PrincessPrinPrin wrote:There are two resistors in the PTC with a common side (the middle pin). One resistor is much higher than the other so you need to test resistance (not continuity) and adjust the meter manually if it's not autoranging.
OK, the thing that I didn't understand is that the PTC and NTC were thermistors (a word I didn't know). Googling PTC eventually led me to PTC and NTC thermistors, which I read about and understand at least a little bit now, thanks.
I was unable to find a datasheet for my specific NTC thermistor, but I looked up how to test thermistors in general. Pins 1 to 2 showed a steady resistance, until I applied heat to pin 2, at which point the resistance dropped steadily. Same thing for pins 2 to 3 -- steady resistance, but applying heat caused the resistance to drop. Like you said, pins 2-3 had a much lower resistance than 1-2, low enough to trigger the continuity beep on my diode tester, but I don't think it's actually shorted. I think this part is good, and I put it back into the chassis.
Going back to testing whether there are any other shorted components on the board -- I have a small concern about the area around the voltage regulator. When I do a continuity test (diode mode) on the traces where the voltage regulator was, I get the following:
B-E - no beep, resistance remains steady
B-C - no beep, resistance slowly rises until it reads open
C-E - Initial short beep, but resistance rises until it reads open. To me,
My concern is that initial short beep on C-E, indicating low resistance between the collector and the emitter. But then, something happens (a capacitor filling up?) that causes the resistance between C-E to increase. Does this seem normal?