I'm looking for some advice on what you do with my Astron 35A power supply. It sometimes trips out at about 20 amps. Here's the exact experience: It's probably about ten years old. It powers my Elecraft K3. I don't really use it much but when I do, it's usually on a digital mode which at about 40 watts, draws about 10 amps so I wouldn't normally notice the problem anyway. My club uses it and the K3 once a year for field day so I'm mostly concerned with getting it fixed before next field day. In the last few months, I think since last field day, I've been operating and the radio has instantly switched off. I don't have much test equipment but I think I've properly concluded that it's the power supply tripping out, not the radio. I powered my little QCX radio from the same power supply and I can see a very brief flicker on its display at the instance the K3 goes off. Last week I was able to cause the fault to happen repeatedly. I could tune up the K3 and then key down at about 90 watts which is about 19 amps and all was good. Then increase the power. Every time when I got to 95 watts or about 20 amps it would trip out. I read this https://www.ecse.rpi.edu/courses/CStudio/ham_radio_docs/astron-repair-index.htm . I've looked inside and there doesn't seem to be any obvious mechanical issue. The connections to the pass transistors seem good. I gave up, put the top back on, put it under the desk and then it was working fine at 23 amps which is about the most I can make the K3 draw. I haven't used it all week until yesterday I tried it and it tripped out once but now it seems to be okay again. Is this an obvious mechanical problem / bad solder joint that I just haven't found or is it possible that a transistor or the 723 could be intermittent? Should I go for the sledgehammer approach and replace all the transistors and the 723? That's easy enough to do and won't cost a lot. The transistors are 2N3771 and the 723 is in a socket. I really need a better dummy load. Some people suggest a car headlamp. Using a $1500 radio to as a test load might not be the smartest thing to do. I discovered that if I tweak my manual antenna tuner a little, I can make the radio draw a little more current. I think that's why sometimes, even if the fault exists, I can run full power without problem. Full power is just on the threshold and the exact current drawn by the radio depends on the exact tuner settings / SWR. Thanks for any advice.