820-3476A Short to ground on PPVCC_S0 HELP

PowerUP

New member
So I had a customer bring in his device with water damage. Very clean. NO chime, No backlight. Only real corrosion was on R3201 on the PP3V3RHV pad which was entirely gone. I ran a Jumper from the thunderbolt connector pad, to the replacement resistor and tied it all back in. But I can not for the life of me find where this thing is shorting to ground on the PPVCC rail. I put 1.5v to the rail but nothing got hot. (not sure anything will at that low voltage.) Am I just stupid and don't know how a multimeter works?
 

aprendiz

Moderator
this is not a short..... Do the basics, PPBUS_G3H, green/orange light, fan spin?? PPVCC_S0_CPU is coming high??
 

PowerUP

New member
apologies, I normally work on phones. I get orange/green light on charger, and fan spins up. no chime, no image/backlight. when i put my multimeter in continuity, positive on PPVCC_S0_cpu, neg on ground, i get a beep.
 

aprendiz

Moderator
Dont do that when power is applied to Logic Board, you will kill your multimeter........ What is the voltage on PPVCC_S0_CPU?? if you connect a pendrive with a led on it, does it light up?? can you do a PRAM reset?? Caps lock works???
 

PowerUP

New member
i've tried the PRAM reset with no effect. I know not to put continuity with power to a board.. I checked with the device dissembled. No caps lock light. 36 mV on PPVCC_S0-CPU
 

PowerUP

New member
All other rails are present. This one is the only one I get tone to ground in continuity mode. This is a very different world from cell phones. Two rails is all I'm used to so please forgive my ignorance. I have good voltage on all the other rails when i plug it in to the charger. There was corrosion around the JTAG connector and the KB backlight connector. I removed both and re-tinned he pads and reinstalled the connectors. Fan spins up and I have Orange light on the magsafe and no caps lock light.
 

dukefawks

Administrator
Check around U6100 and the termination resistors in series with it. Resistors and traces are a prime suspect, check continuity between them all and resistor values.
 

PowerUP

New member
OK, so I checked all the resistors around u6100, all good. I then reheated u6100 for good measure as I didnt have donor board for it. I got backlight and chime but no display. I did a NVRAM reset and now im back to no backlight, no chime. frustrated
 

PowerUP

New member
can J6100 be removed and still boot the device? I did not remove the chip. No visible corrosion around u1900
 

TCRScircuit

Super Moderator
Staff member
J6100 is a JTAG connector... Remove it, you do not need it. THIS IS DIFFERENT FROM THE CHIP YOUR THINKING OF! I believe you were thinking of u6100.
 
Top