|Philips BS596A||Philips BX760X||Philips BX998A||Philips H4S03A||Philips 522A||Philips 796A||Philips 915X||Philips 933A|
|Philips 940A||Philips 990X||Radiola 475V||Siemens M57||Telefunken 875GWK||Telefunken Opus 6||Telefunken Opus 9||Tjerneld Super 7|
I don´t collect them with a certain strategy. The radios find their place here by coincidence because I can´t help taking care of the worn, non-working sets and give them new life and a good home. The fun part is troubleshooting and tuning-up as well as finding the parts needed in my junkbox. The restored radios which have no given place in my rooms are presently piled in the wardrobe or the garage.
Antique radios don't appeal to me as much as those from the 1950´s. People who fancy old things often have an emotional relation to them, perhaps as memories of their childhood. Magic eye, gold-gleaming speaker cloth, lots of geographical names on the well-lit dial glass, brass edgings, white pushbuttons, everything enclosed with polished hardwood, it was that kind of radio that I had a yearning for when I was a boy. The manufacturers´ brochures boasted with the number of tubes, the more the better of course. As I had started with dx-ing I preferred radios with more than one shortwave band and on the 80 m band were AM-transmissions from Swedish radio amateurs. In spite of all this my first radio turned out to be an old set.
A Marconiphone 853 alias H.M.V. 657 from 1938 was bought at an auction for 5 kr (my weekly pocket money) in the late fifties. It has LW-, MW- and two SW-bands (13-30 and 30-90 m), tuned RF-stage, magic eye and motor-driven tuning capacitor with buttons for eight preset favourite stations on LW and MW. A circular logging scale facilitates tuning and it is driven together with the dial rod by a thin wire so there is no need to change a cord. The band indicator is driven by a chain from the switch. The dial.
The tubes are Marconi´s equivalents to American octal tubes: KTW63, X65, KTW63, DH63, KT63, Y63, U50. KTW63 have fixed screen voltage although they are beam tubes, the limited dynamic range of the magic eye required a low AGC-voltage. The electrodynamic loudspeaker is big with 62 Hz resonance frequency, but there is no negative feedback in the power amplifier. Output power is 2 W at the onset of clipping and the frequency response of the AF-amplifier is 40 Hz-6.5 kHz at -3 dB. This was a great receiver for its time, but a design mistake is that the oscillator tuned circuit is on the grid side rather than on the plate side which detoriates frequency stability on shortwave. However, this was done on recommendation from the tube manufacturer. The price in England was 39 guineas and in Sweden 460 kr.
I have replaced electrolytic and paper capacitors, five tubes are original ones but the magic eye is now UM4. As mixer tube 6J8G will work but not ECH35. Because I don't care for museum condition but want to use my sets, I have put a PCIM177 frequency readout behind the glass, zener-stabilized the voltage to the oscillator and replaced the tone control capacitor with an antenna switch. I can on the SW-bands select either the original high-impedance antenna connector (10 pF capacitive coupling to the control grid) or a low impedance connector coupled to a broadband transformer 1:9. The sensitivity varies between 3-9 µV. An S-meter has been placed behind the glass to the left of the magic eye (not visible on the photo).
In the beginning of the 1960´s I mostly listened to the pirate station Radio Nord with it, but later in the 1980´s I used the radio for renewed dx-ing during a couple of years. It was then I added the digital display which for the first time let me know where I was listening. The latest improvement is addition of a detector for SSB/CW, for a steady tone it became necessary to replace the mixer´s AGC with a fixed negative voltage when the detector is in use.
When I started with amateur radio it was with telegraphy and I needed a beat oscillator. As such I borrowed the family radio which besides LW, MW and UKV also had two SW-bands, 16-55 and 55-180 m, and whose tuning could be chosen so that the local oscillator interfered with the Marconi set to give the necessary beat note. This Swedish Kungsradio 755 UKV from Göteborg, of 1955 vintage, became my gateway to the dx-hobby. It was in daily use until the year of 2002 and still works reliably after changing of tubes, capacitors and dial lamps. I have replaced the selenium rectifier with silicon diodes, added a mains voltage fuse, separated the connected screen grids of the mixer and IF-tubes and added trimming capacitors to the SW antenna circuits.
The tubes are ECC85, ECH81, EF85, EABC80, EL84, EM34. Sensitivity is 4-8 µV on the SW-bands which are most suited for a low impedance antenna. There is no ferrite antenna and the tone control is a simple treble suppressor. The loudspeaker (Philips 9768 with 68 Hz resonance frequency) is half-hidden behind the dial glass, but in spite of that the audio quality is good. The internal loudspeaker can be switched off when an external one is used. The frequency-independant negative feedback is supplied to the cathode of the power tube, with my increased plate voltage the output power is 2.6 W at the onset of clipping and the frequency range is 36 Hz-28 kHz at -3 dB, so I have doubled the value of the limiting capacitor connected to the plate of the AF preamplifier. The rotary band switch was out of fashion when this set was made, most radios had pushbuttons. The price on sale was 300 kr, reduced because the radio was old stock. The dial.
A Swedish Luxor Tenor 4192W from 1962 was found at a flea market for 75 kr, the original price was 335 kr. Three tubes, three capacitors a dial lamp and a fuse had to be replaced and the selenium rectifier had so high voltage drop that I put silicon diodes in parallel with it. The SW-band covers 6-18 MHz and the FM-band 87-101 MHz. The single tone control affects both bass and treble. There is a ferrite antenna for MW and LW, for SW a piece of wire inside the cabinet is attached to the high impedance circuit. Sensitivity on SW is 10-20 µV and the antenna coupling coil impedance is 8 µV in one radio and 13 µH in another one.
The tubes are ECC85, ECH81, EBF89, ECC82, EL84, EM84. Notice the symbol for LUFOR (air defence warning) on LW, characteristic of the time, where the Swedes were supposed to listen for important messages in times of stress and calamity. The dial has channel numbers on MW and LW, which I have seen only on Swedish Luxor and Radiola radios.
Another Tenor-chassis is installed in a home-made cabinet measuring 37x17 cm because the original cabinet was found broken in the 1960´s and the rear cover was missing. I use a separate speaker with it, giving better sound quality than what the built-in oval loudspeaker with 165 Hz resonance frequency can produce. I raised the output power from 1.9 W to 2.8 W and filtered the plate current with an extra choke in this radio.
Luxor Tapto 4194W from 1962 has the same chassis as the Tenor above but the loudspeaker is bigger, 7" x 5" with resonance frequency 130 Hz. One tube, three paper capacitors and a dial lamp had been changed and the selenium rectifier is replaced with a silicon diode bridge. The FM tuning capacitor was stuck and needed lubrication. It is unusual that the volume control lacks loudness compensation, the output power is 1.9 W at the onset of clipping and the tone control gives the following results all related to 1 kHz: End position with max. bass +13 dB at 60 Hz and +6 dB at 10 kHz, end position with min. bass -12 dB at 66 Hz and +12 dB at 7.4 kHz, midrange +8 dB at 60 Hz, +13 dB at 7 kHz and +6 dB at 17 kHz. The same radio was sold as Skantic Vokalist and cost 365 kr. This radio was a gift.
This Swedish Luxor Populär 3095W, made in 1956 in Motala with original price 427 kr, was found at a flea market for 75 kr. It has LW, MW, SW and the FM-band extends to 108 MHz, laudable forethought or just a cut-price on Telefunken´s converters for the USA market. The tone control is a four-position switch: one for less bass, one for the full register (44 Hz-4000 Hz at -3 dB och 28 Hz-5500 Hz at -6 dB), one for slight and one for heavy attenuation of high tones. By removing a capacitor between the anode and control grid of the EL84 I raised the treble limit to 8 kHz at -3 dB and 13 kHz at -6 dB and I chose a smaller capacitor for the strongest attenuation. There is no loudness compensation in the volume control. The radio has two loudspeakers, a 6-inch one with 4 ohm and 90 Hz resonance frequency and an electrostatic tweeter that is too weak to be heard. The output power is 2.2 W at the onset of clipping.
The tubes are ECC85, ECH81, EF85, EABC80, EL84, EM80, EZ80. The ferrite rod which works on MW only is adjustable from the rear. A short piece of wire inside the cabinet works on LW and SW. The SW-band 19-52 m has fine adjustment by means of the UKV-knob with the cursor initially placed on 97 MHz. I replaced four tubes and the paper capacitors, added a mains fuse, lowered the heater voltage with 0,17 ohm 3 W and increased the value of the filter electrolytic capacitor. I use greater decoupling capacitors in the IF-stage, I consider 2.5 nF too little, and I got more amplification on the AM-bands. The sensitivity is about 6 µV on LW and MW, on SW where the input is intended for high impedance antenna my measurement showed 13-35 µV. The inductance of the antenna coupling coil is 8,2 µH on SW, 210 µH on MW and 7 mH on LW. White letter and numbers had fallen like autumn leaves for the indicating rod so I sprayed clear lacquer on the glass to keep the remaining ones fixed.
Luxor Luxorita 555W from 1953 belongs to the smallest mains-operated radios, something for one who needed a set in the kitchen or the summer cottage. Yet it has two SW-bands, 17-51 m and 75-200 m, so it received both amateurs and fishing boats. It is a variant of a model which had been available since the late 1940´s. On the back there is a sliding switch for treble cut which is not necessary, the 6-inch speaker gives a balanced sound although without deep bass and the output power is just over one watt. There is no switch position for record player, one has to disconnect the antenna. I have not measured the sensitivity but it appears to be equal to that of bigger radios. The inductance of the antenna coupling coil is 8 µH on SW1, 87 µH on SW2, 1.2 mH on MW and 7.8 mH on LW.
The tubes are 6BE6, 6BA6, 6AV6, 6AQ5, 6X4, all Swedish-made SER-tubes. The rectifier is a halfwave circuit, unusual in an AC set but it probably saved some money on the transformer. I changed to a bridge rectifier by adding two silicon diodes and got higher voltage with less hum. The radio seems to be little used, I replaced a tube, a resistor, an electrolytic capacitor and I added a mains fuse. The transformer has seen some damage so I must use the 250 V winding. Therefore I have added a small 18 V-transformer inside to give the radio correct voltage. I also added rubber strips between cabinet and chassis to get rid of microphonics. The radio was a gift.
Luxor Populär 493W from 1951 has basically the same circuit as the 555W above. The tubes are 6BE6, 6BA6, 6AV6, 6V6GT, 6X4. Differences are the power tube, a tone control at the front, a knob for fine tuning on the shortwave bands (moving metal plate near the oscillator coils) and a separate switch position for gramophone. The sensitivity is given as 10 µV in the service document. "Built-in antenna" means about 40 cm metal foil attached to the antenna terminal. There was a halfwave rectifier which I changed into a fullwave one, the same improvement as in the 555W above. All tubes were the original ones when I got the radio as a gift, I changed three of them as well as the dial lamp. The 6-inch speaker has 100 Hz resonance frequency, the previous owner had put a switch on the rear to cut it off and I guess that a separate loudspeaker cabinet gave better sound.
Philips B2X63U "Philetta" made in the Netherlands in 1956 became very popular as supplementary radio after the introduction of a second radio channel on the UKV-band because it was cheap and needed little space and there was often a bigger radio in the household. With improved housing conditions it also found its way into the teenage room. It is an AC/DC-set, both because there were many places with DC-mains even in the 1960´s and a transformer would make the radio bigger and more expensive. In spite of its compact size 19x17 cm the reception capability is as good as that of bigger radios, there are just as many tubes and circuits and the audio power (1.5 W at the onset of clipping) is enough, but everything is compressed and the components are placed in layers below the chassis. The few capacitors that need to be replaced are easily reached, however. The cabinet is made of plastic and on the front there is a plastic piece with dial and vertical ribbons in front of the loudspeaker net. It is lighted from beneath by two lamps and it gives the radio a pleasant appearance in a dark room. For MW and LW there is a built-in ferrite rod but for UKV an external antenna is required. Even a SW-band is included but limited to 23-51 m and it has no other markings than the four broadcast segments. There are separate knobs for UKV- and AM-bands and behind the loudness type of volume control there is a treble-cutting tone control.
