In line bathroom extractor resistor overheating

[HobGoblyn]

Hi

Bathroom fan started oscillating on startup, for a few days it came on, went off, came on etc for a couple of mins before finally staying on properly.

Then it simply oscillated.

Took it out, need to replace CBB61 capacitor.

But I also noticed scorch marks either end of a resistor.

Resistor looks like it’s red, red, pink, gold under my microscope, presuming the pink is violet, (definitely not orange under microscope) then it should be 220 Mohm. But it measures at 22.72Kohm, which would mean the third colour is orange not violet, with the naked eye I suppose it’s orangeish

The scorch marks look to me like the resistor is getting too hot.

Any suggestions please (pics attached)

Thanks

[Gyro]

Bathroom fan run-on timers like that use that resistor as a mains dropper in combination with a zener diode, to provide the [Edit: 12-15V] controller supply (basically a 4000 series logic chip and a small Triac). The resistor does dissipate a fair amount of heat in the process, but the PCB is an ordinary phenolic which browns very easily when exposed to long term (presumably years if the electrolytic capacitor failed) moderate temperatures. Yes, 22k sounds right - around 10mA supply current, so the resistor is dissipating 2.4W.

You could maybe try a higher wattage resistor, or stand the resistor further off the board, but the housing is cramped and you don't want the resistor getting too close to the plastic case molding instead. It's working as designed anyway, the PCB really doesn't look that bad.