Faux' blog

Failed Quooker Cube

I received a failed Quooker Cube chiller unit.

Upon connection to power, nothing would happen; no lights, no sounds.

Slightly weird board layout, with the main voltage conversion "primary" situated a significant distance from the mains input "power supply":

Investigation revealed the voltage on the secondary capacitors was only around one volt. The rectification diodes test fine.

Investigating the feedback circuit, I noticed that the diode in red is short circuit; 0 Ohm in both directions. Verified out of circuit.

I believe this is D5 for the AP3983R, acting as the main power supply for the chip, from the feedback winding, after R1/R2 provide the bootstrap.

By failing, it's pulling the feedback pin high, resulting in limited switching?

Removing the diode appears to have improved matters, but I await a replacement before claiming a full fix.