The tubes are UCC85, UCH81, UF89, UABC80, UL84, UY85. I replaced the mixer tube and four capacitors, put in a new temperature fuse and increased the value of the run down filter capacitor with 33 uF in parallel. The SW-band needed a change of two capacitors in the antenna circuit for full sensitivity and after that it measures 4 µV for 50 mW output power at 10 MHz. With regard to input power to the UL84 the AF output should be twice as high, the low efficiency probably depends on a compromise in impedance matching to make the radio usable with 127 V mains, but with connection to external loudspeaker the sound is rich enough. I did not expect this sort of radio to end up in my collection but it is better than I had anticipated and it was free in the scrap container.
Found at a scrap-yard was this Swedish Centrum 261 from 1958, it was made by Gylling & Co in Stockholm and the original price was 495 kr. Besides LW, MW and UKV it has two SW-bands, 18-50 and 55-185 m. The UKV-knob gives bandspread on the high frequency SW-band. The radio has "3D-sound" using three loudspeakers, an oval 4 ohm Isophon P1521, 19x13 cm with 100 Hz resonance frequency, and on each side a 5 cm Voxtone tweeter (18 ohm and 1 kHz resonance frequency) which can be switched off with one button and the red button turns off all three, a useful gadget for anyone using a magnetic loop for hearing aid or had an external loudspeaker cabinet. Such is recommended because bass reproduction of the main speaker is not good enough and worse than that of Granada or Truxa below. The tone control attenuates treble with 4 dB while four small buttons select fixed registers, Orchestra-Opera-Solo-Jazz. The power output is 2.2 W at the onset of clipping.
The register buttons were a whim of fashion, separate controls for bass and treble would be more useful. Without any pressed button the sound is suitable for speech with +3 dB at 3 kHz, -3 dB at 560 Hz and -6 dB at 300 Hz. Solo has the same treble response, 9 kHz at -3 dB and 11 kHz at -6 dB, but reproduces more of the medium range. Jazz enhances high tones, Orkester have the same treble response but gives more bass with 120 Hz at -3 dB and 65 Hz at -6 dB. Opera lies something between them at frequencies below 1 kHz. All figures relate to 1 kHz.
The tubes are ECC85, ECH81, EF89, EABC80, EL84, EM84. The radio lacks a ferrite antenna for LW and MW but can use a UKV-antenna for the AM-bands. The sensitivity is 6-12 µV on SW. The inductance of the antenna coupling coil is 0.7 µH on SW2, 3 µH on SW1, 12.8 mH on MW and 24 mH on LW. I have changed electrolytic and paper capacitors, dial lamps and three of the tubes and I inserted a mains fuse. The selenium rectifier is replaced with silicon diodes and a 9 kHz trap across the output transformer is removed because its frequency had decreased to 8 kHz. The chassis has holes punched for a second IF-stage, an ambitious technician who finds suitable IF-transformers can improve the sensitivity. On the back is a connector for external volume control using screened cables. It is unusual to find names of Swedish stations on an FM-band dial but here they are.
I couldn´t help buying this Blaupunkt Granada 2626 from 1960 at the flea market for 200 kr. It worked from the beginning and the tubes are in working condition, but I replaced the paper capacitors and use silicon diodes instead of the selenium rectifier to be on the safe side. The tubes are ECC85, ECH81, EF89, EABC80, EL84, EM84. There are two SW-bands, 17-50 and 60-180 m, and the UKV-knob gives bandspread on the high frequency SW-band. News from this year is the use of a printed circuit board but its solder side is unfortunately partly unaccessible. The sensitivity on the AM-bands is 10 µV. The register buttons HiFi, Solo and Sonor work beside the separate controls for bass and treble. The main speaker, 6 ohm and resonance frequency 80 Hz, is on the front and two smaller ones with resonance frequency 1100 Hz are on the sides. It is similar to the Centrum above but has better sound, built-in ferrite antenna for LW and MW adjustable from the rear, and the built-in UKV-dipole works on SW. The original price was 565 kr, typical for a German medrium-priced radio of good quality.
Blaupunkt Granada 2525 from 1959 has only one shortwave band, apart from that the circuit is almost the same as that of the 2626 above even if the chassis is of older design without printed circuit board. The Sonor button has no electric function, it just brings back the other two register buttons. The radio needed five new tubes, replacement of all paper capacitors, an electrolytic capacitor and I replaced the selenium rectifier with silicon diodes. This radio was a gift.
Grundig 3097S from 1958 is similar to the Blaupunkts above. The tubes are ECC85, ECH81, EF89, EABC80, EL84, EM34. The original price was 565 kr but my winning auction bid was 2 kr. The radio has an oval speaker, 3 ohm and resonance frequeny 90 Hz, on the front and a 4 ohm oval loudspeaker with resonance frequency 500 Hz on each side. Output power is 2.6 W at the onset of clipping. The tone control comprises four knobs, the outer ones are conventional bass and treble controls while those in the middle activate traps on 1.5 and 3 kHz if the broad button in the middle is pressed. In addition to them is pushbutton for Speech which reduces bass, the Music button without electrical function just brings back the other buttons so it can be used to turn off the magic eye. The volume control has a loudness characteristic, I always measure the frequency response at full clockwise position but in this model the -3 dB limit is then just 3 kHz, with 2/3 position the upper limit is 12 kHz or more. The bass response is good down to 40 Hz.
A fixed ferrite rod, switchable from the front, works mainly on MW since on LW it is just a fraction of the total inductance. I replaced four tubes including the magic eye which is now UM4 with voltage doubler to the heater, all paper capacitors and two small electrolytic capacitors. On SW there were no trimming capacitors in the tuned circuits so I installed two instead of the fixed ones and that improved both calibration and sensitivity (8 µV). This well-sounding radio is in mint conditionand another set which is a gift sits on the spare shelf.
Grundig 97S from 1959, original price 335 kr, I couldn't resist such a cute little radio in mint condition for the bedside table so I paid 150 kr for it. The brown plastic case forms a nice contrast to the bright front with its white knobs and pushbuttons. There are separate knobs for AM-FM, ferrite antenna, LW-MW-SW, treble-reducing tone control and buttons for Music or Speech. The tubes are ECC85, ECH81, EF89, EABC80, EL84, EM84.
I had to replace three tubes, a resistor, all "ERO 100" paper capacitors, change the oversized mains fuse and lubricate the UKV tuning capacitor which was stuck. Moreover I replaced the selenium rectifier with a silicon bridge which raised the plate voltage with 50 V. The oval loudspeaker, 6" x 4" with 125 Hz resonance frequency, has 2.2 ohm impedance. Output power is 2 W and the audio bandwidth 77 Hz-8500 Hz at -3dB and 52 Hz-10500 Hz at -6 dB. The sound is good enough in spite of the small cabinet and with a short antenna wire along the cornice the radio receives SW-stations well with careful treatment of the tuning knob, but the sensitivity on the lower frequency half of the band is lower than I had expected.
Grundig 5080S from 1956-57 is a premium model of tabletop radio which I found in a second-hand shop for 200 kr, a big-sized cabinet 68 cm wide and 43 cm high. The original price was 795 kr. It has a five-stage tone control, "Wunschklang-Register", a push-pull amplifier with 8 W power at the onset of clipping and five loudspeakers of which two are electrostatic tweeters. Two knobs are conventional bass and treble controls while those in the middle activate traps on 750, 1800 and 4000 Hz. With the controls adjusted for a flat response the -3 dB limits are 50 Hz and 7 kHz but they are extended to 35 Hz and 13 kHz respectively if one reduces the intermediate frequencies. The 4000 Hz control also affects two IF-transformers for variable bandwidth 4-12 kHz in the two IF-stages.
The tubes are ECC85, ECH81, EF89, EF80, EAA91, ECC81, EBC41, EL84, EL84, EM34. A ferrite antenna for MW can be rotated from the front with a position indicator and external antenna is switched in with a push-button. The ferrite rod only works partly on LW where it is in series with the main inductance. The sensitivity on SW is 6 µV for 50 mW output measured with a 200 ohm signal source. The front speaker measures 28x16 cm with 6 ohm impedance and 75 Hz resonance frequency, on the sides are 22x14 cm with 4 ohm impedance and resonance frequency 80 Hz and 95 Hz respectively. The different resonances are chosen deliberately and the reason for not using small tweeters on the sides is that all three are needed to cope with the output power, they are wired in series to offer 14 ohm impedance. The connector for external 5 ohm speaker is attached to a tap on the output transformer. Vibration resonancies were removed by tightening the screws and nuts on the baffles.
All tubes except EAA91 and EM34 are replaced as well as the dial lamps, the magic eye has got better brightness with its plate voltage raised with 70 V, a temporary solution due to lack of a new tube. The paper capacitors (ERO and KS) are replaced and silicon diodes are used instead of the selenium rectifier, the mains fuse is changed to the correct rating and the heater voltage is lowered with a 0.1 ohm 5 W resistor. All moving parts were lubricated to make the radio work and the UKV-tuning mechanism needed some metal washers inserted for increased spring tension. The electrostatic tweeters were out of order, they consist of a plastic sheet with its outer side copper-plated and its inner side pressed against an earthed metal grid. The copper side has 230 V DC on it together with the AC voltage. I made one tweeter work after cleaning oxide from the connecting piece of metal pressed against the copper sheet. The other tweeter is replaced with a conventional 4 ohm one wired through a 4.7 µF capacitor in series with 3.3 ohm..
The sound is impressive with deep bass which makes playing of gramophone records with a crystal pickup enjoyable. There are also connections for tape recorder with a separate pushbutton for it and for Grundig´s HiFi-cabinet which I doubt was sold in Sweden.
An unusual piece of furniture from 1961 comes from the German furniture factory Ilse which also included radio chassis from German plants in what looks like 19th century style. This model Gracia 2338 holds a Telefunken chassis 2180 and behind the upper door was a Telefunken TW504 record changer. The tubes are ECC85, ECH81, EBF89, ECC83, EBC91, EL84, ECL86, EM84. The radio has a ferrite antenna, separate controls for bass and treble and pushbuttons for Bass-Solo-Intim-Jazz which reduce or enhance low and high frequencies. There is a 26x18 cm full-range loudspeaker with 80 Hz resonance frequency on the front and two 10 cm ones on the sides for midrange and treble. The UKV tuning knob gives bandspread on the SW-band which covers 5.9-18 MHz.
The word "Stereo" only applies to the record player if it has a stereo pickup, not the radio. Strangely enough the left channel goes only to an amplifier for medium and high frequencies to one loudspeaker on the side while the right channel goes to both the other side speaker and the front speaker where the full-range amplifier handles the bass tones from both channels. The radio needed change of "ERO100"-capacitors and slight tuning-up and I increased the audio power because I felt that the tube currents left some margin. Silicon diodes have replaced te selenium rectifier. The tone arm of the record changer was broken so I replaced the changer deck with a tape cassette deck. With both doors closed nothing reveals the technique behind them and the sound is great after I removed weak 100 Hz-hum with extra filtering of the plate current. The price in Germany was 998 DM.
A friend who knows better than throwing radios in the trash bin left this Swedish Dux V373 from 1956-57 to me. Its original price was 499 kr, it was made at the Philips plant in Norrköping and exists in the Philips-version as BS461A. It has had rough usage but after I changed the tubes and many capacitors it works well. The radio has separate bass and treble controls as well as variable AM-bandwidth. There is no ferrite antenna but a built-in frame antenna for MW-LW. The two SW-bands cover 1.6-4.8 MHz and 5.9-16 MHz and offer the high sensitivity of 4 µV. The UKV-band covers 87.5-100 MHz with good sensitivity due to two IF-stages. The tubes are ECC85, ECH81, EBF80, EF89, EABC80, EL84, EM80, EZ80. This worn set with two loudspeakers on the front, 7-inch in parallel with 6-inch, is my garage radio.
