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Old 01-09-2022, 10:52 PM   #1005
momaka
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Default Re: The Hall of Shame - Badcaps Photo Montage

Quote:
Originally Posted by PeteS in CA View Post
Look like the cause was something other than the caps. I think Nichicon discontinued the PL series something like 15 years ago, so they had a pretty long life.
Concur.

Actually, I do have a theory of what might have happened there. Being that old, those Nichicon probably had deteriorated rubber seals at such age. If at some point the PSU was "bumped" or exposed to slightly stronger vibration, that could have caused some electrolyte to leak out. Moreover, the PL series are somewhat similar to the PR series of that age in that they both used the quaternary ammonium salt in their electrolyte. Now, the PR series were actually pretty well-known for leaking electrolyte from their bungs after a number of years. PL, on the other hand, not anywhere near as often.

So basically, I'm speculating here that these Nichicon PL caps started to leak a little bit of electrolyte on the PCB. Since electrolyte is quite corrosive, it probably started eating traces away. Over time, it could have caused a weak or bad connection somewhere. On top of that, electrolyte is also conductive and flammable too. So if you have a weak connection and you add a conductive agent to it (possible source of spark or heat generation) that's also flammable... I think that might explain how the small inferno happened inside the PSU. Or does that sound like a big tinfoil hat theory?

And in any case, the big question is: why didn't the PSU's protection circuitry shut it down?
All in all, that PSU doesn't look like a cheapo no-name dubious brand. But perhaps it just lacks/lacked modern protections (aside from maybe complete short-circuit)?

Last edited by momaka; 01-09-2022 at 10:54 PM..
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