SDT-100 1k Thermistor Replacement?

Love Vintage

Love Vintage

Active Member
I am working on a Marantz 300DC and need to find a substitute for the SDT-100 1k Thermistor. I don’t know much about thermistors and don’t know how to find a sub, any help would be greatly appreciated.
Terry
 
A google search shows a NTC thermistor with that ID. Thermistors basically divide in NTC and PTC, which means the resistance goes lower or higher with the temperature. I think any thermistor with the same value and same type will work.

Try to find a datasheet , the resistance at 25ºC of that specific part, and the max. and min. resistance, will be detailed there.
 
elnaldo said:
A google search shows a NTC thermistor with that ID. Thermistors basically divide in NTC and PTC, which means the resistance goes lower or higher with the temperature. I think any thermistor with the same value and same type will work.

Try to find a datasheet , the resistance at 25ºC of that specific part, and the max. and min. resistance, will be detailed there.
Click to expand...
Thanks for the great information, I spent all evening last night looking for a spec sheet but came up with nothing. If anyone has a suggestion of a good place to look up vintage thermistors please let me know,
Terry
 
PM AK'er Catrafter. He's big into rebuilding Marantz's and would probably know the answer. Also do a search in the Marantz Forum. There may be an answer there.
 
I would try to get a thermistor from a donor unit.
It would be difficult to reverse engineer the specs from the original part.
We have little to go on as far as the thermistor specifications are concerned except the fact that it is 100Ω at 25°C. If someone had an SDT-100 thermistor and the equipment necessary to determine the B25/85 characteristics, perhaps an exact substitute could be found.

Tom
 
catrafter said:
I would try to get a thermistor from a donor unit.
It would be difficult to reverse engineer the specs from the original part.
We have little to go on as far as the thermistor specifications are concerned except the fact that it is 100Ω at 25°C. If someone had an SDT-100 thermistor and the equipment necessary to determine the B25/85 characteristics, perhaps an exact substitute could be found.

Tom
Click to expand...
Thanks Tom for replying before I even got a chance to check with you, I get the B25 part, (it’s actually a SDT-100 1k which I believe is 1000 ohm) 1K at 25 Celsius, but not sure of the 85 part. I know they are specified at different temp drops for each 1 degree, 3.9, 4.3, etc. I ordered several with my Mouser order last night, do you think if had an ohm meter on each one and heat them with a hair dryer I could see how they track in ohms as the temp increases it would be a fair way to determine a replacement? Or is there something I am missing?
Terry
 
You could boil a cup of water and measure the resistance of the thermistor at 100ºC or wait a bit and test at 85ºC, and keep track of the resistance while getting cool, both thermistors at the same time. If you see a close value, you could use them.

I don't know where it is used, but I don't think a circuit was designed around the accuracy of a thermistor.
 
elnaldo said:
You could boil a cup of water and measure the resistance of the thermistor at 100ºC or wait a bit and test at 85ºC, and keep track of the resistance while getting cool, both thermistors at the same time. If you see a close value, you could use them.

I don't know where it is used, but I don't think a circuit was designed around the accuracy of a thermistor.
Click to expand...
Perfect I will do that when they arrive,
Thanks
Terry
 
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