A1708 820-00875 won't power on; 20V 500mA initially, then 0A.

[ipmungam]

Our 2016 13" mbp has had some issues since liquid got into one of the USB-C ports a few years ago, but it was working well with the latest (aftermarket) battery for several weeks -- until now.

With the board out and no battery, it negotiates 20V properly and starts to take 300-600mA (let's call this phase 1). With the screen attached it will even show the red low battery icon. Then after 5-10s the current drops to near zero and nothing more happens (phase 2). Power button has no effect.

I have checked all the coils I can see while unpowered and none seem shorted to ground. PPBUS_G3H is 13V during both phase 1 and 2; the other power rails seem to power on during phase 1 (I only have a few seconds to check, so can't be sure, but the display briefly works so must be something right). However most everything other than PPBUS_G3H goes to exactly 0V in phase 2. It's as though they're being shut down.

Any thoughts most welcome.

[mon2]

Flux and remove F7000. Power up again. What is the voltage to ground on the removed fuse pcb pad # 1 ? Is it stable or still power cycling?

[ipmungam]

Thanks very much for the speedy reply -- I will try this and report back.

[ipmungam]

Hello again. Took some work but I got F7000 off -- now the board negotiates 20V but never takes more than 20mA, which I suppose makes sense.
The voltage at the F7000 pin is a steady 13V. This is consistent with when the fuse was in -- it wasn't power cycling so much as it seemed to start the pre-boot process (phase 1), but then got interrupted at some step and shut down the rest of the power rails.

[ipmungam]

I've tested resistance to ground for all the power rails I can see listed in the schematic -- no shorts as far as I can tell.
This suggests I'm missing an enable signal somewhere -- any suggestions on where to start looking would be welcome.

[mon2]

Do you see the same low battery graphic with and without the battery attached? Can you test with another known good battery? Amazon?

[ipmungam]

Thanks. With F7000 removed I have reinstalled the board with the "new" battery (recently bought on Amazon and worked for 1-2 weeks) and "old" battery (bought aftermarket a few years ago, swollen cell). [I don't have the "original" battery anymore.]

0. No battery: 20V, draws 0-40mA, no longer seeing the low battery screen (to see an image does F7000 need to be in place?).
1. New battery: 5V, power cycles every time it tries to reach 20V.
2. Old battery: 20V, draws 0-40mA, no screen.

[mon2]

Yes. Add fuse. Test again and confirm the graphics.