Smoke From PSU Socket

I think the first thing you need to do with that one is to find out what the output voltages should be _and which pins they're on_ so you can see just what it is, or is not, doing. A 'tweeting' PSU is generaly one that is trying to start up, detecting a problem, and then hutting down again, Possibly due to bad capcitors (often, but not always, on the output side. Maybe an overvoltage problem (so the crowbar circuit is tripping). Possibly a problem with the shutdown circuitry itslef (there isn't really a problem, but the shutdown is being triggered anyway) -- but whateveryou do, don't be tempted to disable protection circuits. I did once, when younger and more foolish, and ended up with transistors blown apart, metled track, and many other things to repair. I've yet to fidn a really good book,web page on this. The way I learnt was to read the scheamtics and circuit descriptions of every docuemtned PSU I could find, to read all the data shets on the control ICs, etc. It is very difficult in my experience to repair an SMPSU without a schematic. You may be lucky and spot the bad component, but most of the time you need to work through the schematic logically. Alas the scheamtics of most modern-ish PSUs are unobtainable. I gnerally resort to tracing out the full schematic, then interpretting it, and only then starting to fix the thing. -tony