Fixit Clinic 2024-10-20

This Fixit Clinic was held at the Hayward Library. There weren’t very many people.

I worked with another fixer on a Japanese foot-warming table that wouldn’t temperature regulate and stayed on constantly. It was constructed with two quartz heating elements controlled by a bimetallic thermostat mounted on its underside, with reflectors to direct all the radiation downwards. They were protected by a steel cage, with a sort of felt coating to decrease its thermal conductivity in case someone contacted it. The table was meant to be completely covered by a blanket to create an enclosed space underneath it to be temperature-regulated.

We were able to trip the thermostat by pointing a heat gun on low power at it from 200 – 300 mm away, though it had to get fairly hot to do so. We also tried covering the heater assembly with the lid of a banker box, protecting it from any direct radiant heating using a silicone baking sheet placed in front of the heating elements, and found that while the thermostat could trip, it needed to get quite hot to do so. (So hot that the silicone sheet started smoking, though whether this was because of oil and food residue or the silicone itself thermally decomposing I’m not sure.)

The thermostat had no adjustment screws of any kind, so we were unable to calibrate it that way. However, it was constructed with the temperature knob advancing a screw which pressed the contacts together (okay, this is a simplification…) to adjust the temperature at which the thermostat tripped. We determined that by bending back the limit stop (which constrains the motion of the knob) on the thermostat, and turning it in the “colder” direction by a full turn, we could shift the thermostat’s entire temperature range significantly downward, so much so that for about ⅔ of its temperature range (at least for room temperature on that day), it was open. Upon consulting the owner, she said that was fine, and she would try it.

After that, there weren’t any more new fixes, so I inserted myself into a group that was fixing a milk frother, of the same owner as the table. The owner had put cocoa powder in it, whereupon the motor had stopped working even after cleaning it out. After a lot of troubleshooting, we found that the motor was physically stalled and the shaft simply wouldn’t spin. We took it out and cleaned some rust and cocoa powder from around the bushings, and it ran just fine despite being run at a stall for so many times in the course of troubleshooting. The rust was possibly due to the rubber gasket that sealed the motor shaft against the liquid leaking over time, though it could have just been that the cocoa powder “gunked up” everything.