So in order to replace the fan on my Molar, I took the PSU out and it was *filthy*, absolutely caked in dust. So I used a combination of paper towels, Q-tips, 99% IPA, and a small cordless vacuum to clean out most of the dust. While reassembling the molar after replacing the fan, I decided to also max out the RAM and install a VRAM SIM, and install a CD ROM player. Well, after reassembling all of that, I get no chime, no light, and the fan runs. No degauss either. Ok, don't panic, maybe it doesn't like the RAM. I brought it down to one stick and removed the VRAM SIM, no change. Removed the CD ROM, no change. I get good voltage on the +5 and +12v rails. I don't get any voltages of note on the neck board. Tried removing all the RAM, no crash noises or any other change. Tried random sticks in random slots, no change. Reseated the voltage regulator, ROM, and CPU a couple times. No change. Reseated all the PSU cables several times.

My guess is somehow the alcohol hurt something, the vacuum hurt something, or I damaged something with my aggressive Q-tipping, or the RAM or VRAM totally borked the logic board. I'm gonna try firing up the LB with an ATX power supply tomorrow, but I'll take any advice in the meantime. Any schematic for this power supply would be helpful.

And it's back. Probably a cracked solder joint or maybe some alcohol hadn't fully evaporated. Or it wanted to spite me. Whatever the case, works great now.

I have what I suspect is a bad PSU with one of my Molar Macs. Not sure the state of the analog board / flyback, but I need to disassemble it again to dig in. I'd love some more info on these to troubleshoot the power supply. Where did you measure the 12/5v voltages?

>> wottle said:

I have what I suspect is a bad PSU with one of my Molar Macs. Not sure the state of the analog board / flyback, but I need to disassemble it again to dig in. I'd love some more info on these to troubleshoot the power supply. Where did you measure the 12/5v voltages? Click to expand...

Just off the molex connector that connects to the disk drive splitter cable