Repair Xiaomi Mi Smart LED Desk Lamp Pro

[davidbo]

Hi everyone,

I recently bought a Xiaomi Mi Smart LED Desk Lamp Pro for my desktop. To goal is to use it for circadian lightning (changing between white and cold warm depending on the position of the sun). The lamp has an ESP32 chip for connectivity
I changed the firmware of my Xiaomi Mi Smart LED Desk Lamp Pro to EspHome to make it compatible with my Home Assistant automation. Flashing went fine but it seems something got damaged along the way

There are two different LED strips in the lamp - a cold white and a warm white one and they get mixed depending on the configured light. The power supply delivers 12v with 1A and the LEDs run on 24v. The cold one works just fine - I can adjust brightness and adapt to the overall light settings.

The warm one works sometimes. After turning it on it usually works for some time after it starts blinking and then turns off. The voltage for the LEDs drops back to 12v. When I configure the lamp via the rotary encoder it works just fine. As soon as I release the knob (touched by hand) the light stops working again. I checked if the encoder casing is connected to something via my multimeter and I could find anything. The circuit has a similar behavior if I place my finger close the circuit. When the LEDs were off they started to blink rapidly.

This is the PCB.



The right-hand side of the PCB (looking from the top) seems to be responsible for the warm white LEDs. I assume on the PCB is some kind of step up converter and measured the output voltage across C22.

On the back are some pins but unfortunately, I ripped them off by accident. That's why I had to solder to the ESP32 pins directly to flash them and they look not as nice as before. I checked them and there are no short circuits to my knowledge.

I have a few questions:
- Since touching the rotary encoder changes the behavior I assume it changes some capacity value on the board. Is worth trying to replace them?
- Might the rotary encoder itself be the issue?
- What else can I do to dig deeper into the issue?
- What can I do to identify other components? e.g. Q6 which seems to be some kind of transistor

Any help is appreciated!
I only have a multimeter to measure any data points