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After a break I proceeded as described above. After cleaning the board again, replacing the rifas, schottky and optocouper, I gave it a try. Unfortunately it did not go well... As soon as I switched the power on, there was a bang again (louder this time I think). The LV was probably still...

So, next to replace are: The schottky was full of cap gunk and I broke the leg myself cleaning it

here is the board It seems one of the rifa cap has a crack on the side I have no way to know if that's what popped. I understand the board should anyway work fine with failed rifas (i.e. this is not what causes the low voltage)? I will still look for a proper replacement (Kemet PME295...

Well, bang is maybe a bit overly dramatic, but there was definitely the kind of short popping noise that you don't want to hear in electronics. I'll have a look at those capacitors, thanks. The optocoupler is new. I still have some spares, I could see if swapping it for another new one changes...

Hello, here's an update. The logic board was cleaned, recapped and repaired by a very kind forumer who contacted me to offer to do what I was surely unable to myself. Many thanks to him! Unfortunately, I was probably too eager to try my mac and should have - as suggested - cleaned the analog...

After a few tiny adjustments of PP1 I now have 12.3V / 5.12V / -12.16V. The Mac boots straight away and the screen is not as wobbly anymore. Good! Next step is then recapping the logic board, which will hopefully prevent future issues and fix the sound.

I gave another try today and decided to leave the mac runnning a little bit longer. After a while, the zebra stripes disappeared, the HDD spun to life, and the computer booted ! The screen remained very wobbly for some time (maybe 5-10'), but eventually all was almost normal. The sound did not...

... and now that I think about it, that is probably the issue I was having 10 years ago when I stopped using it. This seems to be a case of "simasimac"

I am making progress! I replaced all components mentioned above and checked connections. The Mac will now power on. However I get no bong, and the display remains gray and shaky: I measured low voltage at 4.8 V / 11.97 V. Am I looking now at issues with the logic board or could it still be...

ok, just ordered those parts to replace next (after having gone through a number of threads discussing similar issues): DP3, DP4 diodes - 1N4148 QP1 Optocoupler - CNY17G-3 DP11 5.6V zener diode - BZX79B5V6 IP1 Chip - TDA4605 QP2 MOSFET - IRFBC40

Thanks, indeed 😁 I did not reflow them, but I tested the continuity from pin to pin with my multimeter. I guess it will not hurt to do it, but I am not convinced that there is no other issue unfortunately.

Thanks to both for your replies. The fuse and the solder joints of the power connector are fine.

Hello everyone, My beloved Mac Classic used to work until about 10 years ago. It then started to fail booting, with a gray screen. I never looked into it (due to lack of time), but recently decided to try reviving it. I have started by cleaning and recapping the analog board, and cleaning the...