A bit over a week ago I mentioned that my washing machine has decided to die - well, to forget how to spin-dry, which amounts to the same. The off-balance detection was stuffed: it would start the motor in high-speed mode but switch off after <1s, repeat 3x, give up and hand me soaking clothes. (Same behaviour with an empty tub.)
The two-year warranty ran out a year ago (no surprise here). So I dismantled the machine and checked sundry other things (like inspecting/reseating the motor brushes) but couldn't find any mercury switch or other obvious means of detecting a bouncing tub. Accordingly, I couldn't fix it directly.
I have no precise idea how they detect an out-of-balance tub, except that the motor has a hall-effect rpm sensor which I think could work (assuming that the tub slows down and speeds up asymmetrically if it's wobbling). Net result of X hours of ripping apart, tracing wires and so on: all inspectables are fine but it still won't work. The only remaining part was the part-mechanical-part-electronic control board, and these things usually aren't cheap.
After a long search I figured out the proper part number (the fact that the machine is a rebadged Electrolux didn't make that search any easier), and would have been able to buy it online at various overseas retailers...for about $150-200..
Luckily ebay came to the rescue: somebody sold one as new-old-stock locally for $50. Add $26 for express postage, 10min for installation and I have a washing washer again. Very nice.