A2159 - liquid damage, no power - repaired liquid damage, no power but no video/tb

[tawnytim]

A2159 came in for no power, liquid damage(see attached image). I cleaned the corrosion from those two locations, and noted that the USBC pins on the power board were burnt from the event, so I replaced that board. Machine now draws reasonable current, running at 20v properly. I have a hot CPU, cooling fans, everything. Startup chime sounds, caps lock working so I think the device is booted into the OS, but I have no touch bar operation(is completely black) and no video on the LCD panel, and no video output via USBc>>hdmi.

Where might I go on from here?

 

[2informaticos]

Possibly something else affected by liquid.
External video is controlled through U2800 (TBT); may have accumulated crap underneath.

Do you get 3V3/5V_S0SW_LCD?
Also check power rails of J5100/10.

 

[tawnytim]

I have 3V3/5V_S0SW_LCD. I do not have power on J5100/10.

 

[2informaticos]

Did you try known good LCD assembly?

 

[tawnytim]

This is a A2159. Will an LCD panel from a A2338 work? I have one of those I can test with.

 

[2informaticos]

Don't do that mystake!
Especially in reverse way; an Intel screen assembly usually kills the M1 CPU.

 

[tawnytim]

OK, that's why I asked haha. ok, I'll just buy a screen for testing.

 

[tawnytim]

OK, a display from Mobile Sentrix, but still not working. I may be on to something though... this is right where the damage was - see image.
I also have 12v on C8401p1, but no voltage on c8410p1

 

[2informaticos]

Then rebuild the broken trace; use bypass wire.

 

[tawnytim]

I saw it lol.

 

[tawnytim]

Trace repaired. I now have .135v on C8411p1. Should I have 12v there with power connected but screen disconnected?

 

[2informaticos]

No; screen must be connected, to enable backlight circuit.

 

[tawnytim]

That's got it working. Thanks!