[SOLVED]820-3115 short on PPDDR_S3_REG

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XooP

New member
Getting really frustrated by this board and I need someone smarter than me to explain what is going on.
When I got the board it was water damaged but started with RAM beeping.

I found that there was no PPDDR_S3_REG voltage, and there was a short on the rail.

I have now replaced every capacitor around Q7330 and Q7335.

When I take of Q7335 the short to ground is gone. I have replaced Q7335 four times now :(

The short is worse when the board is warm, 0,010V in diode mode and slowly gets to around 0,100V when somewhat cooled.
When I take Q7335 off the board it immediately measures 0,370V

The donor boards measures 0,370V before I take the Q7335 off.

If anyone have any idea what's going on here please tell me.
 

dukefawks

Administrator
You are measuring on a scrap board without CPU I bet. Working board has 0,150 on diode mode when cold. Pin 16 and 17 on U7300 high? I bet just a dead U7300 if the enables are present.
 

XooP

New member
The boards all have CPUs, so 0,150 is okey? I have replaced U7300 as well. But now the board won't start anymore
 

XooP

New member
To answer you question, I do get 3.12 on pin 16, an 0V on pin 17. I now need to figure out why it won't start anymore
 

XooP

New member
Yes, I know. I'm stuck on this one. If I try to start it in SMC bypass its starts but with no CPU PPVCore. I do however get 1.5V on PPDDR_S3_REG when it starts.
 

dukefawks

Administrator
It had 3 beeps when you started so CPU Vcore must have been present. PPBUS at 12.26 indicates at least an SMC problem too, unless in SMC bypass of course
 

XooP

New member
Yes I know :) I don't understand why I don't have CPU Vcore anymore, I am considering swapping the SMC, but I thought I should address the CPU Vcore issue first.
 

dukefawks

Administrator
Could be anything. R7402 is common, besides that it can be anything that prevents the CPU from setting the voltage by talking to U7400. PPBUS still at 12.26 and green light is ok?
 

XooP

New member
This is going to the donor pile, I replaced the SMC and got 12.56V on PPBUS_G3H for about a minute and one of the battery SDA lines were 8.4V before it disappeared and PPBUS_G3H went down again to 12.26V :(. There must be some serious issues with this board.
 
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