Troubleshooting PHILIPS Sonicare Diamond Clean: Pressure sensor not working after minor liquid damage
Hello everyone,
I’m working on a PHILIPS Sonicare Diamond Clean electric toothbrush that stopped turning on after minor liquid exposure to the PCB.
Initial repair: I cleaned the board, found a blown fuse, and replaced it. The toothbrush now powers on and runs, but a new issue appeared: the pressure sensor is not working.
Troubleshooting steps I've already taken:
- Installed a known-good pressure sensor assembly (sensor + flex cable).
- Replaced the entire vibration motor assembly.
- Replaced the OM9663 IC.
- Checked for shorted capacitors (none found).
- Verified all resistors in the surrounding circuit (all are intact and measure correctly).
The exact symptoms: Visually, the PCB looks completely pristine and undamaged now. However, the pressure sensor remains unresponsive under normal operation. Interestingly, if I manually place the pressure sensor very close to the magnet, it triggers constantly as if heavy pressure is being applied to the shaft (the LED flashes and the vibration mode changes). In any other normal position, the sensor does not react at all.
Has anyone encountered this specific behavior? Could this be an issue with a degraded magnet, a micro-fracture in a trace, or something deeper like an MCU fault?
Any suggestions or schematic hints would be greatly appreciated!