820-01700 2019 A2141, right shift key, left option, control, and caps lock led not working

liquid spill, both usb-c ports were stained with cranberry juice, and replacing both revived the MacBook. Works 100% other than these key problems. I haven't dived into the caps lock led yet. Just the three keys that don't work. I'm focusing right now on U6703 for these three. There's 3.3v coming in on pin 10. Pins 1-3 KBD_RIGHT_SHIFT_KEY, KBD_LEFT_OPTION_KEY, KBD_CONTROL_KEY all have zero volts. Pins 7-9 each has 1.8v. Pin 4 has 1.8, and pin 6 has zero volts. On a whim I replaced U6703 and same results. What's the distinction between KBD_RIGHT_SHIFT_KEY and KBD_RIGHT_SHIFT_L ?
 

2informaticos

Administrator
Staff member
Please, read how to properly check diode mode:
 
0001(6)5.jpg
the kb connector is just reverse of this, that area is in perfect condition. I found another U6703 and re-soldered it. The input pin diode measurements are all .482-.485v. However, I do not get any voltage on the corresponding pins of the keyboard connector. DZ6701 is still removed
 
by the way, those two bare areas bottom left of the pads are copper trace, I scraped them just enough to see a little shine-- **and there is continuity between pin 4 and the resistor it leads to**
 
so I re-soldered DZ6701, and checked the kb connector pins and still 0. I found another DZ6701 and soldered it and still 0v for the three inputs on the kb connector. I get 1.8v still on U6703 pins 7-9, and basically still 0 on pins 1-3.
 
contacts look clean
I compared U6703 voltages on a board from a working system and found that pin 6 should have 3.3v but our board in question is almost zero. this must be significant, yes?
 

2informaticos

Administrator
Staff member
Yes, reset output should be high.
That's the reason I suspected U6703.
Just in case, check R6752 and R8014.

On the other board, all 3 inputs have 0V?
 
yes all three inputs on the board from the working system are also 0V. after my last message I checked out R6752 and it was low and it basically broke off while I was testing, so I replaced it and now 3.3V on pin 6 reset output of U6703. Also R8014 now has 3.3V on both pins. but still no voltage on the kb connector.
 
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