N9EWO Review :
  Philmore / LKG - MW122A Regulated Power Supply
 Modified for use with : Grundig Satellit 800,
Eton e1, Drake SW-8, Sangean ATS-909X2

The low cost Chinese MW122A "117 VAC transformer type" regulated power supply can be modified for STABLE use with the Drake SW-8 , Grundig Satellit 800 , Tecsun HAM2000, eton e1, Sangean ATS-909X2 receivers that can require a pretty good amount of current at 9 VDC (for a portable). As stock it operates way too hot at 600 ma current draw and I would expect failure in time if modifications are not done (let alone a fire). We removed the unstable selector switch (now 9 volt output only) , changed the secondary transformer tap for cooler operation. Now no more headphone hum (Sat 800) and much more stable output . Once modified we found it to be a very useful and clean supply for these receivers .

NOTE : Availability became more limited in early 2017. Only USA importer in March 2021 is Philmore - LKG Industries of Rockford ILL (sold by various US dealers for around $ 35. to 40. but some are selling it at excessive prices beyond this. Do your own internet searches and look around including ebay.). (N9EWO Photos)

I will NOT be held responsible for any info that is listed here.

The MW122A Regulated Power Supply : Modified for use with the Grundig Sat 800, Tecsun HAM2000, Eton E1, Drake SW-8, Sangean ATS-909X2 receivers.

WARNINGS : The following information and modifications are for the person handy with basic electronics and soldering skills. Of course pass this up totally if you are not, or find a friend who is !! DOING THE FOLLOWING IS TOTALLY AT YOUR OWN RISK . I WILL NOT BE HELD RESPONSIBLE FOR ANY NASTY PERSONAL INJURY AND OR FRIED EQUIPMENT FROM USING THIS INFORMATION !!

Testing another UNMODIFIED MW122A sample with the Sangean ATS-909X2 (and with that receiver ONLY), the transformer tap change part of the modifications below is not required as it current requirement is much less. Heatsink only gets warm for normal radio operations as stock out of the box. However is still NOT suitable for battery charging purposes (best to use a external charger anyway) ! So IF you wish to trust the semi-flaky voltage selector switch it can be used as stock with the ATS-909X2 (just add the proper connecting DC cable, see cable accessory information below).

A low cost regulated "higher current" power supply, but not cool out of the box even at 600 ma current.

Drake SW-8, Grundig Satellit 800, Tecsun HAM2000 and eton e1 portable receivers all operate on nominal 9 VDC and require a good healthy 600~700 milliamps (ma) of total current for proper operation. The Sangean ATS-909X2 also requires good clean 9 volts for operation (however uses no where near 600 + milliamps) but this modified AC adapter works great here too (
WARNINGS : NOT to be used for the battery charging function and is NOT suitable for the older X version with the modifications as given here !).

The included UNREGULATED floor/wall warts are all rated at 1 amp of current and even at full load give over voltage to the set. So the receiver internal voltage regulators must work harder with more "voltage burn off" difference and this is in the form of excessive heat from these regulators. In the case of the Sangean ATS-909X2 it's included wall wart adapter is of a "RF noisy" switching type (totally unacceptable).

If one operates the eton e1 for a few hours using it's included AC adapter one will feel this excessive heat on the rear side around the DC jack. With the Grundig Satellit 800 and Tecsun HAM2000 its harder to detect, but feel on the top part of the cabinet just above the S-Meter after being on for awhile. It's on the warm side and any PC board is quite a ways from this point. But you get the idea and excessive heat is never a good thing in any electronic device.

Of course the solution for less internal regulator heat is to just use a nice 9 VOLT REGULATED linear-transformer type supply that is good for at least 700ma of current . Of course using any low cost switching type supply (or a linear one that uses switching regulators) is not a good idea with any Long-Medium-Short wave receiver !! That is unless you love self-inflected interference.

Good Old Headphone Hum With Included Power Supplies

Another issue that makes it very desirable to use a regulated supply is the fact the internal audio amplifiers normally do not see any of the filtered current from the lower voltage internal regulators in the receiver. It's just the raw voltage off right off the external DC jack. So one can hear a background hum especially with headphones in use. Have verified this in the eton e1 and Grundig Satellit 800 and it drives me crazy. Using a regulated power supply will eliminate this.

Tough finding anything "9 Volts , Regulated, Linear , Pre-Built" and at a higher current (or any current for that matter).

Now the real problem is finding such a power supply as "pre-built" off the shelf (but not too big either). One could be build from scratch for those handy enough, but at a high cost if you have to purchase most of the parts. In the past we have used and recommended some of Jameco's linear regulated power supplies wall warts, however after my own experience they have started to use very noisy switching regulators in these adapters (without any word that it was changed...nice guys). So that takes those off the list fast (sorry Jameco).

OK, so we see this MW122A multi voltage "high current" regulated transformer linear supply around. In fact this is the ONLY such regulated linear power supply to have enough current that we have been able to find. UPDATE : In the USA it's now (research as of March 2021) only distributed by LKG-Philmore and via it's US dealers. This power supply uses a LM317K type regulator (TO220 case) attached to a large heat sink to it's rear panel. Thank goodness this is NOT a RF noisy switching type adapter !

IMPORTANT NOTE : There is (was ?) a 220/240 volt version of this supply marked as the MW2122A model. Sorry , I cannot say if this is 100% identical and will these issues and/or mods still be valid ?? You are totally on you own with this one (and do your own web page searches for more information).

Runs Way Too
HOT as Stock at only 600 ma current !!

But however it's not going to be that simple I'm afraid. It looks good enough on paper and while it can be used as is out of package.......well at least for awhile (not recommend as we will cover next). Because after some time in operation the rear heat sink (LM317K IC Regulator) becomes extremely HOT at 9 Volt operation with any of these receivers. In fact it's gets so hot that if you touch the rear heat sink, I would expect one to receive a major burn !!

