1708 - "stick drift" but good stick and POT

[Andrunin]

Hi, I've got a drifting 1708 which is not caused by the mechanical stick or potentiometer.
I tried with a new POT and got the same result:
The axis range is only [-1.0, -0.9] in the gamepad tester.
It does not behave like the usual stick drift really, but more like a shift of the stick center way out of range.

The Ohms Reading from the pot center pin to the outer pins is about 4k with a centered stick, which seems to check out with the other pots.

I did swap the small MCU board on this board. Sticks were good before with this MCU, but idk if this bottom board is good. Any idea what is causing this?

[RDC]

Are you saying that you swapped the SOC board? If so, that SOC board was calibrated to whatever sticks were on the other board, and from time to time that gets done with a real nut butter of a stick, so you'll have to tweak the new one real good to get it to center back up.

[Andrunin]

Yes I swapped that small SOC board with the MCU on it. I also swapped the joystick modules over because I had already removed the old ones from the target board.

Only one axis of one stick has the bad center offset. Maybe I mixed the modules up when I put them back in. But then wouldn't the reading for the other stick be way out of center too? I was worrying I messed up the BGA solder joints or something in the SOC board, but you think it's all good there?

[RDC]

The Stick lines run straight to the MCU on the SOC board, so there's not really anything on there to 'drag' it off center. If you can still move the Stick around normally and have the full range, and can get it to center by hold it, then everything should still be good, just need to tweak that one POT a bit.

[Andrunin]

I found the culprit, but damn was it a sneaky one. I tried to twist the pot hard enough, but it would have involved trimming the pot shell lol. Closely inspecting the trace between the mid pin and the SOC board sure enough the pad of that trace was slightly angled and making contact to a neighbor pad. Luckily an easy fix. thanks for the input

[RDC]

Which axis had the issue?

[Andrunin]

Left Stick, Y axis