5.1.1. GENERAL. - This radio equipment has been constructed of materials
considered to be the best obtainable for the purpose and has been carefully
inspected and adjusted at the factory to reduce maintenance to a minimum.
However, a certain amount of checking and servicing will be necessary to
maintain efficient and dependable operation. The following section has
been written to aid in checking the equipment.
5.1.2. ROUTlNE INSPECTION. - Routine inspection schedules should
be set up for periodic checks of this equipment, This inspection should
include examination of the mechanical system for excessive wear or binding
and of the electrical system for electrical defects and deterioration of
components. If the routine inspection of the equipment is carried out faith-
fully, the chances of improper operation of the equipment are greatly minimized.
It is suggested that this inspection be made as frequently as possible,
and it should be sufficiently thorough to include all major electrical
circuits of the equipment as well as of the mechanical portion.
a. CLEANING. - The greatest enemies of uninterrupted service in equipment of this type are corrosion and dirt. Corrosion, itself, is accelerated by the presence of dust and moisture on the component parts of the assembly. It is impossible to keep moisture out of the equipment in certain localities, but foreign particles and dust can be periodically removed by means of a soft brush and a dry, oil-free jet of air. Remove the dust as often as a perceptible guantity accumulates in any part of the equipment. It is very important that rotating equipment, such as variable condensers and tap switches, be kept free from dust to prevent undue wear, Likewise, variable condenser plates should be kept free from dirt to avoid flashover. One of the greatest sources of trouble in equipment located in a salty atmosphere is corrosion. Corrosion resulting from salt spray or salt-laden atmosphere may cause failure of the equipment for no apparent reason. In general, it will be found that contacts such as tap switches, tube prongs, cable plug connectors, and relay contacts are most affected by corrosion, When it is necessary to operate the equipment in localities subject to such corrosive atmosphere, inspection of wiping contacts, cable plugs, relays, etc., should be made more frequently in order to keep the equipment in good condition.
b. VACUUM TUBES. - Make a check of emission characteristics of all tubes. After making the emission check, examine the prongs on all tubes to make sure they are free from corrosion. See that all tubes are replaced correctly and fully in their sockets, and that a good electrical contact exists between the tube prong and the socket. Use caution in removing and replacing grid or plate caps on tubes so equipped. Before a tube is discarded, make certain that the tube is at fault and the trouble is not due to a loose or broken connection within the equipment. A complete set of tested tubes of the same type specified should be kept on hand at all times. If faulty operation of the transmitter is observed and tube failure suspected, each tube may be checked by replacing it with a tube known to be in good condition. Defective tubes causing an overload in pover circuits may usually be located by inspection, It will be found that excessive heating or sputtering within the vacuum tubes is a good indication of a fault in the tube circuit. If tubes have been in use for a period of time equal to or exceeding the manufacturer's tube life rating, it is suggested that they be replaced. A marked improvement in the performance of the equipment is usually noticeable after the weak tubes have been replaced.
c. PRECAUTIONS FOR SATISFACTORY TUBE LIFE.
(1) Before removing any
tube from the equipment, make certain the primary power is disconnected
from the equipment.
(2) Operate all tubes
within +/- 5% of rated filament voltage.
(3) Do not exceed the
rated plate current of any tube during normal operation of the equipment.
d. TUBE REPLACEMENT PRECAUTIONS.
(1) All tubes are removed
by pulling them straight away from the chassis. Some tubes have hold-downs,
be sure these are loosened before pulling on these tubes.
(2) Remove plate cap
connectors from tubes with great care to prevent breaking the seal around
the plate cap.
(3) Before inserting
a tube make certain it is of the correct type for the socket into which
it is to be placed.
NOTE Changing master oscillator tubes (V001) may cause a slight change
in master oscillator calibration.
e. TUBE TABLE.
SYMBOL | TYPE | FUNCTION | RATED FIL.VOLTAGE |
V001 | 6SJ7 | Master oscillator | 6.3 |
V101 | 6AK6 | Buffer amplifier | 6.3 |
V102 | 6AG7 | Frequency multiplier | 6.3 |
V103 | 7C5 | Frequency multiplier | 6.3 |
V104 | 7C5 | Frequency multiplier | 6.3 |
V105 | 4D32 | Power Amplifier | 6.3 |
V201 | 6SL7 | Audio Amplifier | 6.3 |
V202 | 6SN7 | Audio driver | 6.3 |
V203 | 807 | Modulator | 6.3 |
V204 | 807 | Modulator | 6.3 |
V30l | 5Z4 | LV Rectifier | 5.0 |
V302 | 5R4GY | HV Rectifier | 5.0 |
V303 | 5R4GY | HV Rectifier | 5.0 |
V304 | VR75 | Bias Regulator | --- |
V305 | 0A2 | Screen Voltage Limiter | --- |
V306 | 0A2 | Screen Voltage Limiter | --- |
f. RELAYS. - All relays should be inspected at
regular intervals. Check the contacts for proper alignment, pitting and
corrosion. Use a burnishing tool to clean contacts - never use sandpaper
or emery cloth.
