820-01041 No power - PPBUS_G3H Shorted

[DaveDD]

Hi all!
Customer report sudden shut off while working.
No signs of spills and no damage.
It draws 5v - 0,02A from all USB ports.
Found pure short of PPBUS_G3H (0.000 on diode mode, 0ohm).
As you told me in an old case is safe to inject voltage to find the issue since is pure short , right?

 

[2informaticos]

Not right!

I hope you've checked for short disconnecting battery data cable first.
In fact, allow 10-20s after power is disconnected, before checking diode mode, or resistance on the MLB.

Compare short value (ohm scale) with the readings on the coils near the CPU & GPU.

 

[DaveDD]

On big coils I have 1,5ohm (with small differences between them).
pure 0,000 - 0,001 short on F7001.

 

[2informaticos]

If you are sure the short doesn't come from a secondary coil, then is safe to inject voltage.
Just in case, check the other big coils too (on entire MLB).

Remember, start with 1V and slowly increase (if needed).
Use tick cables and set PSU amp limit to max first.

 

[DaveDD]

C6455 was bad. Get warm injecting 1v in PPBUS_G3H line.
Replaced and everything works like a charm.
Thank you.