VOGONS


First post, by vbug

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Hi everyone, I have some old toshiba T series PSU not working, model PA2478U, 18V 1.7A, and I would try to repair them. There is no current at all on the output. First I checked the output cable, it is in good condition. On the inside everything looks in perfect condition, no oxydation, no bomby capacitor, the 2 fuses on the 220v side are okay. I have no idea of what could be wrong with those PSU, so any suggestion or idea would be welcome. Thanks !

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Reply 1 of 6, by Thermalwrong

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vbug wrote on 2025-01-26, 09:11:
Hi everyone, I have some old toshiba T series PSU not working, model PA2478U, 18V 1.7A, and I would try to repair them. There is […]
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Hi everyone, I have some old toshiba T series PSU not working, model PA2478U, 18V 1.7A, and I would try to repair them. There is no current at all on the output. First I checked the output cable, it is in good condition. On the inside everything looks in perfect condition, no oxydation, no bomby capacitor, the 2 fuses on the 220v side are okay. I have no idea of what could be wrong with those PSU, so any suggestion or idea would be welcome. Thanks !

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Right, looks like I missed this. I fixed one of these a couple years ago and I thought I took pictures but I can't find them or anything written down for what I did.

Looking at yours on the underside of the PCB there is clear evidence of electrolyte leakage which has started damaged traces. You need to clean all that up.

The big high voltage cap does not fail. Those two big brown caps on the DC side are good quality ones and they were not leaking on mine.

My PSU looking at the cap codes, it appears I replaced the C10 capacitor (35v 47uF, at the edge of the PSU PCB in between those two sideways mounted sub-boards) with a modern rubycon.
I also replaced C13 (25v 220uF, by the two big DC capacitors under the heatsink, by the blue&yellow inductor thing) and from what I recall that was the bad one that had leaked everywhere, also replaced with a modern rubycon cap.

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Hopefully your PSU has the same problem, make sure to clean up all the electrolyte / brown that you can see with IPA.

Reply 2 of 6, by vbug

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Thanks @Thermalwrong, you're right there is evidence of electrolyte leakage, I ordered new ones, I'll replace them when received and keep you updated.

Reply 3 of 6, by vbug

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So on two PSU I replaced C10 and it fixed it, but on a third one after replacing C8-C9-C10-C13-C15 it still don't work, I'm wondering if I should try to replace the two big 25V 820µf.

Reply 4 of 6, by vbug

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I finally replaced the two big 25v 820µf, one of them was leaking, but after that the PSU still doesn't work, as I replaced all electrolytics capacitors I don't know what I can do now

Reply 5 of 6, by Thermalwrong

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vbug wrote on 2025-03-01, 10:55:

I finally replaced the two big 25v 820µf, one of them was leaking, but after that the PSU still doesn't work, as I replaced all electrolytics capacitors I don't know what I can do now

No idea sorry 🙁 The ones I've fixed so far only needed that.
You could just get another PSU to replace it - doesn't have to be the original Toshiba one but 19v at 1.58a is one type I spotted that seems common and I think would work, assuming the plug fits.

Reply 6 of 6, by vbug

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SO I re-fused all capacitor solder point and re-cleaned the board with IPA and now it works ! Thanks again for your advices @Thermalwrong 😉