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2informaticos, I have littarly just checked every single rail, non are short, all VCORE look good. The only rail short is PPBUS.

820-3330 board, customer states the were using the machine, heard a popping noise and smelled a burning odor. Board is not liquid damaged, and dont see any physical damage. PPBUS_G3H is dead short, when I inject votage the board heats up right around the corner of the CPU, but it really seems...

I replaced u8900, GPUVCORE is now restored, thanks fellas.

Yes, I have tested with the original screen, with my own known good screen, and measured vcore with no screen. is there a certain significance is there a certain significance to having a known good screen attached? Shouldn't GPUVCORE be present with or without a screen attached?

Board looks virgin to me Duke. If I understand this correctly u9100 will not produce the EN signal, if it does not see the GPU, is that correct?

Yes, the machine chimes.

820 3332 No GPUVCORE, touched up the pins leads @ u8900 twice, and reflowed the chip once. GPUVCORE_EN is also missing. No liquid damaged on board.

Not on this machine, did not know u8900 could cause a thud type of issuse, but i will definitely give it a shot.

3v42 is 3.39v with battery only. I should have mentioned that this is in internment issuse, but when it is occurring, yes, the machine shuts right down when magsafe is disconnected.

No liquid as far as I can tell, dont know of any drops, no major damage on casing

Yes, and gives charging lighting bolt when connected to magsafe

820 3332 runs off charger but not battery. Greenlight on MagSafe PP3V42 3.396v PPBUS G3H 12.68v running on MagSafe PPBUS G3H 10.78v running on batt PPBUS G3H 10.93v running on MagSafe and batt PPVBATT G3 CONN 10.76v SMC BC ACOK 3.25v CHGR ACIN 4.80v PP18V5 DCIN CONN R 20.15v PPBUS G3H R 12.67v...

I moved on.

Diode mode measurements for the following C8320 Pin 1 .287v Pin 2 OL L8300 .530v C8311 .530v I have continuity starting at both connector side and cable side. Also reflowed all connector pins to make sure I didn't have cold joint, no change.

Continuity from the pins to the end of the cable is good, fuck this board.

P RAM reset was tried a few times. I no missing components as far as I can see, and I'm definitely testing with a 2015 LCD. Will a cable from a 2012 retina machine work for testing?

Yes the 5v is only present for a few seconds, then drops to, and stays at 0v. Sorry maybe I wrote my original answer poorly.

Yes I'm sure, I checked with high power led flash light that I always use to check for back light, plus 0v on L8300

Yes confirmed correct 2015 known good working screen has been tested, still no display. This board looks clean as a whistle, as far as I know the display just randomly stopped working.

Pins 28-30 get 5.15v, Pin 5 gets .040v for a few seconds when the board starts, then drop to 0v.