This Swedish Philips BS371A from 1957-58 is a cheaper sibling to the Dux above from the same plant, the original price was 430 kr. They have much in common. The differences are a single IF-tube, just one SW-band and one knob for tone control and fixed AM-bandwidth. Common features are two loudspeakers, 7-inch and 5-inch and a frame antenna. The tubes are ECC85, ECH81, EF89, EABC80, EL84, EM80. I changed tubes, made the set play with contact spray and and put silicon diodes across the selenium rectifier to raise the plate voltage. The magic eye is replaced with an UM80 whose heater is fed with 18 V from a voltage tripler. This radio was a gift for spare parts but since it was easy to restore it will stay in working order on my bookshelf. The same chassis is used in Dux V372.
Dux V1370 from 1956-57 is a Swedish tabletop radiogram which also came from the Norrköping plant and cost 645 kr. It has two IF-stages but the second one only for FM. The AF-amplifier consists of a transformerless single-ended push-pull stage which feeds two 5-inch 400-ohm speakers AD3500 in series, one with a double-cone. An output transformer is switched in when an external low-impedance loudspeaker is connected, it delivers 0.8 W in 5 ohm. There are separate tone controls for bass and treble and a ferrite antenna with separate rods for LW and MW can be turned with a knob. In one end position an outer antenna is switched in. The tubes are ECC85, ECH81. EF89, EF85, EABC80, EL84, UL41, EM80, EZ80. The chassis is the same as Philips B5X61A and H5X63.
Most of the tubes seemed to have been changed recently, only the magic eye was worn and I replaced it with a UM80 with 19 V heater transformer. Almost all "tar" capacitors are replaced as well as two electrolytic capacitors. The tuning capacitor drive was sluggish but I managed to make it work. The simple 3-speed record player Dux 5156 has a crystal pickup for normal- and micro-groove records. The player had to be replaced because the rubber rim of a transfer wheel is dried up and the pickup is faulty so I have put a portable CD-player under the lid. The cabinet looks nice, FM-sensitivity is adequate but the output power is just 2.3 W at the onset of clipping and the sound lacks deep bass, the resonance frequency of the speakers is 90 Hz. The frequency response is 70-8500 Hz at -3 dB and 35-11 500 Hz at -6 dB. I couldn´t say no to the price 25 kr in the second-hand shop.
This Swedish tabletop radiogram Philips H4S03A, made in 1960 in Norrköping under the name "Anita" with original price 722 kr, was a bargain for 25 kr at the summer sales in the second-hand shop. The record player and the amplifier are equipped for stereo but not the radio which has a connector for an external stereo decoder. I have inserted a home-made one powered with a rectifier/doubler from 6.3 V. Although the two side-mounted 6-inch speakers AD3700AM with 90 Hz resonance frequency have 800 ohm impedance the amplifiers have output transformers, a solution which seems puzzling but by using an autotransformer instead of a conventional one with secondary winding it will be smaller and less expensive to make and it has less powerloss. The radio was meant to be used with separate high-impedance speakers and the user's manual recommends Philips HZ 6. The stereo effect is not good with the built-in ones, having the speakers on the sides is a poor idea and the bass response is weak because the amount of air behind the speakers is minimal. The output transformers are spare-coupled with plate voltage on the loudspeaker coils so the three-pole connectors are protected and luckily enough I had two suitable male connectors, probably bought in the 1980's. I have added a switch for the built-in loudspeakers to be disconnected when separate ones are used. The output power is 3 W each channel.
The tubes are ECC85, ECH81, EBF89, ECC83, EL86, EL86, EM84. The FM-discriminator has germanium diodes. Two tubes had to be replaced, among them the EM84, and as usual a number of leaky paper capacitors. The selenium rectifier had a short-circuit which had made a temperature fuse open, so I use silicon diodes and a glass fuse instead. I lowered the heater voltage with a 0.1 ohm resistor and I got rid of 100 Hz hum with the help of an additional electrolytic capacitor plus a 1 H filter choke. The FM tuning capacitor was stuck but released when I heated the shaft bushing with my soldering iron to soften the grease. The same chassis G6a is used in Conserton V7041 and Dux V1411. The record player started after I lubricated the motor shaft but the crystal pickup didn´t give any output so I replaced it with a ceramic GP230.
For just 50 kr I brought this Loewe-Opta Truxa 2731W from the flea market. It was made in 1958, the price then was 485 kr and it represents German middle-class with loudness-type of volume control, separate controls for bass and treble as well as fixed registers so typical of its time: Bass-Jazz-Sprache-Solo-Orch. Besides the UKV-band it covers LW, MW and SW 6-19 MHz. The dial is not adapted to Scandinavian customers, Motala is missing on LW and the UKV-band holds a number of German FM-transmitters. A 26x15 cm front loudspeaker, 5 ohm impedance and 60 Hz resonance frequency, is combined with electrostatic tweeters on the sides which give too weak sound to be useful. The front speaker is attached to the chassis (picture) and the opening in the cabinet is not more than 20x9 cm, it is important with a tight fit against the front and I have added rubber strips. Output power is 2.2 W at the onset of clipping where 50 mV to the gramophone connector is enough. Without activated register buttons and with my inserted 1.8 nF capacitor across the output transformer primary winding the frequency range is 53-8500 Hz at -3 dB and 32-12200 Hz at -6 dB. On the AM-bands a certain increase of treble is made to compensate for the attenuation in the IF-filters. Bass enhances low frequencies, Jazz raises high tones especially at low volume, Sprache raises treble and lowers bass, Solo accentuates midrange frequencies but Orch just brings back the other buttons without any electrical function. The exception is the Bass button which works independently.
The tubes are ECC85, ECH81, EF89, EABC80, EL84, EM80. The ferrite antenna is built-in but in fixed position. The dial. I had to replace two tubes, the heater fuse, the paper capacitors and the filter electrolytic capacitor. The selenium rectifier is replaced with silicon diodes. Just as in my Grundig 3097 there are no trimming capacitors for the SW-band, I had to add one in the antenna circuit for the best result and after that the sensitivity on SW is 7 µV. The front speaker is the best oval one that I have come across and the frequency range of the amplifier matches it but the mounting doesn´t do full justice to it. I have replaced the useless tweeters with conventional ones made by Peerless which make real difference. The radio is named after a well-known Danish entertainer and magician who was popular in Germany at the time.
Siemens Kammermusik-Schatulle M 57 from 1956 isn´t a radio for people who are short of space being 89 cm wide with the doors open and weighs 20 kg. This model was aimed at those who find no pleasure in seeing the lit dial and magic eye but prefer a non-technical look. The combined mains switch and volume control is in front of the doors and when they are closed the dial lamps and magic eye are shut off, only a faint red light near the volume control shows that the radio is turned on. In my two sets the switch for the magic eye is missing but I solved the problem by using a relay activated by the lamp voltage. The dial
This model belongs to the luxury class since it is equipped with a tuned RF-stage, two IF-stages with variable AM-bandwidth in two transformers linked to the treble control and a push-pull amplifier with 7 W output measured at the onset of clipping. The measurement was made across the bass speakers, it is likely that 3 W to the smaller speakers shall be added at 1 kHz. On FM the sensitivity is excellent due to four IF-stages. The SW-band covers 5.9-18.5 MHz. On SW and MW the sensitivity for 50 mW output is 5-8 µV measured with a 200 ohm signal source, but on LW it is only 18 µV depending on intentional damping to achieve acceptable AF-bandwidth. The inductance of the antenna coupling coil is 6 µH on SW, 1.5 mH on MW and 11.8 mH on LW. The ferrite antenna only works on MW, it can be rotated from the front and switched out with a pushbutton. Another button chooses a local station on MW and then the coupling between the RF-stage and mixer is untuned. The power amplifier has separate controls for bass and treble, loudness volume control and a button to switch between Speech/Music. There are separate output transformers for low and high frequencies and two 8-inch full range loudspeakers (6 ohm and 66 Hz resonance frequency) together with two 4-inch ones, all at the front.
The tubes are EC92, EC92, EF89, ECH81, EF89, EF80, EABC80, ECC83, EL84, EL84, EM80. All of them needed replacement but the fixed capacitors and dial lamps were in good condition. Using separate triodes instead of the usual twin-triode meant less radiation from the antenna and less thermal drift of the oscillator. The FM-tuning capacitor was stuck, the tuned circuits needed adjustment and the selenium rectifier delivered too low voltage so I wired a silicon diode bridge in parallel with it. Otherwise the radio is well preserved, a bargain at the flea market for 250 kr. The original price was 848 kr. The mains voltage selector must be in position 250 V.
An strange detail is that the smaller speakers are not mounted directly on the front board but on bent plastic tubes ending up on the front. This causes the high tones to travel a longer distance and creates a phase shift compared to the sound from the bigger speakers. Nowadays we place the elements at the same distance from the listener to avoid this problem but in the mid 1950´s the manufacturers boasted with "space sound" and "3D-sound" in the adverts and this was Siemens´ contribution to acoustical hocus-pocus. In any case the sound is marvellous with deep bass, just as good as that of Philips BX998 below, and the frequency span is 35 Hz to 12 kHz measured at the -3 dB limit.
Luxor Diplomat 399L from 1951 was the top model of that Swedish manufacturer with a price tag of 775 kr. It is an AC/DC-set for which I paid 100 kr, the AC-version is 399W and the circuit diagram is the same as that for model 299 which dates from 1949. Because it has five SW-bands, 11-230 m with some bandspread on the 16-, 25- and 41-meter bands and a good logging dial, it was sought after among dx-ers but in other aspects the radio is in no way remarkable. The sensitivity on SW is 10 µV for 50 mW output, the input is high impedance which works well for an endfed wire. On the LW- and MW-bands the bandwidth is increased in the first IF-transformer, a common fault is that the wires to the switch are mixed up and need to be changed. On the three high frequency SW-bands the oscillator is below the signal frequency which must be considered during trimming.
The tuning mechanism "mikrosving" has two speeds, fine and coarse, with a knob on the right-hand side and it uses a huge flying-wheel. A metal dial string strengthens the impression of quality. The AF section with two 8-inch loudspeakers (resonance frequency 62 Hz) is indeed unconventional with separate power tubes for low and high frequencies, each of which feeds its speaker. This is a solution that Luxor used almost entirely during the 1940´s in their expensive sets instead of conventional push-pull circuit. The audio section has a loudness volume control, tone control and a trap for 9 kHz. The frequency response of the treble amplifier is 560-4800 Hz at -3 dB down and 430-6700 Hz at -6 dB down. The bass amplifier has its lower -3 dB limit at 40 Hz relative 500 Hz. On the front are knobs for loudness volume and tone control. Output power is 2.3 W (bass) and 1.4 W (treble), I raised the latter a bit by removing a capacitor from preamp grid to ground. The tone control is passive, at one end position the left speaker gives an unintelligible growl and at the other end the right speaker howls with the same result, so a position in between sound best. Strangely enough Luxor did not use negative feedback in the AF-section, which explains the rather mediocre sound in spite of the size of the cabinet. The gramophone connector is coupled via a transformer and has 47 kohm across the leads, it is intended for magnetic pickup so a a crystal one needs an impedance interface.
One of the pushbuttons is meant for a local station and a set of coils is plugged into a tube socket. Mine is designed for the middle part of MW (900-1200 kHz). When broadcasts started on UKV in 1955-56 many people bought a separate tuner to connect to the gramophone input. In this particular radio some handy person included the tuner so that its controls are in an aperture on the left side, a unique solution making the radio useful for today´s programmes. The tubes are UCH21, UF21, UF21, UBL21, UBL21, UM4, UY1N. I replaced three tubes and the restoration included replacement of electrolytic capacitors and some flaked resistors. Contact spray was needed in potentiometers and contacts. The plate voltage is increased by means of a silicon diode across the rectifier tube and the filter capacitors now have doubled capacitance. The use of a smaller capacitor to the volume control gave further reduction of hum. The unusual dial lighting uses four 110 V 4 W lamps but the dial is nevertheless unsufficiently lighted, green text over brown background gives poor contrast. The dx-er should have a low chair and keep the radio on a high table.
