Macintosh II (IIfx?) 699-0393 power supply capacitor list?

willmurray461

Well-known member
I know you're trying to fix a II; are you trying to rule out whether the PSU is broken? Have you tried jump starting the computer? If you short two of the pins on the PSU, you can start the machine (I forgot which ones, but you can look it up). This will let you know if the PSU is dead or not. Just make sure to only do it a few times at most, since it may damage the motherboard if you do it too many times.

I've owned several II/IIfx and I've never come across a dead PSU. As such, I'd say it's pretty unlikely the PSU is the culprit. Most likely a corroded trace on the PCB preventing the startup circuit from working.
 

thisisamigaspeaking

Active member
I know you're trying to fix a II; are you trying to rule out whether the PSU is broken? Have you tried jump starting the computer? If you short two of the pins on the PSU, you can start the machine (I forgot which ones, but you can look it up). This will let you know if the PSU is dead or not. Just make sure to only do it a few times at most, since it may damage the motherboard if you do it too many times.

I've owned several II/IIfx and I've never come across a dead PSU. As such, I'd say it's pretty unlikely the PSU is the culprit. Most likely a corroded trace on the PCB preventing the startup circuit from working.
It powers on (but doesn't chime) when I press the power button on the back. I am going to recap the logic board and I was thinking of doing the power supply while I'm at it. But if that's not likely to be broken, maybe I'll skip it.
 

Juror22

Well-known member
But if that's not likely to be broken, maybe I'll skip it.
I've only have 6 Mac II adjacent (II, IIx, IIfx) units and I've not had a failure either, but I have had to replace a fan and I took the time to clean all of them inside and out. I agree that re-capping the logic board is going to be your first priority.
 

nathall

Well-known member
FWIW, I have a IIfx power supply that was stored in a non-water tight shed for several years. The case is all rusty. Yet, it still works perfectly, fan and all. It was bad enough I sanded off most of the rust so it wouldn’t blow rust chunks on an unsuspecting logic board.

I have two IIsi power supplies that were stored with loving care. Neither one worked when I pulled them out last year. I recapped and restored one, the other continues to actively disintegrate.

Those IIfx supplies seem to be made of titanium. The guts, anyway.
 

Iesca

Well-known member
Does anyone have one handy to show where the two little standup, screw-on shields are supposed to be? I neglected to take a photo of the larger of the two in particular.
 
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