A2681 MacBook Air 13" Short on board question.

[Stephen]

Ok update: Good news! found a Resistor (SYS_DETECT) that was not hitting P3v_8. replaced and now battery is charging!

[mon2]

Praise THE Lord!!! Thanks for this!! Finally.

So you shorted the resistor mentioned earlier?

You shorted R51B1?

Thanks for the feedback. It is a first for this model.

[mferna14]

Read all., Stephen, as you said you never replaced the LCD Screen, its original... So our problem still persists!!! Hopefully this might be the resistor that has blew out on the logic board when the our laptop was replaced with a new LCD Screen from the Chinese sellers. & the botton line is that if these screens are used, what is the probability that this resistor & some component on this rail might blow up again because the LCD Screen is still the same. I guess that something is wrong with the LCD Controller board (TCON) board which we purchase from China. What are your thoughts???

[Stephen]

Praise THE Lord!!! Thanks for this!! Finally.

So you shorted the resistor mentioned earlier?

You shorted R51B1?

Thanks for the feedback. It is a first for this model.

The resistor in question was R51A0

Well, I am still diagnosing this stupid board, I have fixed the battery not charging and recognized issue, I noticed the resistor was shorted to ground and it had some eaten pad underneath under the microscope, however I did replace it and the original battery was detecting but not charging, so I swapped out the battery and now the new battery is charging and working, HOWEVER, I am facing a keyboard not typing and track pad not clicking issue but the trackpad works (it has the mouse and you can click and move but you don't feel the haptic feedback) The keyboard isn't even typing any letters whatsoever, I looked at the lid sensor and its not bad since the lid is fine and it doesn't go to sleep, SOOOO I am not fully out of the woods yet.

[Stephen]

Read all., Stephen, as you said you never replaced the LCD Screen, its original... So our problem still persists!!! Hopefully this might be the resistor that has blew out on the logic board when the our laptop was replaced with a new LCD Screen from the Chinese sellers. & the botton line is that if these screens are used, what is the probability that this resistor & some component on this rail might blow up again because the LCD Screen is still the same. I guess that something is wrong with the LCD Controller board (TCON) board which we purchase from China. What are your thoughts???

There is a possibility, but not in this situation, but the knowledge can be shared. I believe the issue with this board was due to severe amounts of liquid damage. I won't lie, I replaced about over 10+ components on this board. I have been diagnosing it for 2 weeks here and there. Going through customer repairs and when I have a brain refresher I come back and find more issue and fix them. Now that I have most of the hard work one I just need to diagnose this keyboard not typing issue.

[mferna14]

There is a possibility, but not in this situation, but the knowledge can be shared. I believe the issue with this board was due to severe amounts of liquid damage. I won't lie, I replaced about over 10+ components on this board. I have been diagnosing it for 2 weeks here and there. Going through customer repairs and when I have a brain refresher I come back and find more issue and fix them. Now that I have most of the hard work one I just need to diagnose this keyboard not typing issue.

Stephen., the Trackpad/Keyboard contr'l board is the issue, loacated at the far right end of the logic board. I had this same problem a month back, no trackpad moment at all. The keyb was acting eratic. I observed under the MS the controller board had liqiuid spill on it. I cleaned it but did not work. Ordered the Contr'l board & all worked fine. BUT BEFORE ORDERING THE CONTR'L BOARD, TEAR OPEN the trackpad, you might see liquid spill on that small contr'l board too, the Flex cable connector. Check it under MS, you will see it well.

[Stephen]

Stephen., the Trackpad/Keyboard contr'l board is the issue, loacated at the far right end of the logic board. I had this same problem a month back, no trackpad moment at all. The keyb was acting eratic. I observed under the MS the controller board had liqiuid spill on it. I cleaned it but did not work. Ordered the Contr'l board & all worked fine. BUT BEFORE ORDERING THE CONTR'L BOARD, TEAR OPEN the trackpad, you might see liquid spill on that small contr'l board too, the Flex cable connector. Check it under MS, you will see it well.

