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[Solved] 820-00928 Refuses boot or 20V negotiation when power/touch button connected.

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down1nit

Member
Came in for no power, was at another shop, looks washed and not rinsed. No visible corrosion. Unknown if water damaged but likely given white chalky film around every solder joint and 100% pink moisture indicators.

Disassembled for initial test, gets 20V, draws boot amperage. partially reassembled, Left side fan stuck at 100% at S0 state : fixed, found missing Q6000 and destroyed trace, likely got knocked off by other shop. Fan seems perfect now.

Current problem: If i plug in the touch/power button the machine refuses to negotiate 20v. Verified all resistors around J4900, and pullups for data, voltage on pin 7 "menu_key_l" present at 3.3. No other voltage, like 1.8. Removed TouchID button, connector looks good, cable seems fine, kinda nervous going much further with the button assembly itself. Never responded to SMC reset so maybe it's screwed. I have a spare button at the shop i can get next week.

U4920 gets enable, gets 3.3. Does not output. No short.

I can probably send this off without power/touchid button working, but maybe someone has a clue?
 
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2informaticos

2informaticos

Administrator
Staff member
Changing power button assembly will stop touch ID to work.
SMC_ONOFF_L drops to 0V when pressing power button?
 
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down1nit

Member
Yeah, I don't have access to Apple's pairing device, so I told the customer touchID might be gone.

Tried another touchID button, it worked. I took the original button out, saw corrosion around the 4 contacts, set the hot air to 350 C and kept it there for about a minute, then removed the pressure switch from it's board on the back of the touch id, cleaned the contacts very carefully, and placed it back onto the touchID button. I don't know if it was the corrosion i could see, or if it was beneath the spot welds on the touchid sensor that benefited from a reflow and flux drench.

Haven't tried logging in to see if touchid still works but at this point I barely care. :)
 
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