820-01598 no keyboard or trackpad

I got a 820-01598 that was liquid damaged around the trackpad connector and did not turn on. Trackpad connector was burned on PPVIN_S4_TPAD_FUSE. I cleaned the area and replaced the trackpad connector with a new one. All diode mode readings on the trackpad connector seemed to match a good board now, so I plugged the board in using another known good trackpad and it boots to the OS, but keyboard and trackpad do not work. I rechecked all diode mode values on the trackpad and keyboard connector and made sure there were no broken traces there. With the trackpad connected, I was not getting any voltage on TPAD_SPI_EN, which comes from the T2 chip. I removed U6855 and found I have OL on pin 1, which is not normal. Seems the trace between the T2 chip and pin 1 of U6855 is broken. I cannot run a wire without removing the T2 chip, which I do not want to do. Wondering if I can connect Pin 1 of U6855 to TPAD_3V3_SPI_INT_L, or some similar signal to make it work? Any ideas?
 

2informaticos

Administrator
Staff member
KB/TP work in USB mode, before loading macOS (boot menu)?

Keep out U6855 and bypass R6854 pads.
Let see if this tricks the T2.
 

2informaticos

Administrator
Staff member
TP SPI data lines don't go directly to T2.
But who knows, level shifters may got damaged and affected T2 too.

Maintain the bypass and try changing U6860.
 
I tried another trackpad from an A1708 because I was not sure if the trackpad I was testing with was actually good or not. With the A1708 trackpad, it works in the boot menu, but then does not work in the OS or recovery mode.
 

2informaticos

Administrator
Staff member
macOS accesses TP through SPI bus and you have missing the required enable signal.
Did you test maintaining R6854 bypass?
 
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