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IIsi Sony PSU daughter board not working after recap
Posted by: elemenoh on 2020-05-31 03:24:58
After a full recap of the PSU and daughter board, the Mac won't power up. When I swapped the daughter board from another working (recapped) PSU it worked okay.

So something is bad on this board, but I'm not sure what. I gave it a couple of cleans and checked that all the pins make contact with their first several connection points.

Does something here look clearly bad? Where would be a good place to focus troubleshooting?

Before and after photos:

IIsi PSU Before Recap.jpeg

IIsi PSU After Recap.jpeg
Posted by: Fizzbinn on 2020-05-31 07:17:03
Have you tried scrapping as the traces to see if there is actually copper until the black spots? Maybe compare with the known good board?
Posted by: elemenoh on 2020-05-31 10:53:25
Not many areas flaked off. I think I've now checked every trace and did find one bad connection. Patched that but got the same symptom.

All the joints were reflowed anyway. Even with a lot of flux and scrubbing the pins on the IC don't look great, but test okay.

I guess I can try swapping parts from one board to the other but I've probably already sunk more time into this than it's worth. Any other suggestions?

IMG_2507.jpeg
Posted by: bibilit on 2020-05-31 15:11:41
The main IC is the main culprit usually. 

Reflowing is not enough. 

Removing the chip, cleaning underneath and soldering back is the way to go. 

Looking at the picture, the right side legs doesn’t look to be touching the board. 
Posted by: elemenoh on 2020-06-01 07:32:52
@bibilitThat did the trick! It's working great now. Thanks!
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