I've recently purchased Anet A8. First print went well, but now, the hot end temperature stays at ~230 °C. When I touch it, it is still cold. I tried the thermistor, and it correctly changes resistance when I blow on it (from 100 kΩ to ~70 kΩ). The voltage in connector is about 300 mV.

Does anybody know what could be wrong?

  • $\begingroup$ Have you tried swapping the bed and extruder thermistors at the board? $\endgroup$ – tjb1 Sep 8 '17 at 11:05
  • $\begingroup$ I tried it. I fixed the problem, see my answer. $\endgroup$ – honza-kasik Sep 9 '17 at 14:35
  • $\begingroup$ Apologies for the previously botched edit. Poor eyesight :-) $\endgroup$ – Greenonline Jul 16 '18 at 21:55

In my case, I had a bad resistor on my board. R41 had only 2.2 kΩ instead of 4.7. I replaced it and everything works now.

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    $\begingroup$ Just out of interest, how did you know that the value of R41 was incorrect, and what the correct value should be? Did you deduce it from looking at a schematic, or comparing like components or by calculation? Or was it just a faulty resistor, that was the incorrect resistance when measured with a DMM? Was the incorrect part caused by a manufacturing or design error? $\endgroup$ – Greenonline Jul 16 '18 at 20:59
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    $\begingroup$ I measured it with Ohmmeter and compared the result against value written on it. I really don't know how resistor may become 'bad'. Shortening maybe? $\endgroup$ – honza-kasik Jul 19 '18 at 12:02
  • $\begingroup$ It could have been badly soldered and over heated when the board was made; damaged in the fabrication process of the resistor itself, or; just got old? :-) Note that care should be taken when measuring components when on the board, rather than in isolation, as other components in parallel can change the actual reading. $\endgroup$ – Greenonline Jul 19 '18 at 12:07

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