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Luxor Ambassadör 3098W from 1956-57 is one of the big tabletop radios, 62 cm wide and weighs 17 kg, and it is the successor to the previous 399. The chassis is the same as in the radiogram Aristokrat and by judging from the model names we understand that these sets represented Luxor´s upper class. This one cost 850 kr but I got away with 50 kr at an auction. The sound part is well developed with loudness volume control, separate controls for bass and treble, 7 W push-pull amplifier, two 8-inch speakers on the front and a 5-inch speakers on each side. The receiver part is average with two exceptions, a generous coverage of SW 11.5-210 m in three bands and that the UKV-FM band covers 86-108 MHz. The dial. On the AM-bands a 9 kHz-trap is placed across the output transformer and on SW2 the bandwidth is narrowed in the second IF-transformer. The sensitivity on SW is 10 µV for 50 mW output, the input is high impedance. The inductance of the antenna coupling coil is 5 µH on SW1, 97 µH on SW3, 268 µH on MW and 7.7 mH on LW. The ferrite antenna for MW can be turned from the front, with an external antenna switched in at one end position. There is also a speaker switch to use the built-in ones when Luxor´s tape recorder is connected.
The tubes are ECC85, ECH81, EF85, EF80, EABC80, ECC83, EL84, EL84, EM80. The second IF-stage is used for FM only. Six tubes out of the nine needed replacement as well as the electrolytic capacitor and almost all brown paper capacitors of the brand "Farad", and the selenium rectifier is replaced with silicon diodes. The common stinginess of not using trimming capacitors in the antenna circuits on SW was found here so I added two for best sensitivity. The cords to the tuning capacitor and ferrite antenna were broken, the work to change them was tedious and the bakelite wheel on the capacitor shaft broke during the process. The treble sound was sharp and unpleasant so I modified the negative feedback circuit by removing a capacitor and that made an improvement, the frequency response now being 35-17000 Hz and the radio sounds as good as Telefunken Opus 6.
Philips 940A was introduced in 1934 as a budget alternative to the newly developed superheterodyne radios for those who were content with reception of the national broadcast programme on LW or MW. It cost 145 kr and offered technique from the end of the 1920´s, but somewhat refined. A regenerative detector with E446 is followed by the power tube E443H with 1 watt output to a chassis mounted 14 cm speaker with permanent magnet, and the rectifier is 506. Earlier so called single-circuit receivers had had dials marked 0-100 because the antenna affected frequency, but here the coupling is so light that Philips could use wavelength indication. Regeneration is controlled with a knob through inductive coupling, the position dependent on frequency, and adjusted to just before oscillation. Instead of the usual potentiometer a variable capacitor in series with the antenna is used for volume control. A 100 µV-signal is audible on MW, but on LW a 300 µV-signal is required due to a shunting choke. On the back are three screws, the upper one activates attenuation for those who are in immediate proximity of a transmitter. If one still wants to receive distant stations the middle screw activates a wavetrap on MW and the lower screw a wavetrap on LW. The trap frequencies are set with trimming capacitors on the back. There is a connector with 100 kohm impedance for gramophone, but since there is no volume control a variable resistor is needed in series with the signal. A level of 25 mV is enough and the frequency span is roughly 150-4000 Hz with a resonance peak around 250-300 Hz.
This set had had the filter electrolythics and two tubes replaced. I changed the defective detector tube so that set-up now is E446, P435 and RGN1064. Moreover I replaced a low voltage electrolytic and two paper capacitors. I have replaced two big components with long leads with small ones with short leads in an attempt to reduce hum and I use shielded wire to the gramophone connector. The detector tube is microphonic so I mounted the holder with rubber inserts and made flexible connections to the stiff wires. Plate voltage to the power tube is taken from the rectifier cathode so I added a filter with 470 ohm and 22 µF to eliminate hum, a little of it remains from the directly heated cathode but not annoying. The radio is compact, the width being 31 cm. The cabinet is made of bakelite, that is what makes it differ from the Philips 944A with wooden cabinet that my grandparents had and that I got when I was 15 years old and rebuilt into a morse training summer. At that time a "straight" receiver wasn´t worth saving, but nowadays it is nice to have in working order. The radio was a gift.
Philips 522A from 1934 was the company´s first superheterodyne receiver to be sold in Sweden and cost 295 kr, equivalent to two months´salary. The same circuit diagram is used in Dux V54. The set covers LW och MW and the wavelength is shown in the small celluloid window. The 8-inch loudspeaker with a permanent magnet speaker, resonance is 65 Hz, has the output transformer (8 Hy) attached to it and the connector for external loudspeaker is parallel with the primary winding with plate voltage, so one had better glue a cover over it. There is no switch position for gramophone, one must disconnect the antenna. The tone control is a treble suppressor. The antenna input is high impedance so it is enough with a few meters of wire indoors to pick up foreign stations during dark hours.
The tubes are AK1, AF2, AB1, E446, E443H, 506. I replaced all electrolytic and paper capacitors. The screen grid of the AF preamp needed better decoupling to stop oscillating. The filament cathode of the power tube gives an audible background hum, but otherwise the sound is adequate with about 1 watt output. I replaced the broken rectifier with 1805, the three amplifier tubes are down to 2/3 of new ones but the radio works well all the same. I adjusted the IF-circuits (104 kHz) to 9 kHz bandwidth which gives good selectivity. I have version 1, in version 2 the bandwidth is increased to 13 kHz which also applies to version 4 with 115 kHz IF. The chassis is compact with the IF-transformers placed underneath and tuned with double trimming capacitors on the back. The flea market price was 140 kr, two knobs were missing and the top side was the worse for wear but I managed to fix it.
Tjerneld Super 7 Camping 100 is a battery-powered portable radio from 1938 which then cost 310 kr. It was equipped with a carrying handle and protective front lid and was powered by a 120 V dry battery and a 2 V lead accumulator, both housed inside the cabinet which is covered with artificial leather. The long power cord indicates an accessory mains-operated supply because the anode battery was expensive, in 1958 it cost 23 kr which was the same as for the 6 Ah accumulator for the filaments. Current consumption is 20 mA and 0.75 A respectively. The set covers LW, MW and SW with a connector for gramophone. The dial. The 8-inch loudspeaker has a permanent magnet, the third metal bar in front of the cloth is missing on this radio.
The tubes are 1C6, 1A4T, 1A4T, 1B5, 30, 1E7EG. The chassis comes from Centrum and is of model 32, their corresponding model is JB6 P. While Centrum´s model number means number of tubes, Tjerneld´s number indicates number of tuned circuits, in this case four in the IF-chain and three in the antenna circuit. Tjerneld had close co-operation with Gylling & Co, which in those days used American tubes to avoid patent conflicts. For the same reason the two IF-stages use tetrodes instead of pentodes. The final stage is connected in push-pull and delivers about 0.3 W before clipping starts. On the back there is a switch for reduction of treble, totally uncessary in my opinion.
I replaced capacitors and a few resistors. Possibly the high voltage from a battery eliminator had risen and destroyed the electrolytic capacitors, they were replaced in 1947 and the remains of an exploded one are still visible. Three of the six tubes have been replaced as well. Lightning had burnt the coils for LW, both the coupling coil and the tuned one, but I managed to use the major part of them and the reduced sensitivity on that band (about 45 µV) is a minor problem. On MW I measured the sensitivity to about 10 µV. The inductance of the antenna coupling coil is 1 µH on SW. I got the radio from a friend who saved it from destruction and I have built a mains-connected power supply inside the cabinet.
Philips 796A was made in The Netherlands in 1936, only a few years after the breakthrough of the superheterodyne principle. The model was called Sonata, the most expensive one of the three sets in the Symfoni-series, and the price in Sweden was 410 kr. It is a big cabinet which holds a 10-inch speaker with permanent magnet. The bakelite part housing the dial can be folded inwards to make the upper surface flat, an unusual detail, but the most remarkable item is the joystick which controls tuning (rotate), volume (up/down) and tone (right/left). The big knob outside the joystick is the mains switch and band selector with a position indicator in the upper-right round window. The movement of the joystick is transferred via bowden wires and the tone control also affects the bandwidth by changing the spacing of the coils in one IF-transformer. The tuning control has coarse and fine characteristic, the latter covering a broadcast band on SW. On the rear are three switches, one turns off the loudspeaker, one reduces bass in the Speech-position and one lets you use the power cord as an antenna via a protection capacitor. The joystick is not well suited for shortwave listening, it is easy to lose the station while adjusting the volume, and it is impractical to have to select a band at turn-on not to mention the need to stretch to the rear to reach the speech-control. This Art déco-design was decided on at the expense of function. On the back there is a switch to turn off the loudspeaker but the connector for external speaker had a protective cover because it was wired in parallel with the primary of the output transformer and carried plate voltage, something that was easily changed.
The tubes are AK2, AF3, ABC1, AL4, AM1, AZ1, although a later version used the E-series of tubes. Two tubes are replaced besides the new EM1 whose heater is fed with 6 V from a separate small transformer. A problem with oscillation in the IF-stage was due to the metal paint coating of the tube not making contact with the earthed pin, but I solved it with thin bare wire and careful soldering. Besides LW and MW there is an SW-band, a progress compared to earlier TRF (tuned radio frequency) sets, but an octode mixer tube as oscillator causes a frequency change with variation in signal strength, a problem on the high-frequency part of the shortwave band. I have stabilized the oscillator voltage which helped a bit but not enough, because strong fading causes a station to disappear and return when the wavelength is below 25 m. The IF frequency is only 128 kHz meaning inadequate attenuation of the image frequency on SW so there are twice as many stations received there and a lot of beat notes, but on MW there is a gadget for image suppression and there are double-tuned circuits on both LW and MW. It took a couple of years before the engineers raised the IF to around 450 kHz.
This model is difficult for the serviceman because the components are placed above each other, the rubber wire insulation flakes off when touched and it is unusually laborious to get the chassis out of the cabinet: 12 screws to loosen, 11 wires to unsolder and a special tool must be made to remove the outer knob for bandswitching. However I managed to remove that knob by prying with a small jeweller´s screwdriver, lifting the locking thin sheet-metal from the side. I have replaced the capacitors and added black colour on the dial glass where the original colour was flaked off. The mains transformer which has its primary winding outermost had developed a short to the chassis and when I by mistake connected an earth wire to the antenna terminal the antenna coupling coil on MW was damaged. It resulted in difficult repair of both transformer and coil, it was not successful as the sensitivity on MW is poor, probably due to the new antenna coil being series resonant. On SW the sensitivity varies between 10 and 100 µV for 50 mW output due to capacitive coupling to the mixer grid. On LW where coupling is both capacitive and inductive the figures are 25-40 µV. The inductance of the antenna coupling coil is 938 µH on MW and 12.4 mH on LW. The sound is unusually good considering the age of the radio with deep bass, speaker resonance is 60 Hz and the output transformer is of proper size. I changed a resistor in the negative feedback circuit to improve the high tone response which now has a 9 kHz limit in the gramophone position and with a built-in FM-radio circuit board to the gramophone connector the quality is impresssive considering the age of the radio. Maximum output is 2.2 W at the onset of clipping.
Centrum GU60 was also made in 1936 but it looks older than the previous radio. It is an AC/DC-set, the AC version is GW60. It has LW, MW and SW (18-50 m) and a tuned RF-stage. The high profile cabinet holds an electromagnetic 10-inch loudspeaker mounted on a slanting board. The circular dial is controlled by a two-speed planetary drive. The tone control is a simple attenuator for high tones. The tubes are 6D6, 6A7, 6D6, 75, 12A5E, U30. The mixer tube has no AGC-control on SW so the frequency won´t change with varying signal strength.
