As I'm having no luck at all with searching myself (maybe I'm using the wrong terms, but everyone seems more interested in going into depth about how inductors work rather than repairing the PSU itself) I'm hoping someone here can offer me some insight or point me in the right direction. Basically, my brother and I are repairing old computers as something of a hobby. He intends to use them, I just like fixing them. We've run across two PSUs, however, which neither one of us knows enough about to be able to fix: one is from an Apple IIe (an Astec +AA11040-B "gold box" unit) and the other from a Sega Saturn ("long" 5-pin unit), representing basically opposite ends of the spectrum for flyback SMPS units. The Apple PSU is completely non-functional. Plug it in, turn it on and there isn't even a blip of output on any of the DC lines. We've replaced all of the electrolytic capacitors (often cited as the first step, since they're 35+ years old), the DC rectifier diodes, and the X-type polypropylene cap which looked to have split its case on both sides. We also pulled every transistor and hooked them to one of those $20 transistor testers and it identified them all correctly (which at least means they're not completely dead), and checked what I believe to be the start-up resistors (R2 and R3, both 100Ko) out-of-circuit. This unit hasn't worked as long as we've had it (since the mid 90s). The previous owner seems to have abused the system (most the screws were missing, many of the ICs had rusted legs, and the PSU fuse had been replaced with aluminium foil) so we can't be entirely sure that something nasty hasn't happened to it along the way. But "everyone" (search results) seems to insist it should be fixable and that instructions exist on how to do it - just that I've not been able to find any. The Sega PSU, on the other hand, has only recently failed. In isolation (so the console is not at fault) it will run perfectly for around 15 seconds before the output voltage on all three rails rises and the unit cuts out with the power light blinking. When the outputs rise the feedback from the DC-side shunt regulator falls, which we assume is causing the rise (we've replaced the regulator without success). Once it does this, the unit has to be left for around 2 minutes to "reset" before the process can be repeated. Unlike the Apple, my brother has owned this since new in the mid-90s (just a coincidence), so we know its usage and service history (light-to-moderate and none respectively). It seems to have had a slow failure over the past few months where it once cut out after an hour or so, before it would cut out during a game intro (Torico for those playing at home) and now only lasts for the start-up period on the TOP202 control chip. As such there aren't any obviously damaged components like you'd expect from sudden failure, so we need a better means of diagnostics. If anyone can offer some advice on how one (or both) of these units might be repaired or at least diagnosed, I'm all ears. And if you can point me to at least a moderately comprehensive guide to repairing SMPSs, which doesn't get bogged down on inductors, I'd also be appreciative as these will doubtless become more common as we progress to repairing 32-bit systems. Cheers.