820-3115 left shift, control, option not working

[djdblaster]

These three keys are not working. Keyboard connector looks good. PP3V42 is present. When keys are pressed, they go high to 3.42V.

Any ideas?

 

[2informaticos]

Check around U5750...

 

[djdblaster]

What should I be looking there exactly?

PP3V3_S4 is 3.3V
SMC_TPAD_RST_L is 3.45V
PP3V42_G3H is 3.45V.

 

[djdblaster]

For example, when I press Option key, U5701 pin 56 goes high to 3.42V.

 

[2informaticos]

The 3 keys pass through U5750, before U5701.
You cannot make SMC reset, or none of them works independent?

 

[djdblaster]

Yes, the keys pass through U5750 before reaching U5701.
You mean PRAM reset? I did SMC by removing battery and power and holding power button for 10 seconds.

 

[2informaticos]

The combination of these 3 keys makes SMC manual reset.
My question, you cannot do that, or none of the keys works independently?
What is your ptoblem exactly?

 

[djdblaster]

I cannot do that and none of the keys work independently.

 

[2informaticos]

Right Alt, Option keys work?
The rest of keyboard is all OK?

 

[djdblaster]

Correct. They both work and rest of the keyboard works.

 

[2informaticos]

Then change U5750.

 

[djdblaster]

Even though it has correct values as well as when keys are pressed?

 

[djdblaster]

I've changed U5750, no luck. Even reflowed the old one with flux in case it had some crap under it.

 

[djdblaster]

I've also changed U5701 and J5713, no luck.

I understand if one of those three keys are not working, meaning bad trace or something else, but all three of them not working, even after changing the three components mentioned. Plus, signals are present and I tested a good known keyboard.

 

[2informaticos]

Post voltage at U5701 pins.

 

[djdblaster]

Measurements taken without the keyboard connected. I feel like I'll need to redo it with the keyboard connected, right?

Diode Voltage
01 0.406 0.000
02 0.646 3.300
03 0.651 0.000
04 0.640 3.300
05 0.635 0.000
06 0.655 0.000
07 0.429 0.070
08 0.598 0.060
09 0.514 0.040
10 0.591 0.050
11 0.638 0.010
12 0.626 3.300
13 0.637 3.300
14 0.642 3.300
15 0.654 0.050
16 0.657 0.050
17 0.653 0.050
18 0.660 0.050
19 0.000 0.000
20 0.623 3.000
21 0.634 0.010
22 0.339 3.300
23 0.663 0.090
24 0.667 0.000
25 0.656 0.090
26 0.657 3.200
27 0.654 3.200
28 0.657 3.250
29 0.656 3.260
30 0.656 3.260
31 0.656 3.260
32 0.657 3.200
33 0.540 3.200
34 0.656 3.200
35 0.654 3.200
36 0.656 3.170
37 0.654 3.200
38 0.656 3.200
39 0.655 3.200
40 0.657 0.000
41 0.658 0.510
42 0.657 3.200
43 0.649 3.200
44 0.658 3.200
45 0.649 1.170
46 0.655 1.180
47 0.651 1.170
48 0.657 1.170
49 0.338 3.300
50 0.000 0.000
51 0.550 3.280
52 0.620 3.300
53 0.560 0.000
54 0.651 0.700
55 0.404 0.000
56 0.405 0.000
57 0.000 0.000

 

[2informaticos]

Sorry, need U5750 voltages.
However, we take a look to U5701 values...

 

[djdblaster]

So what would be my next step here please?

 

[2informaticos]

U5750 is the common thing on these 3 keys.
If none of them works, and traces to/from U5750 are surely good, this is a f***g poltergeist...

 

[djdblaster]

I don’t see any other logic too.