"electroninja" wrote in message
ups.com...
| Located thermistor--results follow:
| - Thermistor resistance reading was 275K ohms
| - Substituted variable resistor in circuit for thermistor and ran
| system operational testing for multiple values from 16K-2.2Meg ohms
|
| --Result: Microwave ran for approximately the same length of time
| before shutdown (40-60 sec) except for extreme resistance tests ie
| extreme highs and lows then shutdown was 10-38 seconds.
|
| Conclusions: Suspect control board problem--haven't located one from
| suppliers yet--have have only found a control board varistor
| replacement part for this unit. Assume a varistor is a variable
| resistor--part photo from supplier looks like a small capacitor.
|
| Comments appreciated regarding possible function of varistor in
| circuit--are they possibly used in timing control circuits?

No. They may be voltage variable (varistor) or temperature variable
(thermistor, PTC or NTC). Very unlikely that they are used for timing. Is
this a sensor model?

N