820-3476 CPU really hot when battery plugged in


This 3476 has had liquid damage and a couple of resistors replaced to get the I/O board USB to stop turning itself off. (Which is sorted)

I'm also getting issues when the battery is connected.
The CPU gets crazy hot even during ASD. Never gets a chance to load the OS.

I ran an air line over the heatsink just to keep it cool enough to get it to complete an ASD test with the battery attached.

its failing on IPBR - Charger - BMON test
Sensor above the high limit.

I've looked around the battery connector area but everything seems to test fine.


Could be corrosion around U7100, check resistance between pin 17-18 and between 27-28 from ISL, also check for corrosion around SMC....


CPU getting hot has nothing to do with BMON, so first sort that out. Is the heatsink conducting heat? Is the fan ramping up to max?


Thanks for the replies.. The heatsink is certainly conducting the heat and the fan isn't ramping up at all. It will ramp up during a fan test though.
If I start it with the battery unplugged, its fine and then if I plug it in while its on, the heat on the CPU shoots up within 5-7 seconds.


It's as if the CPU is being maxed out by something as it won't load anything when the battery is connected while its getting hot.


I ran ASD again but this time it passed :confused:

Its still getting really hot though and I have to blow extra air across the CPU and heatsink to get it to stay on. If I leave it to get really hot, it artefacts on the screen and crashes. But the fan still doesn't kick up.

U6100 wasn't ever touched but I'll take another look around it today and make sure the resistors are reading good.