820-00850 No 20V

[brunomotter]

Hello! Got this one from another shop here and it was missing U3100. I placed it again and had to run a little jumper to establish connection between R3109 and PIN 37 of U3100. Board pulls 5V and 0.25A from charger but won't negotiate 20V. I have 12.24V on PPBUS_G3H and T2 gets a little warm. Machine enters DFU, but does not complete restore or revive. Couldn't find any shorts on the board. I inspected the board and couldn't find any other missing components. I get voltage on all coils around U7800. Any ideas?

 

[2informaticos]

All USB-C ports have exact same behavior?

What error do you get in DFU mode?

 

[brunomotter]

UB300 was getting 5V 0A, replaced it and got 20V back. Board tries to start but I have no VCORE. DFU completed now, but still no VCORE. I have 0V on L7210/20/7410/20/30

 

[2informaticos]

All other voltages come on (big coils)?

Compare diode mode readings with good board.

 

[brunomotter]

All voltages present except those I told and L7702 and LB700 which are getting 0V. Don't have a good board of same model to compare diode readings.

 

[2informaticos]

Possibly bad CPU, or PCH.
Unless you find knocked off component, or broken trace on their areas.

 

[brunomotter]

Ok, another one to the pile of trash then. Thx!

 

[2informaticos]

Some workshops, intentionally remove/damage something when they can't fix a machine.
You should be aware of that...

 

[brunomotter]

Yes, I'm aware of that. Unfortunately for the costumer, only a replacement board will solve this now.