[Kenwood] Re ASTRON PSU RM50

[ROLAND HOWELL]

 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