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iix-no-power-bodge

Juror22

Well-known member
I haven't seen where there is a format for bringing back pages that are missing.
I found this on the internet archive and found it useful before and hope others will again.
Although I did not originally post (or even contribute to) this thread, there was some useful information that I would like to resurrect, so here goes.

elemenoh said:
“This IIx logic board was not working after recap. I repaired a couple of obvious broken traces, but had trouble finding whatever was causing no signal to the PSU sense pin. I read a common problem is a break between R3 and R19, but it wasn't clear what side of either needed to be wired to the other. For others that might need a reference, here's the bodge that worked for me.” (image not available)

Verault said:
“Hah! I had the exact same problem on a IIx board yesterday! I recapped the board and fixed two bad traces and no matter what the sense pin would not get the 5+ volts when the power button was pushed. It would start and boot fine when jumpstarting the psu. Anyway i saw one trave in particular that ran the length of the board that looked dark and foul. I did a continuity check on it and it was so badly corroded( strange thing is the traces next to it were fine) i found over 12 breaks in the trace making it so hard to follow. It running under all the simm slots was a pain as well but after a couple hours i found the other end and bodged it. Funny seeing your post the next day with the same troublesome trace.”

mg.man said:
“I too had the exact same issue on both a II & IIx 'board I restored last year. I used Doug Brown's resource”
https://www.downtowndougbrown.com/2015/03/explanation-of-the-macintosh-iiiix-power-onoff-circuit/
“I’ve seen other reports of this as well... I wonder if this thread can be made ‘sticky’?”
 
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