Macbook Air 13ich A1466 trackpad 923-0438 and keyboard schematic request

[Sierra89]

Hello!
I've used this forum a lot in the past and always found the information I needed to keep on learning and solving the problems. This time, though, I haven't been able to find what I needed so I wonder if any of you could share it.

I have a 2017 Macbook air A1466 that won't turn on.
I can turn in on with the power pads, and even shorting the SMC_ONOFF_L
line to ground in both sides of the flex cable (mother board and trackpad board), I also changed the whole keyboard assembly to a new one which works well.

All this leads me to think that my problem is in the circuit embedded in the trackpad. So it would be very useful for me if somebody could share a schematic of the A1466 trackpad (923-0438 if I'm not mistaken) or even for the keyboard, if the power key is routed directly through the keyboard connector to the flex board that goes to the main board I could just run a jumper wire.

Thanks a lot for your help!

Edit: I've also checked all Voltages in J4800 connector and all make sense (including SMC_LID at 0V with closed lid and 3.4 with open lid). It's just that a power button press won't drive SMC_ONOFF_L low.

[piernov]

Re: Macbook Air 13ich A1466 trackpad 923-0438 and keyboard schematic request

No schematics available for touchpad and keyboard. It's almost always a keyboard problem, but sometimes the touchpad and its cable can be the problem as well.

[Sierra89]

Re: Macbook Air 13ich A1466 trackpad 923-0438 and keyboard schematic request

No schematics available for touchpad and keyboard. It's almost always a keyboard problem, but sometimes the touchpad and its cable can be the problem as well.

I'm 99% sure it's not the keyboard and all other keys work in 2 keyboards I've connected to it, and power key fails in both. It's also not the cable from the touchpad to the motherboard because if I manually short the data line responsible for the power button signal to ground (thus activating it as it's active low), the device powers on/off, and this remains true at both sides of the cable.

It's a shame there are no schematics, it would be such a simple fix if I knew where I can bridge that data line to so that it connects to the power button...

Thanks for your help and time in any case!

[audiomodder]

Re: Macbook Air 13ich A1466 trackpad 923-0438 and keyboard schematic request

I'm 99% sure it's not the keyboard and all other keys work in 2 keyboards I've connected to it, and power key fails in both. It's also not the cable from the touchpad to the motherboard because if I manually short the data line responsible for the power button signal to ground (thus activating it as it's active low), the device powers on/off, and this remains true at both sides of the cable.

It's a shame there are no schematics, it would be such a simple fix if I knew where I can bridge that data line to so that it connects to the power button...

Thanks for your help and time in any case!

Good news my friend, I had this same problem and reverse engineered the protocol completely. I documented how the keyboard interface works and how you can measure and repair / workaround the power key, in exhaustive detail here:

https://www.youtube.com/watch?v=3QbX2XuuY8w
All repair docs: ********************
(also attached here)

Some summary from Readme:
1. SMC_ONOFF_L goes low to turn on SMC/CPU
this comes directly from keyboard with only
a 1K ohm (R5710) standard resistor for logic and parallel
capacitor (C5710) for debouncing.

2. All other keys for SMC RESET (option, left
shift, control) are active HIGH, connecting
to PPV342_G3H when pressed. These go through a NAND (u5750 / SLG4AP021) to create SMC_TPAD_RST_L.

3. When both SMC_ONOFF_L and SMC_TPAD_RST_L are low, SMC is RESET by U5010 (SN0903048)

Page 53 Macbook 13" for NAND SMC RESET
Page 53 Macbook 13" for Keyboard conn.
Page 41 Macbook Air 11" for SMC RESET

if power key press does not create 1K (R5710) to GND on SMC_ONOFF_L, keyboard is broken.

**SPECIAL THANKS TO**
Louis Rossman
Badcaps.net/forums (yall are my heroes!)
OpenboardView free software!
SumatraPDF free software!
************************

[howardc64]

Re: Macbook Air 13ich A1466 trackpad 923-0438 and keyboard schematic request

liquid spilled 2013 A1466 with a left shift key stuck pressed. Used audiomodder's inspiration and found a key probe point on the trackpad to determine if fault was trackpad board or kbd. Turns out it was kbd.

Easiest test would have been a known good trackpad (easy to replace+test). But not available in my case (initially, eventually got hold of one to confirm diagnostic result) and probably not available for most people who don't have a shop or multiple of the same models around.

As audiomodder showed, left shfit, opt, and ctrl keys are special. They trigger SMC reset at boot. Therefore have dedicated lines rather than a column/row matrix like most keys. On the 2013 A1466, the SMC manual reset isolation logic is integrated into a single 11 pin chip on the trackpad module. This 11 pin integrated chip seems common for this era. A1502 has the chip on logic board. Thus boardview and schematics provide clear diagnostic trace points.

Attached is a part of the 13 A1466 trackpad. I've labeled this 11pin (1 pin in center hidden from view) chip according to A1502 schematic counterpart. Pin 1 (left shift) is the probe point to see the left shift key voltage both pressed (3.42v) and unpressed (0v pulled down presumably by chip internal resistor) In my case, unpressed shows a range between 1.2 to 2.8v indicating a short to the 3.42v supply in the keyboard. When known good 2nd trackpad became available, this result was confirmed. A couple of pics are attached for reference.

BTW, googling showed a lot of stuck pressed left shift key problems on Macbooks. Perhaps the reason is it is right next to the 3.42v line on the keyboard flex/connector layout. Corrosion from moisture would cause current to flow from 3.42v line to left shift line signaling its being pressed. Any liquid spill on the keyboard likely trap moisture inside above the black protective plastic. Trackpad also sits above the flat battery offering another source of sitting moisture for corrosion.

Anyway, thanks to audiomodder (and originally Louis Rossman of course) for the inspiration.