P802M temperature failure x2

Hi Folks,

it's happened again...

Symptoms.

See the attached image - the error message displayed is..

def / 190oC def / 50oC

System starts, preheat PLA, level the bed manually, load filament, print file from SD card.

at some point the error occurs and the temperature is no longer controlled, so the bed and extruder stop heating and the extruder stops feeding.

the head keeps moving.

first time I replaced the entire extruder head - seemed to fix it - but doesn't explain why the heat bed also stopped.


second time, I have no spares...


thoughts - is it really the heater head assembly? or is it the control board??? or a software bug?

Hi bulwynkl,

the error displayed is typical of a thermistor failure. Neither the bed or the extruder will heat since the system is unable to detect the temperature of one of them.

If changing the hot end solved it last time, then it may well be the extruder thermistor. If you have a resistance measuring voltmeter then (with the machine switched off) unplug the extruder and hot bed thermistors from the control board. Measure the readings across them, they should give a reading about 100kohm. If one or the other reads open circuit then you have found the problem. Also try to check the continuity of the wires from one end to the other, it may be a broken wire rather than a thermistor failure. In the case of the hot bed thermistor also check the continuity of the connecting tracks on the underside of the bed, plus look for dry joints in the soldering.

Supermec