5.2. TROUBLE SHOOTING.
5.2.1. GENERAL. - The most common cause of improper operation of
radio equipment is tube failure. Refer to paragraph 5.1.2.,
b. in this section for comments concerning vacuum tube replacement.
Defective tubes causing an overload in power circuits may usually be located
by inspection. High voltage arcs may be caused by bent condenser plates,
corrosion or dust. Corrosion resulting from operating the equipment in
a salt laden atmos- phere may cause failure of the equipment for no apparent
reason. In general, trouble encountered in radio apparatus can be isolated
by means of various tests and measurements; then the section of the transmitter
in which the trouble is located can be determined. If this is done, the
components in the associated circuit may be checked and the trouble located.
Refer to the tables of meter readings and resistance measurements. No one
but an authorized and competent service man equipped with proper test facilities
should be permitted to service this equipment.
5.2.2. FUSES.
a. GENERAL. - This equipment is supplied with
fuses of the correct rating in each position. Defective fuses should be
replaced by spares only after the circuit in question has been carefully
examined to make certain that no permanent fault exists. Always replace
a fuse with the rating specified by the following table.
SYMBOL | LOCATION | TYPE | RATING |
F301 | LV Power supply primary | Cartridge (3AG) | 3 amp. |
F302 | HV Power supply primary | Cartridge (3AG) | 5 amp. |
5.3. ALIGNMENT.
5.3.1. GENERAL. - If the exciter stages get out of alignment for
any reason, it is recommended that the unit be realigned at once. Improper
operation may result in damage to valuable equipment.
5.3·2· HIGH FREQUENCY OSCILLATOR. - Should trouble
develop in the high fre- quency master oscillator, the unit should be returned
to the factory for servicing. However, the unit can be serviced and realigned
by persons under- standing such techniques providing accurate test equipment
is at hand. A crystal controlled frequency standard with outputs at 1700
and 2000 kc with an accuracy of better than .015 percent, must be used
for setting the band edges.
a. PROCEDURE.
(1) Apply power to the
transmitter and let the MO warm up for about 30 min. then check the oscillator
frequency on a receiver. Operate the transmitter with the emission control
in the CAL position and the key closed.
(2) Couple a receiver
to the output of the oscillator.
(3) Set the vernier index
to exact center of the dial window.
(4) Tune receiver to
output of 1700 kc freq. standard.
(5) Rotate MO to vicinity
of 3400 kc on the exciter dial, and zero beat with the signal from the
standard. Jot down dial reading for use as a reference.
(6) Rotate the MO dial
toward 4 mc exactly 12 turns.
(7) Tune the receiver
to the 2000 kc output of the standard.
(8) The MO should zero
beat with the 2000 kc output of the standard at exactly 12 turns of the
MO dial.
(9) If such is the case
but the dial reading is incorrect, loosen the set screws in the oscillator
coupler and turn the dial to the correct reading (4000 kc), after which
tighten the set screws again. If the MO does not zero beat with the standard
at 4 mc, proceed as follows:
(10) Read the kc difference (the difference between where the signal appeared and where it should have appeared after 12 turns) and multiply it by 5.
Add this figure to the actual beat note dial setting if the beat note was less than 12 turns or subtract it if the beat note occurred at more than 12 turns.
Now set the dial to this new frequency, remove the trimmer plug from the top of the oscillator, and turn the adjust- ment until zero beat is again reached.
It will be found that the high and low ends are very nearly 12 turns apart.
Repeat the above procedure until such is the case; remember that a new reference point will occur at the low ends of the dial each time.
Reading at which beat note should appear after 12 turns of dial = 4002 kc
Actual dial reading = 4003 kc
Difference frequency (4003 - 4002) 1 kc
Multiplied by 5
5 kc Subtracted from 4003 (since beat note occurred at more than 12 turns) = 3998 kc
After setting dial to 3998 kc and zero beating the MO to the standard
with the trimmer
adjustment, the low end beat note should appear at 3398 kc.
