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8100 power on / off

imactheknife

imactheknife

68000
Ok, should have looked up 8100 before I bought this logic board. Was loaded with ram etc. it is now recapped but when power button is pressed it turns on then right back off. Psu is from my 8500 and is known to be good. I applied new thermal paste as well. Any ideas besides the 8100 being a pain in the arse?
 

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imactheknife said:
Ok, should have looked up 8100 before I bought this logic board. Was loaded with ram etc. it is now recapped but when power button is pressed it turns on then right back off. Psu is from my 8500 and is known to be good. I applied new thermal paste as well. Any ideas besides the 8100 being a pain in the arse?
Click to expand...
It probably won't be your issue, but Apple says do not run an 8100 (or 7100) without something plugged into the PDS slot.

They're also old enough that some need recapping. (Not all of them yet, I haven't recapped my 8100/100).

Edit - I see you have recapped, sorry, didn't pay attention.
 
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My 8100 board would chime with an empty PDS.

How soon is "right back off"? A couple seconds? A second? Half a second? Just a twitch of the fan?
 
Phipli said:
What happens if you keep the power button held down for, say, ten seconds. Does the fan still stop? Or does it go until after you release.
Click to expand...
I think it stays going but will have to try again to see. Have it off to the side for other projects. Will try later tonight hopefully
 
imactheknife said:
I think it stays going but will have to try again to see. Have it off to the side for other projects. Will try later tonight hopefully
Click to expand...
Sounds like it isn't latching, likely a broken trace, could be a dry solder joint, possibly a bad chip, but it usually isn't. There is a description of how the soft power works on older macs here :

restoring a battery-bombed IIcx

How much alcohol does that require? (Consults slide rule...) I think it would need more than a whole 16 ounce bottle to fill a tub to a depth of a few mm for submersion. A lot :) I try to recycle the alcohol as much as I can. Got used to recycling for 3d resin printing. I keep my general...
68kmla.org 68kmla.org

You probably won't need it, in fact I'd say it is more distracting than useful as you're probably just looking for a crusty trace near the battery, U46 or possibly U52, but find attached 8100/110 schematics. Page 16 is of interest.
 

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I know it is an old thread, but can you test the 8500 PSU in a PowerMac 8500?

I am testing some 8500 power supplies that were known good, and I only own a 8100.
The behavior is the same, if you press the power button it turns on for a second, then turns off. But if I use a proper 8100 power supply, it stays running.

I've read some posts that you can use a 8500 PSU in a 8100, but not vice versa.
Also on my 8100 PSU, if I pull the PS_ON pin high for a second to 5VSB, it latches on and keeps running. If I pull the PS_ON pin low (to ground), it will turn off.

On my both 8500 PSUs, it runs as long the PS_ON pin is being pulled high to 5VSB, but turns off immediately when I disconnect it.
 
mitchW said:
I know it is an old thread, but can you test the 8500 PSU in a PowerMac 8500?

I am testing some 8500 power supplies that were known good, and I only own a 8100.
The behavior is the same, if you press the power button it turns on for a second, then turns off. But if I use a proper 8100 power supply, it stays running.

I've read some posts that you can use a 8500 PSU in a 8100, but not vice versa.
Also on my 8100 PSU, if I pull the PS_ON pin high for a second to 5VSB, it latches on and keeps running. If I pull the PS_ON pin low (to ground), it will turn off.

On my both 8500 PSUs, it runs as long the PS_ON pin is being pulled high to 5VSB, but turns off immediately when I disconnect it.
Click to expand...
I’ve used a 9500 PSU with my 8100 and it works. So i imagine an 8500 which is quite similar should work too.
 
What is the part number and manufacturer of that PSU?
I am stumped as two PSUs (with same P/N) exhibit the same behavior...
 
mitchW said:
What is the part number and manufacturer of that PSU?
I am stumped as two PSUs (with same P/N) exhibit the same behavior...
Click to expand...
Yes my 9500 and 8500 psu work on an 8100 board and even my 840av. The extra molex connection just isnt used. So yeah, an 8100 psu wont work on a 9500/8500 because it isnt powerful enough and doenst have the extra molex connector
 
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