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820-2914-B No keyboard and trackpad

Beto_MFC

Beto_MFC

New member
PP3V3_S4 is arriving with only 2.4v at R5704, right before U5701. Pulled off U5701, all caps, U5750, U5755 but still no getting 3.3v. PM_SLP_S5L is measuring 3.3v but I think what is biting me here is that I only have boardview for revision A of this board. P3V3_S4_EN is not present but i don't get it as it is made by PM_SLP_S5L which measured ok.
 
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dukefawks

Administrator
R7916 is marked as "no stuff" on the diagram, but is it really not on the board? I see no other way for P3V3_S4_EN to be connected...
 
Beto_MFC

Beto_MFC

New member
R7916 is not on the board. This schematic is clearly missing something. You think is ok to bridge R7916? May a board internal trace got burned and developed resistance, as PP3V3_S4 arrives with 2.4v at the keyboard and trackpad HUB?
 
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Beto_MFC

Beto_MFC

New member
Confirmed. Measured below 3.3v on SMC_S4_WAKESRC_EN too. As it is created by the SMC, can I assume it's a bad SMC case? If that is correct, woudn't be easier to make a bridge?
 
Beto_MFC

Beto_MFC

New member
Measuring resistance between SMC pin 10 probe point and U9480 I get something in the order of mega ohm. Concluded that the board trace got fucked, making a bridge between those 2 points then.
 
Beto_MFC

Beto_MFC

New member
After bridging I got 2,8v at the cap before U5701. Then removed U5701 and got 3,17v. Is that enough?
 
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dukefawks

Administrator
No that is no good of course. You removed all the load on that rail now that U5701 is gone. With the load of U5701 there should be 3.3V. Is enable now coming to Q7812? Is pin3 of Q7810 being pulled down?
Why of why did you pull off U5701, another variable now to the problems.
 
Beto_MFC

Beto_MFC

New member
dukefawks said:
No that is no good of course. You removed all the load on that rail now that U5701 is gone. With the load of U5701 there should be 3.3V. Is enable now coming to Q7812? Is pin3 of Q7810 being pulled down?
Why of why did you pull off U5701, another variable now to the problems.
Click to expand...

Removed becouse it was still measuring low. Measured resistance from SMC_S4_WAKESRC_EN to P3V3_S4_EN on C5701 and get 10k. Maybe another trace got burn? It feels like the schematics are incomplete on this one...
 
Beto_MFC

Beto_MFC

New member
With U5701:

Q7812 pin 2: 3.33v
Q7810 pin 3: 0v
U5701 PP3V3_S4_PSOC probe point: Voltage all around and never above 2.1v.
 
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dukefawks

Administrator
Voltage before(pin7,4) Q7810 and after(pin 1)? If the voltage drop is over Q7810 then measure resistance to GND on PP3V3_S4_PSOC
 
Beto_MFC

Beto_MFC

New member
Both pins on Q7810 measured 3,33v. Can we assume is the board inner connection that got burned? I'm just about to bridge it.
 
Beto_MFC

Beto_MFC

New member
I measured current draw with my power supply at PP3V3_S4_PSOC and it was 0.0024 amps. So no short on this line. Then I bridged it which bring keyboard back to live. But still no trackpad, which I swapped with a known good and still no dice. 3.3v arriving at keyboard connector. Safe to say it's time to replace U5701?
 
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dukefawks

Administrator
Issue is now between trackpad connector and U5701. Do a diode mode on all the connector pins and compare. But yeah U5701 is easily killed, that is why you never pull it unless 100% sure it's dead.
 
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