820-00426 boot loop when trackpad and keyboard are connected at the same time

[MOMOH]

Hello guys, have got 820-00426 , the keyboard and trackpad works okay , however , when I connect them both , the machine would restart continuously, When I connect just the trackpad , it works , also when I connect just the keyboard it works , but both , the machine would constantly restart. After the machine is booted, if I connect the keyboard trackpad, the Mac will work okay , but will not boot with them

 

[2informaticos]

Try another keyboard first.
Monitor SMC_ONOFF_L signal.
Keyboard signal go to PCH through trackpad circuitry.
You cannot discard KB, if TP flex is not connected.

 

[MOMOH]

tried another keyboard and trackpad plus cable , but still same thing, what should I look out for on the SMC_ONOFF_L signal?

 

[2informaticos]

Disconnect TP flex, let only KB connected to MLB.
Then post I2C_IOXP_SCL/SDA voltages pressing some keys.
Also post voltage on SMC_ONOFF_L.

 

[MOMOH]

doing that now

 

[MOMOH]

I2C_IOXP_SCL/SDA = 3.3V stable and SMC_ONOFF_L. = stable at 3.42V


Would also add that the Mac only restart when its booting into the OS .. without OS the machine would not restart and the keyboard/trackpad works okay, its also not the drive nor the operating system

 

[2informaticos]

"I2C_IOXP_SCL/SDA = 3.3V stable"
One line should drop until 0.4V and other to 2.7V when you keep some keys pressed.
SMC_ONOFF_L comes back steady high after pressing power button?

 

[MOMOH]

The I2C_IOXP_SCL/SDA drops as you said but that is when the machine is not booted, however for the machine to boot , I will have to disconnect either trackpad or keyboard and the SMC_ONOFF_L goes back up , upon pressing the power button

 

[2informaticos]

Check PP3V3/5V_S4 with both TP and KB connected.
Also try other TP flex and board.
New chinese TP flex can get problems, many crappies...