Nodding... True...Max, practise on junkers first. Oh, bit about the fan jump a bit with power removed. I'm 100% certain something is shorted in the secondary outputs and by the way most of time usually has none of scr or clamp downs to block overvoltage, the PWM ic usually '494 and LM339 monitors the output voltages. Remove the main transformer and check all diodes for dead shorts and leaky capacitors ONLY in the output side, about 6 or 8 diodes and few large 470uF or 330uf or so in 12V part and larger ones for the 5V part. The fan jumping was the switcher ic trying to spin the transformer into one of the short circuit but switcher also have self-protection circuits kept it from spinning until main power is removed. Don't be fooled, at least 2 diode pairs are in two "transistors" casings, but there's markings that looks like two diodes back to back. Both of those "trannies" are always mounted on heatsink. One is large for 5V and one looks like TO-220 case for 12V and few discrate diodes for negative voltages rated at very low currents, sometimes taps off the -12VDC via a regulator on tiny heatsink of all itself to drive the -5VDC. I'm certain this PSU of yours has no "Power Good" wire, that is controlled by same LM339 that monitors all 4 voltages or usually 2 voltage levels and come up on power good wire in delayed fashion after all the voltages is up. Excellent beginner info to surf. Go there. :) But this does not beat the info if you really trace out where all the outputs out on that PSU and pick out most likely components to check with your meter and catch the baddie red-handed. Pure joy when that happens! :) Before I got the ESR, I had to play the game of who's is bad on either caps or semis or both. Sometimes I just go out and swap all the outputs caps right there and there. :) But now that I got ESR meter, the worry is over and this is a MUST to have because the cost is so cheap. Get one from "Bob Parker's" DSE's ESR meter kit from under and to the left without a second thought. Bragging rights/Boasting aside, I had to use my friends contacts to obtain very specific components and rely heavily on subs. :-( Boo hiss. :) Jason D. Jason D. jpero(a)pop.cgocable.net

But Max later said when he pulled the power he noticed about a second later the fan jumped. I have seen that before too. That also would not work when either secondary caps and diodes components is shorted. That is what it's like when PSU tries to spin into a low resistance load but PWM noticed that and kept off but when power is removed the PWM disconnects from safety shutdown mode as input power by that mains filter decays causes PWM to run at lower power but enough to make fan jump. That is not what I meant, PSU are supposed to be loaded always for proper operation and shorted components adds up to lower resistance that trips the PWM controller safties. But with all the loads removed, that PSU is running on that shorted diode as a resistance load at just right resistance. That would be very unusual to me in PSU but someday I would run into these but I only dealt with common stuff, I only saw one or two machines that used this 2 lead in TO-220 case. Not USUALLY. :) Cheapo and in good stuff usually does not mark very well. Use your eyes on circuit layouts and components # used to pull down docs off the net if needed. Remember, most guys have no OSCILLSCOPE. :-( Mayor $$$ and very slow to aquire one. Or you're done "zapping" one and putting back that "good" but now blown caps, adding to the confusion. Also I don't relish doing that and can't hear the tiny pop or zapping sound. Oh, I tried to obtain the "Television" from a special inporter mag reseller but they can't find or get them. Well, develop one and make code freely available with circuit layout then otherwise could anyone obtain that cicuit layout and send some to interested party like me. That one thing but I meant usual parts like caps, specfic semi components and such that is easily available in US and some places in canada but none in my hometown, has to rely on substitution heavily. True...byond that most semis not those jellybean ones are what I need and most places have those jellybeans but not those I need. For ASIC's, I resorted to collecting large # number of similar boards that uses same chipsets and take good ones to repair high quality boards. Jason D. Jason D. jpero(a)pop.cgocable.net

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