Hello,
I recently refurbished a Quadra 900 PSU, it had bad capacitors, mostly due to bad storage, all electrolytes replaced with the proper part.
Previous recap with the same BOM when fine on a previous Quadra 950 but this just won't stay up.
At first the Quadra 900 wouldn't power on, I though I may not have properly press the power key, trying again few times, it powered up and then immediately shutdown. And then it stayed powered on but only for few seconds or minutes.
I managed to run a test via MacTest Pro, just before it powered off by itself again. All tests passed, motherboard is fine.
Power rails values are fine with almost perfect 5V and acceptable 12.4V, in range with specs.
I tested the 900 motherboard with my Quadra 950 PSU, and it worked fine and stayed powered without any problem, which confirm it's PSU related.
I tend to think the self-power circuit is not properly calibrated after the capacitor been replaced and it failed to self-maintain the power at some point.
There is at least 3 potentiometers in the PSU, 2 on a daughterboard IIRC, but I fail to find any information at schematics to nail this problem down.
Does anyone knows where I can find schematics or more detailed information about this PSU? I don't want to make an ATX conversion at this point.
EDIT: seems the 5V Trickle rail drops every time the PSU shuts down by itself, but stay stable when the power is manually turn off.
Waiting for my PSU to discharge before further inspection.
I recently refurbished a Quadra 900 PSU, it had bad capacitors, mostly due to bad storage, all electrolytes replaced with the proper part.
Previous recap with the same BOM when fine on a previous Quadra 950 but this just won't stay up.
At first the Quadra 900 wouldn't power on, I though I may not have properly press the power key, trying again few times, it powered up and then immediately shutdown. And then it stayed powered on but only for few seconds or minutes.
I managed to run a test via MacTest Pro, just before it powered off by itself again. All tests passed, motherboard is fine.
Power rails values are fine with almost perfect 5V and acceptable 12.4V, in range with specs.
I tested the 900 motherboard with my Quadra 950 PSU, and it worked fine and stayed powered without any problem, which confirm it's PSU related.
I tend to think the self-power circuit is not properly calibrated after the capacitor been replaced and it failed to self-maintain the power at some point.
There is at least 3 potentiometers in the PSU, 2 on a daughterboard IIRC, but I fail to find any information at schematics to nail this problem down.
Does anyone knows where I can find schematics or more detailed information about this PSU? I don't want to make an ATX conversion at this point.
EDIT: seems the 5V Trickle rail drops every time the PSU shuts down by itself, but stay stable when the power is manually turn off.
Waiting for my PSU to discharge before further inspection.
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