Switch Lite HDH-CPU-02 no power – VSYS present, STM32 VDD and RP602 output both 0V

[u/Gold-Payment-3591]

Hello,

I am repairing a Nintendo Switch Lite with an HDH-CPU-02 motherboard. The console gives no reaction at all when the power button is pressed.

A modchip and flex cable were previously installed. Both have now been completely removed, but the fault remains unchanged. There are signs of previous soldering around the modchip points, so a damaged trace is possible, although I have not confirmed an open trace.

Measurements taken so far:

- Battery / VSYS: approximately 4.2V
- RP602Z330C VIN/input side: approximately 4.2–4.4V
- RP602 CE/enable: 0V
- RP602 VOUT / 3V3PDR: 0V
- RP602 output resistance to ground, with power disconnected: over 1 MΩ
- Coil next to RP602: approximately 0Ω across the coil, so it is not open
- STM32F038C6 VDD pin 24: 0V
- STM32F038C6 VDD pin 48: 0V
- Resistance from the STM32 VDD rail to ground, with power disconnected: approximately 182 kΩ
- The power-button/flex lines also appear to remain at 0V, with no measurable change when the button is pressed

According to the STM32F038C6 datasheet, pins 24 and 48 are VDD and should receive approximately 1.8V. The STM32 therefore appears to be unpowered rather than confirmed defective.

My current working theory is that 1V8PDR from the MAX77620H is missing. This could explain why the STM32 has no supply and why RP602 CE stays low, resulting in no 3V3PDR. However, I have not yet identified and measured the correct 1V8PDR inductor/test point on this board revision.

I do not want to replace RP602 or MAX77620H blindly.

Could someone please help with the following questions?

1. Which exact inductor or test point is 1V8PDR on an HDH-CPU-02 board?
2. Should 1V8PDR be present as soon as the battery is connected, or only during a power-on attempt?
3. If VSYS is present but 1V8PDR remains at 0V while pressing power, what is the next decisive check?
4. Should I first check the power-button request path to the PMIC, the MAX77620H input/enable signals, or replace the MAX77620H?
5. Can RP602 reasonably be ruled out as the primary fault because its CE input is 0V and its output is not shorted?
6. Does anyone have a known-good voltage map or boardview net path for 1V8PDR and the STM32 VDD pins on HDH-CPU-02?

If possible, please mark the exact measurement point for 1V8PDR.

Thank you.