Switch Lite ZL always "pressed" (high resistance against GND)

[mvmiranda]

Hello all,
Long time since I've posted here and I'm back again with a brand new issue I'd like to discuss with you and get some inputs.

I received this Switch Lite the customer attempted to mod with a HWFLY Lite 4.1 and ended up partially removing the mainboard FPC white lid (the FPC that connects the button board to the mainboard) while the battery was plugged in.
He said he tried to turn on the console a couple of times without it properly attached and ultimately gave up.

I received the console, swapped the FPC, finished the mod install and then assembled it. I proceeded to test it and noticed the ZL was not working in "Test input devices" and that it automatically ended after 1 or 2 seconds.
I then noticed a message that reads "Hold down any button to end the test" and I figured it might be always pressed.

The buttons works by connecting the line to GND.

I did some tracing and found the complete path the ZL button takes.
It starts in here:


Then it follows the flex cable which leads to here (it then follows this small path where we can see a capacitor to filter the line):


The trace enters the board, travels the 9 layers and end in the STM32F038C6 microcontroller:


Measuring the button against GND (black tip in GND) in diode mode (beeps in continuity) I noticed we have a 690 Ohms value. The ZR doesn't measure anything (OL) unless it's shorted to GND when it closes the circuit and beeps.
I have other Switch Lite boards and consoles in here and I can confirm the ZL follows the same logic as ZR (OL with no value when measuring against GND).

I removed every component in the line (the FPC connector, filter capacitor and microcontroller) and the value is still present, so my assumption here is that the trace is damaged internally.
Maybe a high voltage generated by the partially connected FPC charred/burned the trace near a GND plane/trace and it's now producing this value I see in my multimeter.

Does anyone here ever saw this issue?

Thanks!

 

[rip-it-up]

i dont really know.
the closest thing ive had is, when i pressed a certain button (think it was one of the triggers) the console would enter sleep

mine was corrosion. and it fixed it.

id personally test with a different daughter board, and inspect the zifs on the main board/ make sure those tiny caps above the main pcb/daugther baord pcb aint missing.

 

[mvmiranda]

i dont really know.
the closest thing ive had is, when i pressed a certain button (think it was one of the triggers) the console would enter sleep

mine was corrosion. and it fixed it.

id personally test with a different daughter board, and inspect the zifs on the main board/ make sure those tiny caps above the main pcb/daugther baord pcb aint missing.

Thx for the input!
I've, actually, already swapped everything!
I swapped the whole mainboard into another known good console (case, buttons, daughterboard, LCD, etc etc).

When I confirmed the board was the "culprit", I removed all the components in the line: the FPC connector, capacitor and even the microcontroller itself. No matter what, the value is still present in the line.

 

[rip-it-up]

Thx for the input!
I've, actually, already swapped everything!
I swapped the whole mainboard into another known good console (case, buttons, daughterboard, LCD, etc etc).

When I confirmed the board was the "culprit", I removed all the components in the line: the FPC connector, capacitor and even the microcontroller itself. No matter what, the value is still present in the line.

i dont think ill be able to help, you seem to know what your doing more than me.

if you connect a separate joycon via bluetooth does it let you press the trigger? ( not sure why im asking that im just curios

 

[mvmiranda]

i dont think ill be able to help, you seem to know what your doing more than me.

if you connect a separate joycon via bluetooth does it let you press the trigger? ( not sure why im asking that im just curios

hmmm!
I haven't thought about it...
Will test and report back
Thx for the tips!

 

[blekpentha]

Have you solved this issue? Im having exactly the same issue as you are.

 

[de9ed]

swap the daughter board was the answer

 

[Nandoazevedo30]

hmmm!
I haven't thought about it...
Will test and report back
Thx for the tips!

I have exactly the same issue, I swap the daughter board but still nothing, test with another joy con and the ZL doesn't work either

 

[jkyoho]

I have exactly the same issue, I swap the daughter board but still nothing, test with another joy con and the ZL doesn't work either

then very likely you need to replace to STM32 chip

 

[Nandoazevedo30]

then very likely you need to replace to STM32 chip

I did it too, I replace the stm32 from a dono board and ZL still doesn't register, I'll try find the full trace of the line to see where it goes after the stm32