820-00138 turns on, battery error symbol, then turns off. Works fine in SMC bypass

2informaticos

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Post voltage for pins 9, 15, 26 of U7100 and F7140/41.
Also post exact value (measured onboard, ohm scale) for R7180/81 and R7185/86.
Check resistance between pins 17/18 and 27/28 (ohm scale) at U7100 too.
 
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kevinklinkmuller

New member
U7100
pin 9 - 0.030v
pin 15 - 0.065v

As i was measuring this, the R7020 blew up. I think i might've plugged in the charger wrong because there's no green light. have replaced it with another resister with the same marking "470" but still no green light. What did i do :(
 

2informaticos

Administrator
Staff member
R7020 usually gets burnt because of short in U7090, or one of the filter caps from its pin 6.
Seems to be U7090 in this case.
Also check for short, or low value at 3V42 rail; before and after U7090 is removed.
 

kevinklinkmuller

New member
before and after removal the 3v42 rails are quite low. 10 ohms short to ground, so must be a cap, should i inject voltage and see what heats?
 

2informaticos

Administrator
Staff member
I don't think that.
Something else happened there.
Unless you used fake charger, which gives full voltage always.
Original Apple Magsafe 2 gives only 3V at the first moment, before the board is detected correctly.
Bench power supply also can generate such kind of problem.
 
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2informaticos

Administrator
Staff member
Every day can learn a lesson; but sometime can be pricely...
Next time when you use bench power supply, set it at 3V and go high to nominal voltage after Magsafe is correctly connected.
 

2informaticos

Administrator
Staff member
At least at the last point before the "tsunami"
Or even better, in case if SMC was the culprit; which I doubt...
 

2informaticos

Administrator
Staff member
Did you get it from same model donor board?
Machine should start in SMC bypass, as before.
Something went wrong in the process, or SMC is bad/incorrect.
Also check SMC_AVREF voltage.
 

kevinklinkmuller

New member
Actually, it wasn't from the same model donor. the chip has the same markings. I guess you're going to tell me now that the programming is different hahaha

I can't find SMC_AVREF in the schematic or board view
 

2informaticos

Administrator
Staff member
"I can't find SMC_AVREF"
PP3V3_S5_AVREF_SMC to be more specific.

"I guess you're going to tell me now that the programming is different"
Exactly!!!
 

kevinklinkmuller

New member
Hi there! Revisiting this today. Bought donor board and have reablled SMC from a 820-00138-a board but I noticed the board i'm repairing is 820-00138-05

have tested that SMC and while I get the orange / green light and while the light turns screen when i try SMC bypass, it's not doing anything more than that :(

Will these SMC's work?
 
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