DMM repair
..., Tue Aug 01 2006, 02:57AMOk, I accidentally gave my protek 506 a bit more juice that I was supposed to (well I thought it was a low voltage transformer...)
and it arked over in the traces for the mode selector dial... But that wasn't much of a problem (just scrape off the carbon and all is good)BUT there were 2 components in series with the input labled ptc1 and 2 that look like thermistors, ao I am guessing that they were ptc thermistors. The the only problem is that I don't know what type... I measured the one that was not burnt and it read about 500ohms, but if I replace the other one with a 500ohm resistor the resistance calibration is off (it reads like 75ohms at a dead short). If I short either of the 2 thermistors it reads correctly...
Does anyone have one laying arround that you could measure for me to see what they should be? For now they are shorted, but I would like to put them back in
Re: DMM repair
Wolfram, Tue Aug 01 2006, 01:29PM
PTC1 = 350.8 ohms and PTC2 = 355.6 ohms when measured in-circuit. The temperature here is around normal room temperature. However, my Protek is broken in some way too, because a dead short measures as 256 ohms in resistance mode, so I wouldn't trust these numbers blindly.
Wolfram, Tue Aug 01 2006, 01:29PM
PTC1 = 350.8 ohms and PTC2 = 355.6 ohms when measured in-circuit. The temperature here is around normal room temperature. However, my Protek is broken in some way too, because a dead short measures as 256 ohms in resistance mode, so I wouldn't trust these numbers blindly.
Re: DMM repair
..., Tue Aug 01 2006, 03:15PM
hmm, perhapse a bulk buy once we get the right number
..., Tue Aug 01 2006, 03:15PM
hmm, perhapse a bulk buy once we get the right number
Re: DMM repair
Conundrum, Thu Aug 03 2006, 06:26PM
lol.. sounds like my meter. i think ptcs are a type of overvoltage crowbar.
-A
Conundrum, Thu Aug 03 2006, 06:26PM
lol.. sounds like my meter. i think ptcs are a type of overvoltage crowbar.
-A
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