Reading at which dial should appear after 12 turns = 3998 kc
Actual dial reading = 3996 kc
Difference frequency (3998 - 3996) = 2 kc
Multiplied by 5 = 10 kc
Added to 3996 (since beat note occurred at less than 12 turns of the dial) = 4006 kc
After setting the dial at 4006 and zero beating the MO to the standard
with the trimmer
adjustment the low end beat note should appear at 3406 kc.
(11). After the oscillator
has been adjusted to cover the range 3400 to 4000 kc in exactly 12 turns,
the coupler set screws can be loosened and the dial set on frequency.
NOTE: The above method of adjustment is used
at the factory. This is a short-cut method and proves very reliable. Actually,
the object is to get the 1700 kc and the 2000 kc outputs of the oscillator
exactly 12 turns apart. The objective can also be attained by using the
slower method of moving the trimmer capacitor in one direction or the other;
then checking results until the desired answer is obtained. Be sure to
replace the trimmer cover plug after alignment.
NOTE: Somewhat greater accuracy can be obtained
if the oscillator end points are set by using harmonic operation, i.e.
listen in the 14 or 28 mc region for the harmonics of the 1700 and 2000
kc signals and set the corresponding harmonic of the MO to zero beat with
these. Do this only after obtaining a very close adjustment as outlined
above.
5.3.3. MITLTIPLIER STAGES, - Should the grid drive to the final
fall below 5 ma on the meter due to change of tubes or aging of components,
the transmitter r-f circuits should be realigned. Proceed as outlined below
only after the master oscillator has been checked and recalibrated as outlined
in paragraph 5.3.2.
A small fiber screwdriver and a 1/4" open end
wrench are required for these adjustments.
a. PROCElDURE.
(1) Remove the transmitter
from the cabinet and tip it up on end. (RF section up.)
(2) Remove 3 access covers
from perforated shield.
(3) Remove the fuse from
the hV primary. (This allows the low voltage supply to be turned on while
the W supply remains turned off.)
(4) Turn the LV and HV
power switches Om,
(5) Place the CW-CAL-PH
switch in the PH position.
(6) Place the METER selector
switch in the GRID position.
(7) Adjust for maximum
grid current, using the adjustments and conditions listed below in order
from top to bottom of the list. (Refer to figure 5-1 for adjustment identification,)
ORDER OF BAND SW TUNING ADJUSTMENT SET AT SET AT ADJUSTMENT
1-- l0M 28,800 3 Slugs marked "28.8"
2-- 40M 7,300 C150
3-- 40M 7,200 1 Slug marked "7.2"
4-- 15M 21,600 3 Trimmers marked "21,6"
5-- 20M 14,250 3 Trimmers marked "14.4"
6-- 80M 3,750 kc 1 Trimmer marked "3.8"
NOTE: In item 4 under ADJUSTMENT, the mistracking
of the third multiplier plate circuit will result in low grid current when
the main tuning dial is set much outside the limits of the amateur 20-meter
band (14 to 14.4 mc). Proper grid current can be obtained at any frequency
on the range 12.8 to 16 mc by adjustment of trimmer C139 (marked 14.4 on
the third multiplier.)
NOTE: If extensive multiplier alignment has been
necessary, it is likely that the two spurious signal traps will need tuning,
Do not touch the spurious signal tuning condensers unless this is so, since
these adjustments are very critical. C149, the spurious signal trap tuning
condenser for the 80-meter band, is located on the side of the multiplier
unit next to C150, see figure 5-4. These traps are tuned as follows:
With the transmitter aligned as indicated in
the above paragraphs, tune the transmitter for 3.5 mc output and listen
with a receiver to the 1.75 mc output. Watching the receiver "S" meter,
tune C147 for minimum signal. Then tune the transmitter up on 7.15 mc and
listen on 3.575 mc with the receiver. Adjust C149 for minimum signal. Both
of these adjustments will be very sharp and care should be taken that they
are not disturbed in the least after the adjustments have been made. Replace
the multiplier bottom cover.
5.3.4. MODULATOR BIAS ADJUSTMENT. - The modulator bias can be adjusted
by turning the screwdriver slot equipped potentioater R305. For best distor-
tion characteristics, the static, or resting, modulator platecurrent should
be 55 ma with the 600/700 v switch in the 700 v position. Potentiometer
R305 is located within the top of the cabinet near the filter capacitors;
therefore the interlock switch will have to be held closed while making
this adjustment. Take great care to avoid touching any components carrying
high voltage. The proper bias for the modulator grids is approximately
minus 25 volts.
