[Kenwood] Re ASTRON PSU RM50

[w4upd]

One thing I don't think was mentioned before was what the voltage under 
was to regulator input? We know that your output essentially goes to 
zero with load on the output. What is the voltage going into the actual 
pass transistors? Also, check voltage on the filter caps at this time. 
If voltage on the output after the pass transistors is low, but input is 
still higher (ex. 16 - 20vdc), then the problem is regulator circuitry. 
If the input to the pass transistors drops as well, then your problem is 
before the transistors. I would then suspect transformer (not too 
likely), bridge rectifier, etc.

Reid, W4UPD


On 11/12/2016 1:41 PM, Tim Billingsley wrote:
> Thank you for the insight.  I am beginning to think my best option is to
> take pictures of everything,  make diagrams, and start pulling it apart and
> build it back from scratch.  LOL
>
> Thanks again
>
> On Nov 12, 2016 03:02, "ROLAND HOWELL" <snowy.howell at btinternet.com> wrote:
>
>>   Hi TimI have repaired a couple of these in my time, the first one was an
>> interesting one, multiple faults on it. The first of which was 18v AC on
>> the top of the large smoothing cap/regulator board, this turned out to be
>> the 2 very large rectifier diodes on the back, 1 x O/C the other S/C,
>> replaced those and that sorted that problem, now have 36v DC on the top of
>> the smoothing cap.Then I couldn't get the 723 ic to perform, so replaced
>> that and as an added measure all of the small caps dotted (electrolytic and
>> low value types), always replace the cap ( if my grey cell is working, I
>> think its 100pf) between the higher number pins on the 723).That's good now
>> have 13.8v at the output, but, ( there's always a but huh), it was unable
>> to supply more that a few amps.
>> This turned out to be most of the pass trannies emitter wiring, dry
>> jointed, apparently this is a common problem with ASTRON PSU,s. Having
>> remade those soldered connections, all is now well. As an after thought
>> test each emitter connection by pulling gently on it, it may look ok but I
>> found that the best thing was to remake all of them.
>> The main smoothing cap is prohibitively expensive here in the UK, but,
>> ASTRON were very good and put me onto their parts dealer who shipped me a
>> couple here ( including a free mains switch! you don't get that here! ) to
>> the UK for a lot less.
>> The 2nd one was just the soldering of the pass trannies.
>> Hope that helps, used in conjunction with other advice on here you will
>> get it up and running in a little while
>> RegardsSnowy G0HZE
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