Another issue we have experienced with one sample was with the voltage selector switch that was very flaky. Jiggling it slightly did not always give the desired voltage (it went all over the place), but it would also erratically jump to it's unregulated voltage in the 20 + VOLT area too. Later tested samples were better in this regard, but would YOU trust it in time ?? Not good here in my view, and I simply will not trust it this way !

This low cost switch arrangement is comprised of finger leaf contacts (that are on the plastic voltage adjustment knob) that rub up against the pc board for contact. No wonder it can be flaky.

This rotary voltage selector adjustment internally actually switches 2 circuits at the same time when rotated. First side of it selects the proper resistor for selecting the LM317K's output voltage (resistor RX5). Second side selects the proper secondary transformer tap which is supposed to select a lower voltage to keep the input voltage to the regulator more proper (less heat) .

In practice it falls way short and still too much transformer secondary voltage and
HOT operation. So it's time to pull the plug from the wall and remove it's 4 screws to access the internal parts.

IMPORTANT NOTE : Joel T.  informs that his late 2016 sample used "Security Type Screws" instead of the standard Phillips type  screws that were on both of our test samples. He had the proper "fork" type screwdriver to get it opened, but this could be an issue without the proper tools. This power supply is (was) sold in a number of slight variants over the years , so this finding may vary (may or may not be a problem).      

The PC Board before and after the modifications. We remove the totally unstable selector switch. You can see my 2 added RED wires (after the removal of J1 and J2 jumper wires). One on the Transformer secondary wire to the 6 volt tap. The other added red wire to the RX5 resistor as shown. The 3 PC board screws (that need to be removed) are slightly hard to get at . See my hand scribbled notes here for more information . (N9EWO Photo's)

Time For The Modifications

So first what we did is to remove the switch from it's front PC board (3 screws on the PC board holding that are a little difficult to get to and put back, but is not too bad). One screw holds the entire switch assembly. Next I removed the 2 bare jumper wires from the mid part of the board. After that we added 2 insulated jumper wires as to hard wire it for more stable and cooler 9 volt ONLY operation.

Second to help reduce the power supplies heat sink heat, we found in extensive testing that using the 6 volt secondary transformer tap (yes for the 9 volt output) gave more than enough over voltage for proper LM317K regulator operation.

An alternative for the "transformer jumper wire" would be to skip this one and instead just move the RED pc board 6V tap wire over to the hole connection near the voltage bridge rectifier (see photo above, where the one side of the jumper wire is just below the rectifier) .

See my hand scribbled document here for additional information.

A few important notes :

- "Quality Control" (as it is on many low cost Chinese products) is fair to poor on these. We found the internal binding post nuts to be very loose on our latest test sample. So poor connections for sure here. So better have a look see at these as well as all other solder connections etc...etc.... before you close it back up.

- Power transformer in this beast runs extremely
hot at even "no load" status. So watch out for that if you open it up after using it for awhile.

- When putting it all back together the hardest part will be replacing the 3 PC board screws to the front panel and getting LED back in place while struggling with all of the transformer wires all at the same time. It's a tight fit. Make sure the PC board is straight after it's screwed down and in place (don't bend it, it's NOT a fiberglass board of course).

Still Not Real A Cool Supply But Now Tolerable , No More Hum with the Satellit 800

These modifications will NOT make the MW122A's rear heat sink run real cool by any means with the Grundig Satellit 800 , but it is still much improved over stock and less of a chance for the internal LM317K regulator getting burned out and dieing (and maybe even kill the connected receiver too). You will now be able to touch the heatsink with these modifications (at least for a few seconds) now without getting a nasty burn.

We can now listen to headphones without hum and with less cabinet heat with the Satellit 800 (and much less heat stress on internal parts).

A couple of final WARNINGS !

I would NEVER EVER try and obtain anywhere near rated TWO Amps of current out the MW122A (let alone even ONE amp), at least not without a fire extinguisher handy as it will probably catch fire ! But for the application we cover here at the 700 ma max current , it's just fine and very useful after the modifications . Remember just NOT to place it on any carpeted surface (give it lots of air under and around it) . Of course make note of the proper plug and tip polarity (+) as you connect it up . AGAIN DO NOT USE THIS SUPPLY FOR ANY BATTERY CHARGING PURPOSES (too much current required with that function).

Philmore 48-400 Connecting Cable

Philmore- LKG offer a handy and recommended connecting cable for the MW122A. This hefty 18 AWG cable has color marked spade lugs on one end (as shown on the top picture on this page) and a socket for the included 6 different type of connecting plugs of the other. WARNING : This is also where one selects the tip + or - for the plug depending what way you plug it in. Be sure it's properly set BEFORE use (use a voltmeter to be 100 % sure).

Philmore 48-400 connecting cable which works excellent with the MW122A power supply. Beefy 18 AWG cable with 6 power plugs. Improperly shown here, but the spade lug ends do have positive and negative plastic markings (see picture on the top of this page).

Note : Some USA Philmore dealers do not carry this connecting cable that do sell the MW122A power supply. Of course any DC connecting cable can be easily made as well.

Dave N9EWO
N9EWO, all rights reserved
ver 4.2

I will NOT be held responsible for any info that is listed here.

To find a local or Internet Philmore dealer (click here, USA only)

You Tube Video : Review of a MW122A 2 Amp multi-voltage linear power supply (shows the unacceptable voltage switch and we say 700 ma MAX at 9 volts).

You Tube Video : MW Regulated DC Battery Replacement Power Supply

Choosing a linear power supply for rx-only (also N9EWO's recommendations with power supplies and ratings / heat)

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