I replaced that control board with another one and same issue both control boards don’t have liquid damage on them. They look new. I may try another board and see if it works but chances are it’s a board related issue still

[Stephen]

Update: not the controls boards. Replaced it three times. nothing. It has something to do with the logic board and I cannot seem to pint point it. I looked at the track pad area that connects to the track pad and all looks well. Now I am dumb founded because this is the final issue and I have no idea where to start since the IO board is working.

[mon2]

Remove all power. Meter in DIODE mode. Red meter probe, yes red to ground. Black meter probe to the point to test.

Test on J0301, the following:

I2C_KBD_SCL
I2C_KBD_SDA

The above are the I2C / SMBUS interface lines used to communicate with the keyboard decoder for the keyboard matrix (sans Keanu).

[Stephen]

Update: So I was curious if the computer would go into DFU to see if the keyboard worked this way, I did replaced the trackpad connector since it did look a little damaged, but I still had this issue persisting, so I was curious, I tried to put the computer into DFU and it went into DFU, so the computer recognizes the keys are being pressed, otherwise DFU would not work. I am doing a DFU revive however the DFU revive was unsuccessful. THIS COMPUTER IS ANNOYING BTW. I have trouble shooted everything entirely, but now I am curious if the computer has another issue hence why the keyboard was not functional. The device was in recovery at first, I did a few restarts and the track pad would click and then nothing and went away and the keyboard would not type. So I am generally curious what's going on.

[mon2]

The keyboard is operating by 2 x port expanders @ UT101 and UT102. Each is an I2C slave with its own bus address. Confirm that the ESD TVS diodes are not defective which will make the keyboard appear to be defective.

[Stephen]

Remove all power. Meter in DIODE mode. Red meter probe, yes red to ground. Black meter probe to the point to test.

Test on J0301, the following:

I2C_KBD_SCL
I2C_KBD_SDA

The above are the I2C / SMBUS interface lines used to communicate with the keyboard decoder for the keyboard matrix (sans Keanu).

you mean JT201?

[Stephen]

The keyboard is operating by 2 x port expanders @ UT101 and UT102. Each is an I2C slave with its own bus address. Confirm that the ESD TVS diodes are not defective which will make the keyboard appear to be defective.

Would this matter even if the keyboard responds to DFU commands?

[Stephen]

This is the error message I am getting when trying to revive the computer. The computer goes into DFU so keyboard commands respond. Track pad clicks constantly when it fails. Lid sensor is not liquid damaged and looks brand new.

I am going to order a new lid sensor out of curiosity. Calibrate it and see if that's the reason. But I did look up error 1 and it points to Battery, however the battery is charging and holding a charge when not connected to power and depletes normally.

[Stephen]

Hey mon2 any idea what it could be?

[mon2]

Are you sure the keyboard is doing anything? Are you able to enter the DFU without touching the keyboard? Attempt it.

[Stephen]

on M series Macs you need to enter DFU with holding keys down am I not correct? Basically right SHIFT ALT OPTION Power button etc.

[mon2]

If the keyboard is truly working, are you able to force this laptop to boot from an external known good OS and drive?

[Stephen]

The Laptop didn't revive so I have the exclamation point error until I fix this issue. So possibly won't be able to boot externally until I resolve this issue. Since I tried to do a DFU revive it couldn't complete and now it won't load the OS. So gotta fix that as well. I want to just chuck this computer in the trash (jokingly)

I ordered a good top case with a good keyboard, battery and trackpad w/ cable, and good daughter IO board. I also ordered a new lid sensor even though this one is working. I will program the new lid sensor, swap out the top case and see if I persists. I will get back to you with my findings.

[mon2]

The new generation of models appear to be more and more crapware designs that are throw aways...yet, the fans keep on purchasing them. Suspecting a flash fault but even that will be a no fix.