820-00239 dead. Missing 20v.

[joshAU]

Hello again.

I have a 820-00239 that appears dead - no life, no fans.
No USB activity at all.

No signs of any liquid anywhere on either size of the board.
Tried with known good AC adaptor with just the bare board.

I don't seem to get 20v anywhere - the most I get is 5.7 volts.

I'm also fairly unfamiliar with and very confused by the whole USBC 4x ports setup.

With the charger connected to USB TA (JB500 outer USBC port)
PP20V_USBC_TB_VBUS = 5.7V (measured at FB200)
The other ones TA, XA, XB all read 0.0v.

UB400 appears to be getting hot, but nothing else is.

Any advice greatly appreciated.

 

[2informaticos]

Remove UB400 and confirm short disappear from both rails.
Then solder new/good chip...

 

[joshAU]

Thanks again for your advice 2informaticos.
Unfortunately, that job went pear shaped.

What temperature do you need to remove UB400?
I ended up overheating the board, to the point that other components started floating....its game over unfortunately for this board.

I read that all 4 CD3215 chips have to be working for any to work... is this correct?
Anyway, lessons to be learnt, I guess.