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Nothing. I put back the BIOS chip from my donor board to see what happens and I got no drop in voltage on cpu vcore or signs of trying to POST. it could be a BIOS issue after all as original spill was around that area. Will order in another and pray

Had a look around U7400 and cant find anything else that looks bad. I removed R7550 and get voltage to pin 1 (think it was around 1V) as soon as I replace R7550 I get 0V on Pins 3, 4, and 5 on Q7550 and 0V on PPVCORE_S0_AXG. Dead CPU?

I get a beep when no RAM installed. I'll go back to U7400 and check all the resistors. I swear this board is a rite of passage from the repair gods to test my patience

When the DVD drive does it's auto eject thing PPVCORE_S0_CPU goes down from 1.118V to 0.919V

Yes - plugged everything back in and I get a solid sleep light on the front, DVD drive does it's auto eject thing like it's about to POST and then nothing. No video ouput on display and 0.001V on PPVCORE_S0_AXG

Quick update. I replaced U7400, R7402, R7403, Q7510, Q7520 and Q7550 and I now get 1.118V on PPVCORE_S0_CPU but get 0V on PPVCORE_S0_AXG. Any ideas of what to check next? I read in another forum that BIOS can cause this so I replaced the BIOS chip again but still no luck. Thanks so much...

OK new issue: machine turns on but I get no video output. I have no voltage on PVCORE_S0_CPU and PVCORE_S0_AXG. All other main voltage rails appear to be present. I get a reverse diode reading on both of these CPU rails of 0.002V with U7400 removed. Is this a normal diode reading or does it...

Have done I think I have a U7400 problem as a few burnt probe points around those. Will check further and get back to you

Replaced RTC Chip U2600 and I get an S0 state and the fan is spinning! No video output or chime though - will keep investigating but at least that's one problem solved! Thanks

Nothing at all on PP5V_S3_REG. Replaced BIOS - no change. Have given up on this one for now thanks for the help anyway.

Sorry PCH! I'm new this this when it comes to the advanced hit your head against a wall stuff. Tried reflowing the SMC with flux to get rid of any crap under the chip but didn't change anything nothing really corroded around the area. As far as I can diagnose it will not go into an S3 state...

Water Damage on top of board around EFI chip, SMC and thunderbolt chip and similar area on the other side of the board. RTC resistor values: R1800: 3.332V pin 1 3.236V pin 2 R1801: 3.332V pin 1 3.057 pin 2 R1802: 3.332V pin 1 3.327 pin 2 R1803: 3.332V pin 1 3.327 pin 2 R1800: 325K R1801: 1M...

Hello, I have an issue with an 820-3115-B board. Board was liquid damaged - put it through the ultrasonic cleaner and powered it up - green light and fan spinning. Great! Disconnected magsafe and went to have something to eat. Came back 10 minutes later will not power on: gets green light but...