M5126 Keyboard acting weird

[glay78]

After recapping my M5126, it works however keyboard is acting weird, here are the findings.

1. number 3,4,5 and 6 is not working.

2. alphabet U and D will cause system error.

however I tried

- changing keyboard

- switch over to RHS with mouse

- changing keyboard ribbon cable 

all doesn’t works. 
however external ADB keyboard will work perfectly. 
 

checked C116 Caps and the connectivity is correct. It was working well before recapping. 
 

what could be wrong? I’m short of this step to have a perfect M5126. 
 

anyone has an idea where to start tracing this problem

 

[techknight]

broken traces between the keyboard connector and the keyboard controller chip. 

Try plugging in the keyboard on the right side instead of the left side to see if the problem goes away. the caps eat the traces right there on the left hand side where the power controller circuits are, and so are the keyboard traces. 

 

[glay78]

broken traces between the keyboard connector and the keyboard controller chip. 

Try plugging in the keyboard on the right side instead of the left side to see if the problem goes away. the caps eat the traces right there on the left hand side where the power controller circuits are, and so are the keyboard traces. 

thank you for replying! I’ve seen so much about your repairs!

yes I tried plugging to the right side and the same issue. Even changed a keyboard and it’s the same.

 

[techknight]

thank you for replying! I’ve seen so much about your repairs!

yes I tried plugging to the right side and the same issue. Even changed a keyboard and it’s the same.

Then you need to follow the schematic in the keyboard section and verify all the traces from the two sockets back to the keyboard controller IC. 

If that verifies good, then replace keyboard IC. 

 

[glay78]

Ok great I’ll do that, no choice 

 

[glay78]

Then you need to follow the schematic in the keyboard section and verify all the traces from the two sockets back to the keyboard controller IC. 

If that verifies good, then replace keyboard IC. 

@techknight how do I read the schematics for the this? Do you mind guiding me a bit?

I know U12K is the Keyboard chip. But how do I read the pins and which are the 2 sockets?

 

[techknight]

These are one of those sheet-by-sheet style schematic. 

Regardless, you have to follow the connection points back to another sheet which has the pinouts of the connectors. 

I don't want to sound cold, but I cant really teach you how to read a schematic, as its a super involved process and I am not really a good teacher. If you don't know how to read schematics, you have a long long way to go. 

May I suggest youtube videos or something for basic electronics training and schematic reading. I know there are some good ones out there. 

 

[glay78]

These are one of those sheet-by-sheet style schematic. 

Regardless, you have to follow the connection points back to another sheet which has the pinouts of the connectors. 

I don't want to sound cold, but I cant really teach you how to read a schematic, as its a super involved process and I am not really a good teacher. If you don't know how to read schematics, you have a long long way to go. 

May I suggest youtube videos or something for basic electronics training and schematic reading. I know there are some good ones out there. 

Thank you for your tips. Problem solved, J13 pin 13 trace is broken. Fixed. Perfect working piece now. 
 

I’m glad I part of this forum. Next are my sad Macs M5120 which shows Ram error. 

 

[techknight]

Good

 

[glay78]

Good

Thank you. 
 

for my M5120 which have error codes

0000 0003

0000 00FF

0000 0003

0000 FFFF

how should I troubleshoot?