LCD reading NOZ: def and BED: def

[Sextant]

I am just completing my build of the RMv2 and am at the stage of uploading firmware. The LCD is alive however the NOZ and BED temps are both reading def. Everything else displays similar to the description shown in the manual. The example in the build manual shows these values to be (presumably) ambient at whatever temperature the room is where the printer is.

When I loaded the firmware and the LCD came to life, it did flash temperature values that seem reasonable. However the flash only lasted about 2s

Q; is this an indicator of problems with both thermistors?
Is there a way to trouble shoot this without having to disassemble and re-do both thermistor locations?

[guanu]

typically one only has a problem... when you turn the machine on, during that 2 seconds the display shows before it goes to def, one of the two thermistors will show a funky value, ususallly -20 or something like that in a negitive, that would be your problem thermistor, typically happens on the hotend and a solder connection came loose... only other way it would show def is if the thermistors werent plugged into the proper spots on the board..

Guanu

[Sextant]

you are correct, the value of the hot end was -20. And after scrolling up the text in the Repetier window I did see that it was reporting that the hot end was defective. Using a magnifying glass and strong light I could see that the PTFE shield is not seated at the thermistor head and that a small amount of wire is showing.

Would the def signal be caused by the thermistor touching the body of the hot end somewhere inside the permatex?

[guanu]

it could be the 2 legs of the thermistor touching each other or the solder connection to the wires came loose... I've had to un-tape a couple hotends before to resolder the legs to the wires that came loose before...

Guanu

[Sextant]

Before I take the thermistor out of the hot end and after I un-tape and check the connections, is there a way to test to determine if the legs are touching inside the hot end hole inside the Permatex?

[Polygonhell]

Measure the resistance of the thermistor at room temperature, it should be in the 100KOhm range. The hotend should be in the 3-4 Ohm Range

[Sextant]

After removing the hot end and de-taping the wiring, I found that one lead was disconnected from the thermistor. The thermistor that came with the kit broke after several attempts at re-soldering. The thermistor that I have now, which is a replacement, reads 200K. How much of a problem will this be if/when I install it into the hot end? Can the controls be adjusted based on actual temperature readings (as from a laser temp reader)?

[Polygonhell]

Assuming it's a 200K thermistor you can adjust for it in the firmware.
Laser temperature guns are pretty much useless for setting up a hot end, you really need to use a thermocouple, the problem is the cheap ones read way to large an area to get an accurate reading with one.