Since all tube heaters are in series it is enough that one of the four dial lamps burns out to make the radio stop working. I replaced two bulbs and a fuse, all electrolytic and most of the paper capacitors and I put a silicon diode across the faulty half of the rectifier tube. With a tuned RF-stage the sensitivity is of course good on LW and MW (6 µV) but for some reason worse on SW (16-30 µV). The figures are valid for 50 mW output at 200 ohm signal source impedance. Because the IF-frequency is only 140 kHz there is inadequate attenuation of the image frequency on SW in spite of the RF-stage, so beat notes are heard when the image falls within the same broadcast band. A peculiarity in the circuit diagram is that the RF- and IF-pentodes have their suppressor grids connected to the screen grids. I changed this and the radio works well, it is also easier to repair and nicer to use than the Philips above. However, the sound lacks bass despite the big loudspeaker, the response has fallen 3 dB at 700 Hz and 6 dB at 350 Hz perhaps explained by the absence of negative feedback and that the inductance (5 H) of the output transformer is too small. The upper 3 dB-limit is 7 kHz and output power is 1 W at the onset of clipping.
The original price was 345 kr, one and a half month´s wages for a factory worker. It was the good condition of the cabinet that made me pay 300 kr at an auction, previous owners have treated it carefully and I am pleased that five out of the six tubes measure like new ones.
Centrum W51 is a few years younger than the Centrum above, probably from 1941, also made in Stockholm and exactly alike KW5 from 1939-40. It is thus an older version, in a time of shortage of parts the factory had to use whatever was in stock. It ranks as lower middle class, certainly without gadgets as wavelength indicator and magic eye, but with two SW-bands 13.5-85 m and six-position tone control for reduction of low or high tones and with variable bandwidth in one IF-transformer. The 8-inch loudspeaker has field excitation coil and the resonance frequency is 95 Hz. The dial. This radio has very good sensitivity on LW and MW, 5 uV for 50 mW output with 200 ohm signal source impedance. The SW antenna circuit was designed for a high impedance antenna, sensitivity with my signal generator is not better than 20-40 µV, but stations are well received even with a short piece of wire. The output power is 2 W at the limit of clipping and the frequency response of the AF-amplifier is 95 Hz-11 kHz at -3 dB. The IF-bandwidth is narrow, 4.3 kHz or 5.7 kHz at -6 dB.
The tubes are 6J8EG, 6K7G, 6Q7G, 6F6EG, 5Y3G. In my set the mixer tube is replaced with ECH35 with twice the gain of the original tube, only tubes 3 and 4 are original ones. The IF-tube had its suppressor grid connected to the screen grid but I tied it to the ground. The tubes with the E-suffix are unusual, the mixer tube has its suppressor grid tied to the screen grid and the power tube has its suppressor grid tied to the control grid. I changed electrolytic and paper capacitors and some resistors whose value had increased too much. A mica capacitor and two ceramic trimmer capacitors had developed an open circuit, the switches required cleaning and I added a mains fuse. This radio was a gift (described as "stone-dead") by a friend who believed me capable of giving it new life. The bakelite was ugly but it could be cleaned and polished.
Orion 99 from 1938 comes from Hungary and reflects the fashion of its time with a big-sized wooden cabinet weighing 21 kg. With a price of 575 kr it was the most expensive table-top radio in the production line, designed with continously variable bandwidth in the first IF-transformer coupled to the tone control, double-tuned input circuit on MW and LW, quick-tuning lever, automatic frequency control (AFC) of a strong station on SW and MW, 9 kHz trap across the output transformer and 5-6 watt power to a 10-inch speaker with permanent magnet och 80 Hz resonance frequency. The wave band in use is lightened and the SW-band 16-51 m is marked with lots of station names. The dial. On the front are controls for volume, tone with mains switch and a button for AFC, while knobs for fine tuning and bandswitching are found on the right side. The circle below the magic eye is lightened in gramophone-position. Unfortunately the knobs are not the original ones. In use.
The tubes are ACH1, AF3, ABC1, AF7, AL5, ME4 (=AM1), PV4200 (=1561) and for the AFC-function AF7 och AB2. The power tube AL5 was missing but the others of Tungsram brand are original ones, and with the exception of the magic eye they still hold 75 % of full data. They are marked with the same number that is engraved on a plate that is riveted to the chassis. The choice of tubes were typical for 1936, the first year of manufacture. ACH1 is replaced with a fresh one and I have put in new EF9 and EL6 as substitutes because the old types are expensive, it takes a small transformer for 6.3 V that finds room on the chassis. E-tubes were used in the following year´s model 999. I have added a VHF/FM circuit board inside the cabinet, the AF output being connected to the gramophone intake with a relay. The switch, tuning control and antenna connection are on the back of the radio.
All electrolytic and most paper capacitors are replaced, two missing lamp holders had to be made and the loudspeaker had to be turned a quarter of a turn. A previous owner has changed the single-pole mains switch to a double-pole one. The restoration is almost finished, the AFC needs more work although I have replaced the AB2 with germanium diodes. The sensitivity is about 10 µV, on SW 10-15 µV. The inductance of the antenna coupling coil is 22 µH on SW, 3.9 mH on MW and 17.6 mH on LW. I reduced annoying hum by feeding the heater of the AF-tube AF7 with DC from a schottky-diode bridge with 4.7 mF smoothing capacitor, it lessened the hum to 30 % of the original hum level that must have been there from the beginning. With the tone control adjusted for a near straight response the upper -6 dB limit of the AF amplifier is 8 kHz, with maximum treble there is a 7 dB lift at 3 kHz, both figures related to1 kHz. The frequency dependent feedback circuit gives a bass boast of 4 dB at 40 Hz, but at 50 Hz the undistorted power has decreased to 4.3 W. The sound quality is good, but the bass response is not as good as that in Philips 796A. I was given this radio for free when I bought Graetz at a radio fair. The top of the cabinet needed new varnish and that has been taken care of.
Telefunken "Zeesen" 875GWK is an AC/DC-set from 1938 but not of ordinary design since two components must be changed depending on mains voltage and sort of current, and in fact there is a transformer inside. In one tube socket sits one of two heater current regulators (iron wire in hydrogen gas) chosen for high or low voltage. Another tube socket either takes a resistor combination for DC or a rectifier tube for AC, and in the latter case an auto-transformer with heater winding for the rectifier is connected. The chassis is made of pertinax (the Germans needed iron for the war industry) in a vertical position and one has to remove the front to get access to the parts and wiring. The power supply is built on a piece of wood placed on the bottom of the cabinet.
The tubes are CCH1, CF3, CBC1, CL4 and AZ1. The 8-inch 15 ohm speaker behind the left half of the cloth has a 1 kohm field winding, the connector for external speaker is in parallel with the primary winding of the output transformer and thus exposed to high voltage, but that is easy to change. Bandwidth is adjustable in the first IF-transformer and linked to the tone control which has a switch for treble cut. The volume knob is also the power switch where oddly in is on and out is off, the wavelength switch for LW, MW and SW is on the right side. On the first two bands double input circuits are used which is not common with 460 kHz IF. An "orthoskop" is a tuning aid, showing the longest stripe of light when the station is correctly tuned in.
The previous owner had changed the filter capacitors and replaced the power tube CL4 with EBL1 using a separate 6.3 V heater transformer and I have added one inside the cabinet. Maximum output is 1.6 W at the onset of clipping and the sensitivity is 15 µV. I replaced four ceramic trimming capacitors, a low voltage elecrolytic, a dial lamp and a number of paper capacitors. The inductance of the antenna coupling coil is 9 mH on LW, 12 µH on MW and 0.9 µH on SW, the two last values indicate that a low impedance antenna is the best choice. The speaker cone needed repair and the sound lacked treble so I changed a resistor to raise the -6 dB limit from 3.5 to 6 kHz. The dial glass is inadequately illuminated, especially the green SW band, so I put three white LED´s on the inside of the back cover to improve visibilty. This radio was a gift, the original price being 248 kr.
AGA Europa 51 of 1939 vintage is an elegant Swedish radio with good sound bought at an auction for 100 kr, the original price was 330 kr. Perhaps the name was chosen because the dial on LW and MW holds 160 stations and some 60 are listed on SW. There is bandspread on the 19- and 31-meter bands which facilitates listening to foreign stations but the entire SW-band, 16.4-53 m, is also represented. The dial. The sensitivity is 20 µV for 50 mW output but twice as much signal is needed on the bandspread SW-bands. The inductance of the antenna coupling coil is 0.6 µH on SW, 988 µH on MW and 8 mH on LW. Because the front is dominated by the large dial, the 8-inch loudspeaker with field excitation coil is mounted on a slanting board. The tuning knob has so great reduction drive that the radio has a handle for fast movement of the dial rod, the clutch is released by pinching the two parts of the handle. The tone control has five positions, it also changes bandwidth in one IF-transformer. The bass response is increased by pulling the knob, hardly necessary because low tones are lifted 5 dB around the resonance frequency (65 Hz) of the speaker. Treble response has fallen 6 dB at 10 kHz but there are two positions for even stronger reduction: -6 dB at 4400 Hz and -6 dB at 1300 Hz. Output power is 2.3 W at the onset of clipping.
The tubes are 6J8G, 6K7G, 6B8G, 6V6G, 5Y4G, EM1. Three of the six tubes have been changed, probably in the beginning of the 1950´s. Even the AF preamplifier 6B8G has AGC but with half the voltage. I raised the plate voltage to the magic eye with 100 V for better brightness. I have replaced most of the paper capacitors, added a filter capacitor to reduce hum, changed a resistor and put in a mains fuse. The slow-motion drive for the tuning capacitor proved a failure, however. The knob shaft drives a wheel with a rubber rim and the rubber was worn and hard. I glued a narrow piece of bicycle rubber tube onto the rim, not a perfect solution because I must pull the knob before using the quick-tuning handle but it works passably well. The fact that the cord is a steel wire means that I won´t need to replace it, I wish that all manufacturers were so provident. The screengrids og the mixer and IF-tubes are connected and fed from a voltage divider instead of a series resistor because the magic eye is not intended for high AVC-voltage. I have given each of these tubes a decoupling capacitor and put a resistor between the screengrids.
It is easy to tune in stations, among other things helped by the logging scale, but the low IF (133 kHz) causes quite a lot of beat notes on SW. In that respect this radio was not up-to-date when it was produced, the chassis is from 1937. On LW and MW there is a double-tuned antenna circuit to avoid such problems.
AGA 1771-1 from 1948 is a younger version of the original one from 1946, often called "The long sofa" because of its width 69 cm, and it was dx-ers´ favourite for its sensitivity and bandspread on the SW-bands. It is still a real good radio for shortwave listening with the bands 19, 25 and 31 m marked with both frequency and wavelength. The two major SW-bands cover 13.3-84 m. The dial. There is a separate pushbutton for local station on LW or MW. A tuned RF-stage and variable bandwidth in one IF-transformer give useful sensitivity and selectivity, the former being 3-5 µV for 50 mW output.. The inductance of the antenna coupling coil is 0.7 µH on SW1, 1.4 µH on SW2, 3.4 mH on MW and 10.5 mH on LW. The AF-section was paid attention to with a 10-inch permanent magnet loudspeaker with 50 Hz resonance frequency, 6 W push-pull amplifier, loudness volume control and separate switches for bass and treble so the sound is excellent. The 3-position bass switch gives -6 dB cutoff at 26 Hz, 120 Hz and 440 Hz while the 4-stage treble switch gives -6 dB cutoff at 3.3 kHz, 4.3 kHz, 6.6 kHz and 7.8 kHz. An unusual feature is that the HF- and IF-tubes have AGC-voltage even on the suppressor grids, the latter tube gets its AGC-voltage to the control grid with a shorter time constant than the other tubes.
The tubes are EF22, ECH21, EF22, ECH21, EBL21, EBL21, AZ1, EM4. I replaced five tubes, all electrolytic capacitors, some paper capacitors and some resistors. An oscillation on the most high frequency SW-band gave me much work, this problem also turned up with my second set of this model and I improved earth connections and bypassing. The final solution was to separate the connected screengrids of the RF- and mixer tubes, give each of them a new decoupling capacitor and put a resistor between them. The AF-preamp tube was microphonic but that was cured by changing the screen grid decoupling capacitor. At first I couldn´t make the dial on the bandspread bands show correct frequency but after adding 10 pF to the padding capacitor the 31- and 25-m bands agreed and the 19-m band required addition of another 18 pF padding capacitor. The oscillator plate voltage is now stabilized with zener diodes. The rectifier tube was insufficient so I changed to AZ4 and it reduced voltage drop by 45 V. Certainly AZ4 draws twice as much filament current but the winding is outermost and has good cooling. The radio received stations without an antenna connected (not always desirable) so I covered the bottom with perforated earthed metal foil.
