You’ve got a ton of corrosion on UD13. I am betting there is a lot of cap too under there too. You’ll need to check continuity to all of the points suggested by the soft power schematic. Those chips are all still available and I would replace them but ultimately they may need to be cleaned underneath.I know stuff is shorted. But, the second UE13 is fine. +5v goes to +5v, ground goes to ground, everything is isolated. But the first UE13 and the HC74A (UB13) appear to be shorted. I'm using the circuit diagram from another thread, attached below. The red circles show all those pins tied to ground, but they shouldn't be, should they? UB13 pins 10 and 13 should be +5v, with 11 & 12 on ground. But all of them are connected. The first UE13 (just above UB13), pins 1 & 14 are tied to ground. They should be +5v.
How likely that it might be one of these chips? I don't have a heat gun or chip quick, this is going to be tough to remove if I have to go that route.
Anyone have any ideas?
I found the power circuit schematic you referenced to be fully accurate when I fixed my IIci. There were about three jumper wires I had to add. Note that pin 1 might between the chip and Apples markings on the logic board (I think and I can’t recall which defence is used by the schematic)Sigh. While there was a ton of crap under those ICs, after removing them, the short is still there.
I've about exhausted my ability to diagnose this board. Unless someone else has any ideas. I need to source another IIci board.