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While this may seem like terribly noobish question, I'm sure one day someone will have same problem.

I own a ZONESTAR P802QSU (Bowden extruder) and all of sudden my extruder motor stopped working. What I did:

  1. I check whether or not motor is moving freely - I can rotate it without any problems manually.
  2. I checked out cable and plugs - everything seems OK.
  3. I checked whether motor is working after plugging it into another slot in motherboard - motor works fine.
  4. I checked if another motor works after plugging it into same slot on mainboard - and it does not.

It would seem that there is something wrong with E0-mot driver module, or with socket. I'm however totally at loss about what can I do with any of those. I do not have any electronic equipment except multimeter, and voltage on motor seems fine(11.3V between red and black, I guess V+ and ground). It sometimes seemed to get lower, but I'm almost sure it is my trembling hands.

After some googling, I started checking A4988 stepper driver with my multimeter. VDD was ~5V and VMOT around 12V, so it seems to work at least in this way.

What can I do, to see what is broken? Visually nothing looks like it burned out, but I'm fully aware it may not be visible.

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    $\begingroup$ what is the nozzle temperature when you are checking the motor? there is a build protection to avoid cold extrusion $\endgroup$
    – profesor79
    May 4 '18 at 11:11
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    $\begingroup$ This is a valid point. I performed similar troubleshooting on an extruder motor with similar results until the thermal protection aspect was pointed out to me. Perform your tests again with the nozzle at operational temperature before you replace parts. $\endgroup$
    – fred_dot_u
    May 4 '18 at 15:18
  • $\begingroup$ I co drukujesz juz? $\endgroup$
    – profesor79
    May 4 '18 at 21:29
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    $\begingroup$ Tak drukuję/ Yes, I'm prinitng again after chaning stepper driver to spare one - but I'm almost sure it is the case. It's in midle of really long printing right now, so I can't check it. I gave you upvote, and will check it tomorrow before accepting. $\endgroup$ May 5 '18 at 16:07
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As this is not an obvious case, most printers' firmware has a cold extrusion prevention. That is usually set at 170C, so the nozzle need to be over 170 to allow stepper to move. I experienced that when I was assembling my TT and doing a cold run, to validate all mechanical movements and clearance.

In Marlin firmware, the extruder stepper is switched off after extrusion, so we can freely move it, but not other motors and that could give us a thought that something is bad with the driver.

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  • $\begingroup$ It actually works like that in Zonestar P802QSU as well. I guess it was the case! $\endgroup$ May 6 '18 at 14:37
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Good investigation there! You are almost certainly correct that a driver chip has gone blooey. Personally I doubt it's worth the effort to locate and repair, rather than buying a new, trustworthy board.

I recommend this approach because one blown chip may well have caused (or been caused by) unrecognized damage elsewhere, which might then lead to future failures.

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