The original price was 641 kr and I paid 400 kr at an auction in 2010. This was my dream radio in 1958 having borrowed it from the used stock of the local dealer, but my parents were not so delighted, it didn´t receive the second program on UKV FM, so there was no deal as it cost 200 kr then. This is my best radio from the 1940´s, when I have set the frequency the station will be heard if propagation allows, and I have included an SSB-detector. When it is in use the AGC to the mixer tube is replaced with a fixed negative voltage. I have added a VHF/FM circuit board inside the cabinet, the AF output being connected to the gramophone lead with a relay. The switch, tuning control and antenna connection are on the back of the radio.
Philips 933A was made in 1943 in Norrköping, Sweden and the price then was 495 kr, eight weeks´ wages for a factory worker. It is a model with LW, MW and SW with gadgets like switch position for local station and variable bandwidth in two IF-transformers (9 or 18 kHz at -20 dB). For LW and MW there are double-tuned antenna circuits, but not on SW. Sensitivity is 15-25 µV for 50 mW output, it might seem rather poor but is due to high input impedance which works well with an endfed antenna wire. The inductance of the antenna coupling coil is 14 µH on SW, 4 mH on MW and 34 mH on LW.
The fold-up dial glass is an impracticable detail, hard to read without a suitable background and with insufficient lighting from the sides. This radio is difficult to pile in the radio closet and before taking out the chassis one must make and mount supports for the rail that holds the pulleys for the dial cord, but these can remain in place afterwards. The advantage is that the length of dial gives good tuning resetability, the logging scale consists of no less than 375 small dots. Notice all Swedish relay stations to the left on the MW band.
The tubes are ECH4, EBF2, EF9, EL3N, EM4, AZ1. Five tubes had to be replaced, I changed the "eye" to UM4 with a separate transformer for its heater. It is unusual that the control voltage for the magic eye is so low that it doesn´t close even for the strongest stations. I moved the connection from the detector diode to the AGC-diode which gives a bit higher control voltage. The same chassis is used in Dux V136 which has the dial on the front to the right of the loudspeaker.
The AF-circuit has a tone switch with three positions Speech, Music narrow and Music broad and a knob for treble reduction. The first two positions connect a 9 kHz trap across the output transformer and the Speech-position reduces frequencies below 100 Hz. The 8-inch loudspeaker has a field excitation coil and 100 Hz resonance frequency. Its sound was surprisingly dull but removal of a capacitor between the plate and control grid of the power tube raised the treble response from 3.7 kHz to 5.5 kHz while the lower limit is 60 Hz, all measured at 3 dB down related to 1 kHz. Output power is 2.5 W at the onset of clipping. I spent much work on this radio, the volume control and almost all capacitors are replaced and the IF-stage oscillated until I had added decoupling components in the plate circuit. Relying on a common capacitor with the mixer tube is poor engineering. The result is a radio that works well. Brochure for 933.
Dux V136 uses the same chassis as the Philips 933A above and was built in the same plant, the only difference being the front dial. Dux models had different cabinet design and were sold in other stores than Philips because Dux had its own sales organization. I bought this radio at a flea market for 50 kr hoping for some useful tubes, but I had to replace all of them as well as the dial lamps. The EL3N was missing in my tube supply so I changed to octal socket and used EL33 which has the same electrode system.
The restoration called for new string, new capacitors and replacement of wires with flaking insulation, contact cleaning and customary trimming. The dial is more compressed but performance is the same as that of 933A, so the comments above about weak deflection of the magic eye and IF stage instability also apply to this radio.
Concerton V488 from 1947 was also built at the Philips plant in Norrköping. It has the typical Swedish design from the late 40´s with a slanting dial, so easy to read without having to crouch down when the radio is on a low table. Light elmwood in the neat cabinet was popular in home furnishing at that time. The three shortwave bands comprise 16.7-20.7 m, 20.7-33.3 m and 33.7-51.8 m, both wavelength and frequency are marked so it is easy to tune in a station with good bandspread of the broadcast segments. Fixed coils (besides those in the IF-transformers) provide very low frequency drift. The sensitivity on SW is 11 µV for 50 mW output. The inductance of the antenna coupling coil is 8.6 µH on SW1 and 2, 10.4 µH on SW3, 875 µH on MW and 945 µH on LW. Some lettering on the dial has unfortunately been lost due to moisture. The sound quality from the 8-inch speaker with permanent magnet and 50 Hz resonance frequency is excellent, much better than the average slanted-dial radio from that decade. The tone switch has five positions and it also changes bandwidth in the first IF-transformer. In position 5 the frequency range at -3 dB is 60-7300 Hz, in position 4 the upper limit has sunk to 6100 Hz and position 3 reduces treble to 1800 Hz and position 2 to 1000 Hz. Both position 2 and 3 have bass response down to 38 Hz. Position 1 is for speech
with the range 400-5500 Hz. I increased the value of the capacitor in parallell with the primary winding of the output transformer from 1.2 nF to 2.2 nF. Output power is 2 W at the onset of clipping but has decreased to 1.2 W at 50 Hz.
The tubes are ECH21, ECH21, EBL21, EM4, AZ1. Two of them had been replaced in the late 50´s together with the electrolytic capacitor but nevertheless I had to put in new ones and now all tubes are fresh. The IF-coils were far off resonance but after trimming them the radio worked on shortwave. With fixed coils there are 17 trimming capacitors and the lack of a service manual and circuit diagram made the adjustments time-consuming. Neither the MW- or LW-band worked, the series-connected antenna coils seemed to be burnt due to thunderstorm. I managed to repair them although with difficulty because the wires are not much thicker than a piece of hair.and I have replaced a number of "tar" capacitors, modulation hum on SW was cured with 10 nF capacitors across the rectifier diodes. The latest addition is a VHF/FM circuit board inside the cabinet, the AF output being connected to the gramophone intake with a relay. The switch, tuning control and antenna connections are on the back of the radio.What I don´t understand is how I can take out the chassis without getting problems with the thin wire to the dial mechanism. The original price was 390 kr but I got off with 50 kr at an auction.
This Radiola 475V from Svenska Radioaktiebolaget (SRA) of model year 1947 was made in 1948, its dial follows the revised bandplan for MW, and with its slightly slanting dial it is an example of Swedish design at that time. The radio has five SW-bands covering 16-51 m with 15 cm of bandspreading of the broadcast segments. Only one of those bands has trimming capacitors, on the four other bands there are just coils to adjust. The antenna is capacitively coupled to the first grid-circuit on SW and the sensitivity there is 10 µV for 50 mW output. The inductance of the antenna coupling coil is 1.5 mH on MW and 6.6 mH on LW.
One of the drawbars chooses a local station whose tuning control on the back moves ferrite cores. The second drawbar is a tone control which affects AF feedback and enhances speech around 1 kHz. Pulling the volume control knob changes bandwidth in the first IF-transformer by controlling the distance between its coils and at the same time treble is attenuated in four steps with capacitors from the plate of the final tube to ground. The frequency response is 64-6300 Hz at -6 dB, with full treble reduction it is decreased to 1000 Hz at -3 dB, 1500 Hz at -6 dB and 3000 Hz at -12 dB. Output is 3 W at the onset of clipping. There is a 9-inch loudspeaker, 4 ohm with 80 Hz resonance frequency, which can be switched off when an external speaker is used. Strangely enough the dial hasn´t got wavelength indication on LW and MW, just station names. The model also exists as ASEA V186.
The tubes are 7S7, 7H7, 7B6, 7C5, EM4, AZ1. My radio had its latest service in 1954 when two tubes were replaced but the others were original ones. I have replaced all tubes but one, the dial lamps, some resistors and almost all capacitors. Each screengrid in the mixer and IF stage is now separately decoupled instead of being tied together.n I had to reduce the value of the padding capacitors in the oscillator circuit to make the dial markings correspond, the idea with bandspreading is to know where one is tuned so it is worth the effort. Now I set the dial rod to the wanted wavelength and the station is heard if it is on the air, such a radio would have been an asset when I was a young dx-er. The cabinet and dial look excellent, that was what made me pay 130 kr at an auction. The original price was 400 kr.
Philips BS596A from 1949 and built in Norrköping, Sweden has five SW-bands 15,4-185 m, that is what separates it from a standard set from the late 1940´s. The 8-inch loudspeaker has a resonance frequency of 93 Hz, the volume control has loudness compensation and the tone control has a position for Speech with reduced bass. The shortwave sections are chosen to provide bandspreading on the 19-, 25-, 31- and 49-m bands, but they lack detailed markings so one has to take notes of the logging scale numbers. The segments 32,5-39,5 och 51,5-56 m are missing. The dial
The tubes are ECH21, EAF42, EBC41, EL41, EM34, AZ1. I replaced three of them plus the magic eye. The previous owner had replaced the filter capacitor and final tube, I completed the restoration by replacing the paper capacitors, added a mains fuse and a couple of trimming capacitors to get the dial readings correct. The final tube gets its plate voltage from the reservoir capacitor which creates a bit of hum so I addad a filter with 2 H and 16 µF to get rid of it. On the SW-bands the antenna connection is designed for low impedance, the inductance on the five bands varying between 0.6-2.8 µH, while the numbers for MW and LW are 4.1 mH and 15.5 mH respectively. Output power is 1.9 W at the onset of clipping with frequency response 105-6800 Hz at -3 dB and 63-9000 Hz at -6 dB. The sensitivity is 10 µV and the IF bandwidth 6.5 kHz at -12 dB and 10 kHz at -20 dB. The original price was 368 kr, I gave 150 kr at a flea market because of the radio´s well-preserved exterior and it sounds as good as it looks. The same chassis is found in Dux V305.
Philips 915X originates from 1940 but this set was made in Sweden in 1942, it belongs to the well-equipped category and was aimed at customers interested in shortwave reception. A tuned RF-stage, variable bandwidth and bandspread of the broadcast bands 13-, 16-, 19-, 25- and 31-meter was certainly a temptation for those who could afford 579 kr. After the first year the price had decreased to 525 kr. During 1939 Philips had launched pushbuttons for pre-set stations, "Linodyne-system", which controls a variable three-gang capacitor consisting of cylinders with moving outer caps. On MW a fraction of the oscillator inductance is also variable, "padding correction". The position of pre-set stations is adjusted with a screw somewhat awkward to reach through the lower side of the pushbutton. Three keys choose stations on LW and three on MW and the remaining three are used for manual tuning on LW, MW and SW (13.8-50.5 m) by means of the upper dial rod. All six pre-sets can be used on MW if that is preferable. On SW there is a knob for fine tuning with a lower dial rod which normally should be placed at a centre position to guarantee the calibration of the main dial. On LW and MW the sensitivity varies between 6-19 µV. On SW the sensitivity is high on the high frequency part of the band, 4 µV, but on the low frequency half the receiver gets almost deaf. It takes 23 dB stronger signal on 6 MHz than on 18 MHz even after I adjusted the inductance in the mixer grid circuit. The inductance of the antenna coupling coil is 10 µH on SW, 1.1 mH on MW and 12.4 mH on LW.
For manual tuning the main tuning knob must be pushed to become active and the bandspread switch turned to position zero. By pressing and turning the bandspreading knob one chooses the wanted SW-band and that deactivates the main tuning knob. In order to make the bandspread dial show the correct wavelength the main tuning must be parked in a certain position for each of the bands. This is done automatically and the position is adjusted with a screw accessible in a hole on the front. Only the coils are variable then. There is complicated mechanics to make everything work and it does so fairly well but anyone who wants to trust the bandspread dial must have a screwdriver ready to adjust the main dial with the help of a known station and that tool is supplied, it is stored on the back of the radio. There is insufficient precision of the main dial pre-set and the bandspread dials do not completely agree even after that. Perhaps the permeability of the coil cores have changed.
