Mike Monett wrote: > [EMAIL PROTECTED] wrote: > > >Phil, > > > I didn't believe that the thermoswitch was the problem, at first, > > chiefly because of the simplicity of operation. Eventually, after > > checking wiring, a carbon resistor that is in series with the > > thermoswitch, and components around the inner oven control > > circuitry, I removed the thermoswitch to the bench. > > > After hooking up to a ohmmeter and using a 60 watt light bulb as > > the heat source, I found that I could duplicate the a pulsating > > open / close as before. I first focused on the bulb leads and > > eventually completely removed the old leads and rebuilt each one > > and did all new soldering under magnification. The problem remains > > the same. > > > I'm ready to move on at this point noting that this component > > failure has me stumped and that the fault is most likely internal > > to the thermoswitch (as strange as this seems). Years ago, when I > > first saw how internal temperature worked using the mercury > > thermometer switch, I remarked that it was one component that > > would never fail. HA! That statement came back to haunt me. > > >Best, > > >Russ > > I have been following this thread with some interest, as I expect to > have similar equipment in the future. What is amazing is how you > discovered the problem! > > Like you, I would not have believed a mercury switch could fail. But > a quick search showed the contact can oxidize, and gave several > patents aimed at solving the problem: > > 1. Reduction of oxides in a fluid-based switch - US Patent 7071432, > 07/04/2006 > > Often, oxides may form within the switch and inhibit proper > functioning of the switch. For example, the oxides may increase or > decrease the surface tension of the liquid metal, which may increase > or decrease the energy required for the switch to change state. > > Oxides can lead to poor switch performance, and even switch failure, > because they lessen or prevent a switching fluid from wetting > surfaces it is supposed to wet.
Hmm... but capacitive sensing should still work well. Cheer, Magnus _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.