820-00850 MacBook Pro without Touch Bar functionality

[sekidata]

This 2018 A1989 board looks completely undamaged. It appears fully functional except that the Touch Bar neither illuminates nor registers touch. I tried connecting a known-good spare Touch Bar and nothing. Any pointers for how to troubleshoot this?

 

[2informaticos]

So machine boots correctly into macOS, no critical update error reported?

Did you check any voltage and signal on touchbar connectors?

 

[sekidata]

Machine fully boots, no errors. So far I have checked the 1.8, 3.3, and 5V rails for the Touch Bar connectors and they are all there.

 

[2informaticos]

Check J5100 signals; pins 1, 2, 13, 15, 18.
Compare with good board, if possible.

You can also check J5110; pins 10 & 12.

 

[sekidata]

I haven't compared to a good board, but here are the signals (with connected Touch Bar):

J5100
pin 1: 1.8 (0V with Touch Bar disconnected)
pin 2: 0V
pin 13: 1.8
pin 15: 0.5 (0V with Touch Bar disconnected)
pin 18: 1.8 (0V with Touch Bar disconnected)

J5110
pin 10: 0V
pin 12: 1.8

 

[2informaticos]

Not sure about DFR_TOUCH_CLK32K_RESET_L and DFR_DISP_INT.
You should compare with other board; even not the same model.

 

[sekidata]

The only other Touch Bar board I have right now is activation locked and I can't get the bar to turn on. Will check back in when I have good board comparison measurements.

 

[2informaticos]

What said the client about how failure appeared?

 

[sekidata]

Actually, I just found the culprit: there was a mechanical issue with J5100, preventing contact on some pins. Touch Bar is fully functional now. That was a weird one.