Instead of ordinary metal dial rods there are glass rods giving a narrow white line on the dial glass by means of a lamp bulb far behind them, unusual and free of parallactic errors but the rods are invisible in clear daylight making for blind tuning. Station names on the SW dial show what the owner was expected to listen to in the beginning of the 1940´s. The dial.
The tubes are EF8, ECH3, EF9, EAB1, EF6, EL3, EM4, AZ1. The EF8 tube was introduced in 1938 to give low noise in the RF-stage, it is a hexode where an extra grid is placed in front of the screengrid to reduce the screen current and hence the thermal noise. The triple diode EAB1 offers separate plates for detection, AGC-voltage for the IF-stage and delayed AGC to the RF- and mixer tubes, this improves weak signal reception and makes it possible to optimize the control voltage for the magic eye. On the SW-band the AGC is removed from the mixer tube so that fading does not impair frequency stability. A tone switch with three positions also chooses IF-bandwidth of 10, 13 or 17 kHz and moreover there is a treble-cutting knob below the pushbuttons. The volume control has a loudness characteristic, output power being 2.4 W at the onset of clipping. The 8-inch speaker 9602 (7 ohm) with permanent magnet has a resonance frequency of 110 Hz and is equipped with a fixed high tone cone. The speaker can be switched off by the listener who prefers headphones.
It took a lot of work to restore this radio to working condition: lubricating, new capacitors, some new resistors, repair of the volume control, changing wires whose insulation had disintegrated and three new tubes. I reduced hum in the narrow bandwidth position by feeding the heater of the AF-tube with DC. My set lacks vertical ribs in front of the loudspeaker and the Philips badge is missing as well. Advertisement 1, advertisement 2.
The big brother of 915X above and from the same year is Philips 990X, the biggest and most expensive tabletop radio from that manufacturer in the Netherlands. With a weight of 30 kg it is a heavy piece of furniture and the first year´s price 985 kr certainly deterred most customers because in 1941 the price had been reduced to 750 kr. The radio is principally identical with the one in 915X but it has two SW-bands (13.6-170 m). The tubes are EF8, ECH3, EF9, EAB1, EF6, EL6, EM4, 1561. The variable padding inductance is abandoned and the RF-stage has an untuned plate circuit on LW and MW, but instead there are double-tuned antenna circuits on those bands. The sensitivity for 50 mW output with the quality switch in midposition is 6-20 µV on LW and MW and 4-35 µV on SW. The worst case is for 40-46 m where an adjustable coil is needed. With the tone switch in speech/DX-position the sensitivity is 50 % better. The inductance of the antenna coupling coil is 17 µH on SW1, 104 µH on SW2, 1.2 mH on MW and 12 mH on LW.
Band switching and station presets are carried out by a motor and five preset stations can be programmed on any of the wavelengths. The choice of band is made by pulling out the pushbutton and turning it so that its white mark comes in the correct position. After that the station is tuned in with a screw accessible through a hole behind the tuning knob which must be pulled out. A long screwdriver is required and that tool is supplied, it is stored on the back of the radio. Separate knobs are used for main and bandspread tuning. The dial indicators are thin light lines of which one is used on the bandspread bands, illuminated only in SW2 position. The dial.
The cabinet holds two 8-inch speakers 9602 delivering 6 W output. Besides the three-position tone control with switching of IF-bandwidth there are controls for attenuation of bass and treble. The sound quality is good considering the 1940 vintage when the broadcasters did not pass frequencies above 8 kHz. It does not measure itself against the FM-radios of the 1950´s, but it was an advantage not to receive beat notes from MW stations on neighbouring channels or noise from shellac records. The frequency response falls at 6 kHz and at 9 kHz there is nothing left. The 915X has the same characteristics.
Both motor and mechanics caused me trouble and required both lubricating and cleaning of contacts and without the service manual I wouldn´t have managed to make it work. Four tubes and most of the capacitors are replaced. Instead of the 1561 rectifier tube I use a GZ34 on a socket adapter. Originally the panel cloth was light grey but some previous owner has unfortunately dyed it and the Philips badge on the bright metal plate is gone. The motorization results in an unnecessarily complicated radio, it provided nothing but impression but it was fashion of that time. The smaller brother 915X is an equally good receiver with the exception of lower AF power, but one has greater tuning precision with a conventional variable capacitor than their quick tuning technique. The axial shifting of the capacitor is a mere 1 cm to cover the whole band, something that gives poor stability on shortwave. Advertisement.
At an auction I found this premium model Philips BX760X, made in the Netherlands with model year1946. The original price was 725 kr, the most expensive one of the tabletop radios. In this Swedish brochure it was called Stratocruiser and it was described as "the greatest radio ever built by Philips" with "a sound reproduction of extraordinary quality". It has all controls on the sides while the front is occupied by a 10-inch full range loudspeaker 9634 with 70 Hz resonance frequency. The dial glass, which can be folded down during transport, is on top of the cabinet, but unfortunately it lacks a contrasting background. This radio has three SW-bands 13-51 m, MW and LW. A 6-gang variable capacitor has a set of specially cut plates to give unique bandspread of the broadcast bands on SW. The dial. A tuned RF-stage and variable IF-bandwidth 10-16 kHz give the impression of a radio intended for long distance reception, but even the AF-circuit is well developed with a 7 W push-pull amplifier, loudness volume control and a 5-position tone control which also switches IF-bandwidth. Compared with the AGA 1771 from the same year and with the same tubes the sensitivity of BX760X might seem lower, 4-14 uV for 50 mW output, but that is because the antenna input impedance is higher. The inductance of the antenna coupling coil is 10 µH on SW1, 13 µH on SW2, 15 µH on SW3 and 11.7 mH on LW. As an experiment I replaced the RF-tube with EF85 on a socket adapter and that doubled the sensitivity.
The tubes are EF22, ECH21, EF22, ECH21, EBL21, EBL21, EM4, AZ4. The magic eye is behind the left window and the wavelength indicator behind the right one. The circuit diagram is more than usual complicated since the engineer was given a free rein. The AGC-circuits are separate for the IF-tube and the RF- + mixer-tubes to give the best possible signal-to-noise ratio. In the second ECH21 the heptode forms an AF-amplifier as well as a phase inverter with a 3 dB dynamic expander. The latter is achieved by rectified AF-voltage from the output transformer giving the heptode lower control grid bias which means higher gain. The triode is used for AF-AGC which prevents the output power to exceed the limit for 10 % distortion. The audio section passes 40-8300 Hz, a lowpass filter attenuates 9 kHz beat notes from the neighbouring channel on MW and LW and of course noise from shellac records. Another unusual detail is that the IF-tube is used as an preamplifier for the gramophone, the output is taken from the unbypassed screen grid.
I reduced hum from the AF-tube heater by feeding it with DC but some of it remains, probably due to long unshielded wires. The tone control lifts the range 3-5 kHz far too much in the broad position, giving an unpleasant sound, but I flattened the response by changing the value of a resistor in the feedback circuit. Five tubes required replacement as well as the dial lamps and all electrolytic and almost all paper capacitors. It means fiddling with components that are placed above each other in the deep chassis and as a whole this radio is cumbersome to work with because many components are hidden in sealed cans. I had to use spirits and a small file to clean the sockets of the RF- and mixer tubes and the bandswitch contacts. The radio is fairly good for dx-ing, sensitive, with good stability and excellent bandspreading, but how inconvenient it is to stretch ones arms to handle the volume on one side and the tuning on the other. The width of the cabinet is 63 cm.
For radios after WW2 Philips used model numbers that gave information about the set. The first letter stated if it was B tabletop radio or F console radiogram with record changer, the second letter indicated country of manufacture: S for Sweden and X for the Benelux-countries. The first figure indicated price level 1-9: 1 for the simplest little radio, 4 for a middle-class set and 7 for an expensive and well equipped tabletop radio. The radiograms were between 6-8 but in the luxury class 9 I have found only two sets, those which are mentioned below. The second figure stood for model year, 6 meant either 1946 or 1956, and the third figure meant model variant. The suffix A meant AC, U AC/DC and X that the radio was made for AC but prepared to be used with an outboard DC-converter, then the radio contained some extra capacitors to cut voltage transients and a multi-pin mains connector.
After 1957 the second and third signs changed places, a radio was marked B4S81A if it was a Swedish-made middle-class radio from the model year 1958.
Philips BX750A of model year 1955 is a costly radio. Bi-Ampli was an advertising term meant to be associated with extra high sound quality, it implies separate amplifiers and speakers for bass and treble in order to reduce intermodulation distorsion. Luxor used such technique already in the 1940´s but later returned to push-pull amplifiers with the two speakers coupled together. This radio delivers 2 W to the woofer and 1.5 W to he midrange and treble speaker, the cross-over frequency being around 140 Hz. Even though the sound is good it doesn´t create such pressure that one expects from a top class set, something that the manufacturer realized one year later. The best thing about this radio is the 8-inch speaker 9710 with 45 Hz resonance frequency, strong magnet and 10 W capacity. The other speaker, the 6-inch 9768M, has 95 Hz resonance frequency and stands 3 W. BX750A is a stage of development noticeably because the push-button switches lack enough number of poles so that two of them have thin steel wires to work upon pull-switches. Besides, the number of metal screens indicate that the constructor had problems with instability.. The dial.
The 12 tubes are EF80, EC92, EF85, ECH81, EF41, EABC80, ECC83, EL84, EL84, EM80, EZ80, EZ80. The radio has LW, MW, SW and FM-band to 100 MHz. On the AM-bands an EF85 makes an RF-stage with resistive plate load, with FM it serves as an IF-stage. I wonder why the modest IF-tube EF41 was used instead of EF85 with more amplification. A shielded ferrite antenna can be rotated and switched off when an external antenna is connected. Variable bandwidth (8-13 kHz) is adjusted in an IF-transformer linked to the treble control. The antenna connection on the SW-band is high impedance with a 10 µH primary coil.
I replaced seven tubes, the dial lamps, almost all paper capacitors, a number of resistors and three electrolytic capacitors. I added parallel capacitors to the three sections of the filter capacitor and the heater voltage is lowered with 0,05 ohm 4 W. Push-buttons were stuck and required work with kerosine and a piece of rubber hose under the levers. The clutch between FM- and AM-bands was adjusted with a piece of thin copper wire. I made new cords with loops to replace broken steel wires to the pull-switches, it was time-consuming to get the exact length for them. The tuned input circuit for SW has a stuck trimcore and the inductance was so high that sensitivity was heavily reduced, something that the quality control had ignored. I took off six turns and added a trimming capacitor in parallel to the fixed one. With the oscillator working on 10.7 MHz its signal comes through to the detector and creates a carrier in the middle of the SW-band, one more thing to be solved. The radio was a gift saved from the recycling bin, numerous woodworm holes in the bottom bear evidence of long storage in an attic.
My most complicated and competent domestic radio is Philips BX998A, with the same chassis as in the radiogram FX995A. This top model from 1956 shows off with no less than 16 tubes, it was meant for customers with much money, interested in good sound and shortwave listening. The 1956 year price was just under one thousand kr, twice as much as for an average good radio, and the buyer got a 30 cm dial glass with three SW-bands covering 11-180 m, MW, LW, local station on MW and two UKV-choices, with or without squelch. The AM-section starts with a tuned RF-stage EBF80, followed by mixer/oscillator ECH81 and two IF-tubes with detector, EF89 and EBF80. The FM-section has an RF-stage EF80, oscillating mixer EC92, the two IF-tubes shared with AM, a third IF-stage EF85 and discriminator EAA91. The AF-section comprises ECC83, EBC41 and two power amplifiers. The low frequencies are handled by two PL81 in series-ended push-pull delivering 8 W to an 10-inch speaker 9758A with 700 ohm impedance. The intermediate and high tones are amplified by EL84 giving 2 W to a 6-inch dual cone speaker 9768M. Both amplifiers deliver power to an output transformer which is switched in circuit if an external loudspeaker is connected. Finally there are the magic eye EM34 and two rectifiers EZ80. I replaced seven of the tubes and the dial lamps, as to the rest it was enough with lubricating and tuning up because the radio is in mint condition. It is the radio that I paid the most for, 500 kr for 27 kg, and it occupies the place of honour in my house and is often used.
