Broken Thermistor?

[analog_banana]

I can't heat my hot end up today..
Repetier is reporting the hot end temperature as -20 something degrees..
That would be a broken thermistor most likely?

Does anyone know a way to test a thermistor?

I have a "J-head" on it's way to me, so at least I have an alternative, but I will need a way to mount it on the rostock max.

[Woolf]

measure the thermistor with an ohmmeters, but when Repetier shows -20° then I think that the thermistor is really broken. Have you another Thermistor to test it?

look this, How i mount my J-Head http://forum.seemecnc.com/viewtopic.php ... 0&start=10" onclick="window.open(this.href);return false;

[analog_banana]

Thanks - I tested the resistance.
the bed thermistor measures a healthy 100k
the hotend thermistor measures 1.9meg??
To the bin it goes!!

Failed components so far:

PSU - faulty batch
Extruder - orginal replaced by vendor on his advice.
Bowden Tube: mechanical faliure
Thermistor - failed - blown??

It was really lucky I happened to order a Jhead this morning on a total whim,
so I will have a spare thermistor soon.

[Jimustanguitar]

-20 is possible... Remember that zero doesn't mean zero **edit... I meant that a thermistor could theoretically report that temp, not that you live in a freezer!

Probably a damaged thermistor or loose wire/connection though.

[Eaglezsoar]

I can't heat my hot end up today..
Repetier is reporting the hot end temperature as -20 something degrees..
That would be a broken thermistor most likely?

Does anyone know a way to test a thermistor?

I have a "J-head" on it's way to me, so at least I have an alternative, but I will need a way to mount it on the rostock max.

There are several mounts on Thingiverse, just do a search while on Thingiverse for jhead mount rostock

[analog_banana]

Thanks Jim,
As far as I know I've been measuring in Centigrade and looking at centigrade in Repetier.
Even accounting for the temperate British Climate, -20 is a bit outside standard room temp. range.
Especially when the bed reports +22

I checked the thermistor at the business end - the actual thermistor wire pigtails -
It's giving a really wierd resistance measurement compared to the bed thermistor.
I don't trust it!

[analog_banana]

Thanks Eaglez.
Printing upgrade parts is not an option for me right now.
I've never really had much luck printing anything except test cubes, and right now I can't even extrude.
But maybe I can find someone local to print one for me..

For now I will just try and get a working thermistor in the old hotend.