jmacz
Well-known member
I've been taking a look at @techstep 's Quadra 840AV which has been having some boot/post issues. I need some additional suggestions.
Setup: the motherboard, PRAM battery installed, memory installed, connected to speaker, connected to original power supply, connected to 13" Apple monitor, no drives attached.
Symptoms: push the power button, PSU fan spins up, voltage seems to be coming to the motherboard, but no chime, no video. @techstep mentioned it does post every so often (chimes/video/blinking disk icon). When I tested it, I could not get it to post at all after 30 attempts.
Visual Inspection: caps were toast, they had leaked and there was cap goo around the caps and nearby chips. The leakage actual seems to have eaten the printed board labels (cap IDs, resistor IDs, etc).. those printed labels were falling off the board like water based decals.
Recap: I took off all the electrolytic caps, replaced all of them with equivalent tantalum caps, cleaned up the board as much as I could including gently cleaning the legs of the surrounding chips that had signs of corrosion and green gunk.
Post Recap Test: the problem persists BUT with a change. Whereas before I was not able to get the board to post at all, now I can get it to post more often than not. So more often than not, I get a chime, I get video, and I get a blinking disk icon. I also fully booted the motherboard with an external SCSI disk no problem.
Current Symptoms:
Given it works after the second or third time, and works after it's been successful, it seems like a capacitor somewhere? I had thought it might be temperature but it's not, because even on a cold boot, the second or third attempt works, before anything heats up.
Another possibility might be the power supply. It's the original power supply. I checked the various pins (5V, 12V, -12V) and those all check out and have proper voltage. But maybe there's some timing thing going on after the PSU's sat for a bit?
I know these 840AVs are notoriously hard to deal with once caps have leaked. So hoping to see if anyone has some additional suggestions on things to try before I return this to @techstep.
Setup: the motherboard, PRAM battery installed, memory installed, connected to speaker, connected to original power supply, connected to 13" Apple monitor, no drives attached.
Symptoms: push the power button, PSU fan spins up, voltage seems to be coming to the motherboard, but no chime, no video. @techstep mentioned it does post every so often (chimes/video/blinking disk icon). When I tested it, I could not get it to post at all after 30 attempts.
Visual Inspection: caps were toast, they had leaked and there was cap goo around the caps and nearby chips. The leakage actual seems to have eaten the printed board labels (cap IDs, resistor IDs, etc).. those printed labels were falling off the board like water based decals.
Recap: I took off all the electrolytic caps, replaced all of them with equivalent tantalum caps, cleaned up the board as much as I could including gently cleaning the legs of the surrounding chips that had signs of corrosion and green gunk.
Post Recap Test: the problem persists BUT with a change. Whereas before I was not able to get the board to post at all, now I can get it to post more often than not. So more often than not, I get a chime, I get video, and I get a blinking disk icon. I also fully booted the motherboard with an external SCSI disk no problem.
Current Symptoms:
- Machine is cold (has been powered off and disconnected for over an hour).
- Connect the power to the power supply and push the power button. Nothing.
- Wait a second, and push the power button again. Chimes, get video, get blinking disk about 50% of the time.
- If the second attempt didn't work, wait another few seconds, and push the power button again. Chimes, get video, get blinking disk about 75%+ of the time.
- Once I get the machine to post (ie. it chimed), it will ALWAYS chime if I restart or even power down the board but as long as I power it again within 10 minutes or so.
Given it works after the second or third time, and works after it's been successful, it seems like a capacitor somewhere? I had thought it might be temperature but it's not, because even on a cold boot, the second or third attempt works, before anything heats up.
Another possibility might be the power supply. It's the original power supply. I checked the various pins (5V, 12V, -12V) and those all check out and have proper voltage. But maybe there's some timing thing going on after the PSU's sat for a bit?
I know these 840AVs are notoriously hard to deal with once caps have leaked. So hoping to see if anyone has some additional suggestions on things to try before I return this to @techstep.