Thermistor substitution - Marantz 4070

[quadmatrix82]

Hi all does anyone know a new substitute for thermistor td-a135 fitted to a Marantz 4070 location h719? Thankyou!

 

[petehall347]

mt-350

 

[quadmatrix82]

mt-350

Thankyou do you know where these are available to buy?

 

[petehall347]

sorry i can't find anything yet

 

[petehall347]

i do believe its an NTC type thermistor . you could look closely at it for any writing on it ..
plus you could try measuring another good one at different temperatures then try to match it with whatever is available .
basic resistance at 25c first .

 

[petehall347]

just seen this thread strangely enough .. https://audiokarma.org/forums/index.php?threads/kr-4070-question.983736/#post-15321950

 

[quadmatrix82]

i do believe its an NTC type thermistor . you could look closely at it for any writing on it ..
plus you could try measuring another good one at different temperatures then try to match it with whatever is available .
basic resistance at 25c first .

Ok I will have a look I don’t think anything written on it and nothing comes up with the part number listed in the schematic

 

[quadmatrix82]

The

i do believe its an NTC type thermistor . you could look closely at it for any writing on it ..
plus you could try measuring another good one at different temperatures then try to match it with whatever is available .
basic resistance at 25c first .

They measure in circuit approx 150ohms

 

[quadmatrix82]

Maybe something like this would be ok?

https://au.mouser.com/ProductDetail...GAEpiMZZMv1TUPJeFpwbkxJGpkuv3W9%2BYn/xEDYQBk=

 

[petehall347]

you have to remove to test .

 

[quadmatrix82]

you have to remove to test .

Ok I removed from circuit looks like 336 ohm

 

[quadmatrix82]

you have to remove to test .

Do you think this would be ok?

https://www.mouser.com/ProductDetail/EPCOS-TDK/B57164K0331J000?qs=E/3ZYvLbbh86OUOsPmAYaQ==

 

[petehall347]

best to check datasheet then compare the curve to a good one .

 

[quadmatrix82]

best to check datasheet then compare the curve to a good one .

I can’t find anything on it when I google the part number hence trying to find a substitute

 

[quadmatrix82]

just seen this thread strangely enough .. https://audiokarma.org/forums/index.php?threads/kr-4070-question.983736/#post-15321950

Had a read makes me think whether if I need a ntc or ptc thermistor- does anyone know the characteristics of this thermistor?

 

[petehall347]

whilst testing it warm it up and if the ohms goes down its NTC if it goes up its PTC .
data sheets show an initial reading at 25c . then show a graph .. all you have to do with a good one is find one with the same initial reading then look at the graph and see if your good tests the same as the datasheet

 

[quadmatrix82]

whilst testing it warm it up and if the ohms goes down its NTC if it goes up its PTC .
data sheets show an initial reading at 25c . then show a graph .. all you have to do with a good one is find one with the same initial reading then look at the graph and see if your good tests the same as the datasheet

Thanks for your help I just measured it and temp goes down when I hold it in my fingers so you’re right it’s a ntc

 

[quadmatrix82]

I k

whilst testing it warm it up and if the ohms goes down its NTC if it goes up its PTC .
data sheets show an initial reading at 25c . then show a graph .. all you have to do with a good one is find one with the same initial reading then look at the graph and see if your good tests the same as the datasheet

I got a temperature sensor at approx 24.5 degrees I get 350 ohms I can’t find a data sheet on the original so you are saying I need to find a 350 ohm ntc thermistor?

 

[petehall347]

yes find 350 ohm one . then look at its datasheet .

 

[quadmatrix82]

yes find 350 ohm one . then look at its datasheet .

I’ll look around I found 330 and 390 ohms only so far might get them both and see how they go thanks for your help