The wavelength selector is driven by a motor, at the push of a button the switch is parked in the wanted position and an indicator lamp is lit. While the motor is running the AF-amplifier is silenced by a blocking voltage. The knob around the magic eye turns the ferrite antenna (separate rods for MW and LW) which is screened for best directivity, and in one end position an external antenna is connected. There are separate controls for bass and treble, the latter being linked to two IF-transformers where the distance between the coils is variable in order to change the AM-bandwidth between 7 kHz and 17 kHz. There is fine tuning on the two highest SW-bands and for local MW-reception there is a separate knob and dial. Because the amplification on the FM-band is higher than usual, noise and weak stations can be a nuisance when one wants to change between local stations. With the choice FM-squelch the oscillating triode in ECH81 delivers a voltage which is rectified in the RF-tube EBF80. The negative voltage is brought to the suppressor grid of EF85 where the amplification and noise is reduced but when a local station is tuned in, a voltage is created which blocks the oscillator and sensitivity is restored to normal. Since this model has two more amplification tubes than an ordinary radio, it is the most sensitive broadcast receiver that I have came across, with a sensitivity of 3 uV on SW. The sound is also among the three best of my tabletop radios, certainly the radiogram FX995A has deeper bass response due to its bigger size but lack of space forced me to sell it.
What is missing is a more detailed shortwave dial with close marks. Because I can´t see what exact wavelength I have tuned in I have connected an external digital frequency display with compensation for the IF-frequency. Moreover I wish I could switch off the magic eye when I don´t need it, so I will put a toggle switch on the back. There is also a need for temperature compensation of the SW-oscillator.
This is the radio panel of the Swedish radiogram Stern & Stern Concerton U584 from 1953. The S&S company was bought by Philips in 1936 and after 1940 the radios were made in Norrköping. The corresponding Philips model is FS744U. It is an AC/DC-set, a beautiful piece of furniture with two lids for radio and record changer Philips 2975 which was launched in 1950 and has separate electromagnetic pickups for 78-turn and microgroove records. The UKV-band is missing of course but the radio has five SW-bands covering 15.4-185 m, variable bandwidth in one IF-transformer, switch position for local station, 3-stage bass- and continuos treble control, loudness volume control and 5 W push-pull amplifier. The loudspeaker (9760-05) measures 28 cm and can be turned off when an external speaker is connected. Its resonance frequency is stated to be 45 Hz but I haven´t checked that. The big screw heads on the front are used for band selection and tuning of the local station, the wavelength of which is visible in a small window behind the dial.
The tubes are UCH42, UAF42, UAF42, UAF42, UL41, UL41, UM4, UY1N. I replaces six tubes, the electrolytic capacitors, most of the paper capacitors and the 19 V dial lamps, lubricated moving parts and repaired the dial drive. Mains wiring with dried insulation had to be changed. The SW-bands 1-4 do not have trimming capacitors in the antenna circuit so I added 4-8 pF on bands 1-3 for best sensitivity and image frequency suppression. I have increased the filter capacitance to 150 uF and put a silicon diode across the rectifier tube. This, together with a bit more idle current in the final tubes, raised the output power to 7 W at the point of clipping. The frequency span was 30 Hz-6 kHz at -3 dB, but I increased the upper limit to 7.5 kHz by using half the value of the shunt capacitors from the plates of the UL41s. With reduced position of the volume control the compensation makes the response flat to 12 kHz.
The record changer did not work well enough so I put in a Garrard RC121D, a flea market bargain for 50 kr. The original magnetic pickup was connected to the radio through an insulating transformer, an unsuitable method for a crystal pickup which needs at least 1 Mohm impedance for good bass reproduction. Therefore I use a field effect transistor as impedance converter. A compact stereo fits in one of the compartments behind the doors and provides output from FM-radio, CD-player and cassette player to the gramophone connector. I bought the radiogram in a second-hand shop for 125 kr although I haven´t got room for it, but it looked so good. Advertisement. The original price was 1420 kr.
Grundig K41 S from 1958-59 is a medium-priced radiogram with an original price tag of 1350 kr. Its chassis is similar to that of Grundig 3097S but has a push-pull amplifier with two EL95 for 7 W output to four loudspeakers, two oval ones on the front and two electrostatic tweeters on the sides. Side view. The tone register buttons are labelled Jazz-Tal-Ork-Sordin around the broad Klangväljare where only the four variable controls are active. The record changer is the four-speed Perpetuum Ebner Rex S Deluxe with crystal pickup for normal- or microgroove. A jalousie shutter hides the radio from curious young fingers.
As usual I had to change tubes, capacitors and tune it up. The rubber lips of the changer´s centre rod must be replaced, they are so worn that they don´t handle a pile of records but a single record can be played. The output of the pickup has deteriorated and I added a preamplifier with a bit of RIAA-compensation but the tone controls have so great range that it is not really necessary. With increased amplification of low tones follows the risk of acoustic feedback because there is no wall between loudspeakers and record player.
Graetz Sinfonia 422 from 1956 was the top model among their tabletop radios and cost 695 kr. On the front there are two oval speakers with 80 Hz resonance frequency and a smaller oval speaker for midrange and high frequences. A so called sound compressor is attached under the top, a horn tweeter whose sound is led in metal tubes to openings on the sides. The "spatial sound" comes from the time delay and corresponding phase shift. Besides the usual bass and treble controls there are three register buttons labelled Speech, Solo and Orchestra and also buttons that turn off external loudspeaker, magic eye and sound compressor including the front tweeter. The ferrite antenna is switched in with a button and can be turned with a knob, another knob switches between narrow and broad selectivity in two IF-transformers. The set has two IF-stages active on both AM and FM, but with low current and therefore reduced amplification. The dial, whose FM-section is adapted för listeners in Germany. The SW-band has only MHz-markings, not much help for finding stations.
The tubes are ECC85, ECH81, EF89, EF89, EABC80, EL84, EM34. Unlike the competitors´ top models there is no push-pull amplifier, but an unusual gadget is that the triode in the magic eye is used for noise reduction on the FM-band. A 50 pF capacitor from the discriminator more or less decouples high AF-frequences through the varying inner resistance of the triode. I have replaced six of the tubes including the "eye", the selenium rectifier is replaced with a silicon bridge and I also had to replace some resistors and capacitors. The sound quality is very good, but when any of the register buttons is pressed the bass and treble controls are deactivated and their lamps are switched off. Sprache accentuates midrange and high frequencies, Orchester emphasizes bass and suppresses treble while Solo boosts both bass and treble, but I prefer the manual settings. I paid 100 kr for this radio at a radio fair.
Graetz Melodia 519 from 1957 is a simpler and a bit smaller version of the Sinfonia above, I guess that it cost about 575 kr. The chassis has only one IF-tube without bandwidth switching and the ferrite antenna is fixed, but the sound compressor for "spatial sound" is there. The two oval speakers have 90 Hz resonance frequency and there is a round 10 cm speaker between them for midrange and high frequences. I am not entirely happy about the sound quality, the tone control circuit is different than that in Sinfonia, the register buttons don´t give the desired result and the bass control has minimum effect. Noise reduction on FM is achieved with negative voltage on the suppressor grid of the IF-tube when the magic eye is switched off. The dial, with the FM-band intended for listeners in Germany. The SW-band covers 16-51 m.
The tubes are ECC85, ECH81 EF89, EABC80, EL84, EM34. Strangely enough the rear covers of both Graetz sets indicate one more tube than the actual number, counting the selenium rectifier as a tube. Unusual is also that the oscillator triode in ECH81 has the tuned circuit at the grid rather than at the plate, something that often causes frequency drift on SW during fading. I got this radio for free when I bought the Sinfonia, the top of the cabinet and the lower front needed grinding of the veneer and new varnish. I have replaced five tubes, the eye is now a UM4 with voltage doubling rectifier for the 12 V heater, and the selenium rectifier is replaced with silicon diodes which required a series resistor to reduce the increased voltage. It would be an improvement if the button that deactivates the magic eye lowered the heater voltage to 2 V instead of turning off plate voltage, the cathode emission would last longer.
Telefunken Opus 6 from 1955 was at that time their finest tabletop radio with six loudspeakers, two 8-inch ones on the front and in each rounded front corner a 4-inch one with permanent magnet and a 2.5-inch electrostatic tweeter. The AF-stage is push-pull with separate controls for bass and treble and loudness volume control. The output power is 6 W when clipping starts, the 3 dB-limits of the frequency response are 30 Hz and 11 kHz. The AM-bandwidth can be narrowed in two IF-transformers with a button and the recommended procedure is to start with the narrow choice to get right on spot. The second IF-tube is not connected to the AGC-line and draws only little current. The sensitivity for 50 mW output is 6-10 uV on SW. There are separate pushbuttons for gramophone and tape recorder inputs. The ferrite antenna for LW and MW can be rotated with a knob and an external antenna is connected in one end position. The UKV-knob offers gives bandspread on SW (KW-Lupe) and the dial rod shall then be placed in a centre position for correct calibration.
The tubes are ECC85, ECH81, EF89, EF89, EABC80, EC92, EL84, EL84, EM80. I replaced dial lamps and almost all tubes, the magic eye being replaced with an EM85 which required wiring change at the tube socket. Some leaky coupling capacitors and an electrolytic capacitor were changed and the keyboard contacts needed cleaning spray. With silicon diodes across the selenium rectifier the plate voltage rose with 20 V to 250 V. The cabinet had deep scratches in the veneer on the top, that is why I only paid 50 kr for the set, but it has been taken care of. Its sound is excellent and compares with that of Luxor Ambassadör.
Telefunken Opus 9 from 1958, within easy reach from my armchair, is a broad-shouldered German in the upper price range. It cannot fully stand comparison with the sound quality of my best radios however, in spite of two oval speakers on the front and on each side one conventional speaker plus one electrostatic tweeter. Round speakers simply sound better than oval ones. Five pushbuttons affect the sound reproduction: Intim softens high tones while Jazz enhances them, Solo increases the medium range and Bass the low tones. Orchest. gives a flat response and activates the controls for bass and treble but the treble response is not Hi-Fi: -6 dB at 6 kHz, -12 dB at 8.5 kHz and -18 dB at 11 kHz. Therefore the best sound comes with the addition of the Bass and Jazz buttons. The output power of the push-pull stage is 6 W at the onset of clipping. A separate button selects a tape recorder input. The dial. The chassis is almost identical to that in Opus 6 with the exception of the fixed tone registers.
The tubes are ECC85, ECH81, EF89, EF89, EABC80, EC92, EL84, EL84, EM84. Two IF-stages are used for both AM and FM. The AM-bandwidth can be switched to narrow with a button that changes the amount of coupling between the coils in two IF-transformers and cuts off the tweeters. The result is 5 kHz at -6 dB compared to 13 kHz in position broad. On the SW-band where bandspread is provided by the UKV-knob (KW-Lupe) the sensitivity varies between 6-10 µV. The ferrite antenna for LW and MW can be rotated with a knob and in one end position an external antenna is connected. A nice feature is AFC on the FM-band which I haven´t seen on any other tube radio. The tuning knob has three white buttons and when any of them is pressed down the frequency lock is released.
I replaced three weak tubes, four leaky capacitors and two fuses and I put silicon diodes in parallel with the selenium rectifier to eliminate its voltage drop. My price was 400 kr, half of the original one 798 kr in 1958.
Beside the radio is a three-speed Philips gramophone 22GA214 from 1974, a flea market bargain for 50 kr with a ceramic stereo pickup. Both 78-turn records and modern LP´s give a pleasant sound in Opus.
A Real Radio has a lighted dial glass with station names, a magic eye and shortwave band, and it is used not only for local reception but with an external antenna for listening to foreign stations. It uses tubes and should not be missing in any well-furnished home. What charm does a Far-Eastern made plastic box provide?
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E-mail: lenradio (a) bahnhof.se Latest update:20th Sept, 2021