Another 820-01700 - A2141 with 5v 0A

[cstout]

How might I test the high side mosfet to confirm that it has indeed failed and destroyed the board?

[cstout]

mon2 Do you have any final suggestions for this bad boy or should I call it quits? I truly appreciate all your help. It's been a great learning experience.

[mon2]

I think it is a 'dead horse' but you can confirm the same by applying a voltage onto the removed downstream fuse pad @ 0v8 or even 1v0. Then check who is heating up. It should be anyone with the 0hm or similar low resistance to ground. Respectively, that same leg was most likely hit by the original highvoltage feeding the high side mosfets that are often present on the buck converters,

Some buck converters have internal high side and low side mosfets; while others have these parts external. The devices with the external mosfets do so to support higher peak currents - like the CPU / GPU power rails.

[guruji]

please check the ssd power section this board has only the ssd getting short check the impedance of the inductors of the ssd supply.

[reformatt]

The only time this ends well with SSD power rails is if you have a shorted cap on the 2.5V rails (which is very common due to the fans sucking in dust etc over the both sides of the board). If however that short is also transposed to PPBUS_G3H, then it's usually game over. A shorted 2.5V SSD regulator will fry the NAND's.

Additionally, these machines have the CPU/GPU MOSFETS at the upper side of the board, and boost components for each DRMOS correspondingly close as well. You only need a very small amount of corrosion here from liquid etc to have catastrophic failure due to changes in the boost circuits. Last week I had a very small amount of liquid damage to U7230/R7239/C7239 on a 820-1700 board with U7230 shorted (and dead CPU as a result). The rest of the board was clean but that's all it took.

Apple used to some protection in these areas on the older models but there is nothing there now. For such an expensive machine there are lots of booby traps.

[guruji]

You right. This is the worst machine they have built as there is always corrosion on the ssd side so the dust accumulates that area and 90% of the time takes away the ssd and what makes it worse is they have glued the ssd with epoxy.