820-3332 Only boots in SMC Bypass

[BCConnection]

820-3332 board came to me water damaged. Previous company tried a repair was not successful.

U7000 area was badly damaged, replaced, made jumpers, and repaired the area Computer worked passed system checks, so I sent it out.

Month later computer comes back wont boot normally. SMC bypass it will boot.

Main power rails are there. Charger light changes green to orange as normal. Just will not boot from normal power button press.

Anyone have an idea of where I should look because Im lost as of right now.

3v42 present
PP BUSG3H present
3v3S5 present

 

[dukefawks]

Sense resistor issue, check R7021/22/51/52 and associated traces.

 

[BCConnection]

R7021 10.5 ohm
R7022 10.5 ohm
R7051 2.3 ohm
R7052 0 ohm

Had to rebuild traces for both of these lines when repairing U7000 area. Lines have continuity to U7000

 

[dukefawks]

Measure total resistance of sense circuit between pin 17/18 and 27/28.

 

[BCConnection]

17/'18 4.4 ohm
27/28 43 ohm

 

[BCConnection]

hmm thats changed... resistance changed on R7022

 

[BCConnection]

Replaced resistor still same symptoms

 

[BCConnection]

27/28 22 Ohm

 

[BCConnection]

Now u7000 is outputing 5V it was 12.4v after resistor swap. Tried to boot. No boot. Tried SMC bypass no boot.
Meter G3H getting 5v. I replaced U7000 when it first came back it was doing the same so I replaced it then. Now its doing the same thing again.

 

[dukefawks]

Nothing to go on for me. Something around U7000 is screwed up. The usual are R7005, R7021/22/51/52, badly soldered 6259.

 

[BCConnection]

Ill replace U7000 tomorrow again. Ill also pull some parts from another board and replace all the resistors see if anything changes

 

[larossmann]

If R7005 blows, 99% of the time, it's knockoff charger.

If R7021/R7022 blow, it is often a bad U7000. U7000 provides a path between the charger voltage and ground. Be careful how much heat you use on U7000 when soldering is my only guess here, and ask the customer to bring their charger so you can see if they are using a proper charger or some amazon garbage.

 

[BCConnection]

Charger is an Apple Mag Safe 2 original charger I have it here. I tested it with their charger and mine same results.

Retested this morning still putting out solid 5v on g3h. Ill replace U7000 again here in a few see if anything changes. Its just odd to me when G3H was 12.4v the computer still would only boot in SMC bypass.