Macintosh LC Help

[mooplef]

I recently recapped my Mac LC power supply and motherboard.

The power supply works great, but only sometimes. I can leave it for an hour and I get no voltage on any of the rails, but then I check on it an hour later and it works fine again, full voltage on all of the rails. I didn't replace either of the AC caps, only the DC ones, and whenever it does work, it makes a faint clicking sound and it smells like . . . fish? That's the only way that I could describe the smell. The smell goes away once it's powered off for a few minutes.

The motherboard used to make the startup chime and loop before I replaced the caps, but after, there is no startup chime at all and there was no video signal either before or after.

I have quadruple checked to make sure that all capacitors are facing the correct direction and they are all the right values and high quality capacitors. Any help would be greatly appreciated!

 

[Nycturne]

The fish smell is one I still remember from high school. Some capacitor is failing, possibly leaking. Seems like you are on the right track, but still need to track down the failing capacitor.

I'd also be checking voltage at different points in the power supply to make sure there isn't a short or something involved that's bypassing the outputs. It'll also likely lead you to the bad capacitor.

 

[Garrett]

If you've replaced all the caps in the power supply, it sounds like you need to clean it again. Some residual "fish" smell may be impossible to get rid of, but I suspect a cleaning will solve your problems (electrolyte fluid is conductive). Take the PSU out of its case and soak it in IPA (just enough to submerge the PCB, don't soak the transformers). I also like to scrub with a toothbrush here to make sure I can get in the hard to clean spots too.