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.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.
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?