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820-00239 (A1706) No Keyboard or Trackpad

KootenayMacGuy

KootenayMacGuy

Member
Hi there. I just replaced the display on an A1706 (2016 13" Touchbar) and after installation, the machine would not boot up fully (20V @ 200-400mA, no image, no chime) Inspection using thermal camera indicated U7600 was getting hot. I proceeded to remove the board and test. I connected power and the unit booted up, and u7600 remained normal temp. I then connected a display and got a boot screen. I then reinstalled the board and connected all cables. The machine booted up, yet there is no trackpad or keyboard. Keyboard backlight is functional, so is touchbar. I measured voltages to trackpad and they seemed normal:

PP5V_S4=5.1V
SMBUS_SMC_3_SDA=3.4V
PP3V3_S4_TPAD=3.4V

If I disconnect the trackpad before booting the fans spin up full blast indicating that its not seeing a trackpad. Reconnecting and fans stay off as normal. I have tried three different trackpads, two different cables, and one other known good top case/keyboard...and still no function. Its definitely a board issue.

Where do I go from here?
 
2informaticos

2informaticos

Administrator
Staff member
"SMC_LID is 0.04V"
That is the problem.
Check its level disconnecting trackpad first.
If still low, check R5171.
Next, check HALL_SENSOR_LEFT/RIGHT levels.
 
KootenayMacGuy

KootenayMacGuy

Member
There is no change to SMC_LID when trackpad is connected/disconnected. Hall sensor left and right are both 3.42V with the lid open. When I tested R5171 the measurements were all over the place, so I replaced the resistor..but still got the same readings.
 
KootenayMacGuy

KootenayMacGuy

Member
Measured resistors around U5225 and R5320 was out of spec so I replaced it. No change.

I then found 136ohms of resistance to ground on SMC_LID. Found 2 ohm short to ground on Q4400 so I replaced it along with R4491 and C4490. That did the trick. Trackpad now working.

Thanks a bunch.
 
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