5.4. LUBRlCATlON. - The following parts should be lubricated annually
or whenever the need arises by brushing a thin film of the indicated lubricant
on the points of mechanical contact. Don't over-lubricate,
a. Panel Bushings: MOBILE PD535A (Socony Vacuum
Oil Co.)
5·5. OSCILLATOR TUBE REMOVAL. - Replacing an oscillator tube
requires the breaking of the seel around the shield and it will then become
necessary to reseal the shield. If it becomes necessary to replace an oscillator
tube, use a glyptal cement or a generous application of Duco cement to
reseal the shield.
5.6. DESICCANT CAPSULE. - A silica-gel tube is mounted on top of
the oscillator shield. The silica-gel absorbs moisture from within the
oscillator and aids in retaining the oscillator calibration. Moisture causes
the color of the silica-gel to change from blue to pink. The silica-gel
tube is screwed into a hole in the shield. The plastic tube should be replaced
by a new tube of silica-gel when all material within the tube has changed
from blue to pink. New tubes of silica-gel may be ordered from the Collins
Radio Company.
NOTE: The seal around the oscillator tube shield
and the silica- gel tube is more easily broken if the parts are warm. This
can be done safely with a light bulb or infra-red lamp placed close to
the oscillator.
R.F.
PIN |
3.5
|
7.0
|
14.0
|
21.0
|
27.2
|
28.0
|
G1 1 | -17 | -16.5 | -1.0 | -0.9 | -1.0 | -0.9 |
K 2.7 | 1.0 | 1.0 | 2.9 | 2.85 | 2.85 | 2.9 |
P 5 | 235 | 230 | 230 | 225 | 225 | 225 |
G2 6 | 155 | 150 | 65 | 65 | 65 | 65 |
R.F.
PIN |
3.5
|
7.0
|
14.0
|
21.0
|
27.2
|
28.0
|
K 1,3,5 | 2.6 | 2.6 | 3.9 | 3.2 | 3.4 | 3.2 |
G1 4 | -19 | -18 | -36 | -36 | -38 | -36 |
G2 6 | 215 | 215 | 205 | 205 | 205 | 210 |
P 8 | 230 | 230 | 220 | 220 | 225 | 225 |
R.F.
PIN |
3.5
|
7.0
|
14.0
|
21.0
|
27.2
|
28.0
|
P 2 | 235 | 235 | 215 | 210 | 215 | 215 |
G2 3 | ||||||
G1 6 | -24 | -23 | -56 | -21 | -69 | -51 |
K 7 | 25 | 25 | 27 | 27 | 26 | 26 |
R.F.
PIN |
3.5
|
7.0
|
14.0
|
21.0
|
27.2
|
28.0
|
P 2 | 225 | 220 | 215 | 215 | 215 | 215 |
G2 3 | ||||||
G1 6 | -115 | -110 | -170 | -175 | -150 | -150 |
K 7 | -59 | -56 | -52 | -52 | -51 | -50 |
R.F.
PIN |
3.5
|
7.0
|
14.0
|
21.0
|
27.2
|
28.0
|
G2 2 | 285 | 300 | 300 | 300 | 295 | 295 |
K 4,5 | 0 | 0 | 0 | 0 | 0 | 0 |
G1 6 | -120 | -100 | -93 | -105 | -105 | -102 |
P CAP | 690 | 680 | 690 | 690 | 690 | 690 |
4D32 Plate Current = 220 MA | EP = 700 V Key Down |
Key Up | Key Down | |
Plate E | 820 | 740 |
Plate I | 0 | 220 |
Screen E | 300 | 300 |
Pin | PH | CW |
1 G | -0.6 | -0.8 |
2 P | 88 | -0.9 |
3 K | 0 | 0 |
4 G | 0 | 0 |
5 P | 100 | 100 |
6 K | 0.8 | 0.8 |
Pin | PH | CW |
1 G | 0 | 0 |
2 P | 235 | 235 |
3 K | 7.4 | 7.4 |
4 G | 0 | 0 |
5 P | 235 | 235 |
6 K | 7.4 | 7.4 |
Pin | PH | CW |
G2 | 235 | 0 |
G1 | -25 | -25 |
K | 0 | 0 |
P | 740 | 740 |