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Fan does not turn off


peter_p
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Posted · Fan does not turn off

Since a few days my head fan does not turn off completely when switched off either by using the Ulticontroller or gcode M107.

Does anyone have an idea why?

Thank you in advance,

Peter

 

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    Posted · Fan does not turn off

    There is a chance the Darling transistor driving the fan has given up (the one right to the left of the stepper drivers, labeled "Q4 Driver"). if that is the case, you need to unsolder it, and put a new one in. (most likely you shortened the 2 fan leads while running, which usually means instant death for the transistor.)

     

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    Posted · Fan does not turn off

    Thank you, Joergen!

    I'll check the Darlington, although I think it was not due to a shortening. Also, the fan reacts on commands, speed up and down. The behaviour is more like an offset: zero isn't zero.

    Peter

     

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    Posted · Fan does not turn off

    Ulticontroller says correctly 1 or 0 when these commands are sent, but

    255 ~ 19V DC, fan runs at full speed

    0 ~ 4,4V DC, fan still runs (at low speed)

    The voltage is measured at the fan while it is connected, otherwise it is always ~19V (high ohmic).

    But I don't know if there is simply a DC voltage needed for the fan (?).

     

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    Posted · Fan does not turn off

    The fan is PWM driven, so at 255 you see 19V (a bit more than the nominal 12V it was made for), but at 0 you should see 0, so something else is whacked. (no idea, hopefully UM support can jump in here and help)

     

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    Posted · Fan does not turn off

    Anyway, have many thanks Joergen!

    Peter

     

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    Posted · Fan does not turn off

    At this point, I would re-run the first run wizard and install the Marlin firmware again. It could be a messed up instruction in the firmware which is off by one bit.

     

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    Posted · Fan does not turn off

    Yes Bill, but this was the first I did.

    Peter

     

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    Posted · Fan does not turn off

    Update: it was the Darlington transistor; the base was always around 4-5V even when turned off. The reason that the transistor died (or better, became sick) is perhaps due to the inductive load of the fan creating spikes. Anyway, I've replaced it plus added a diode between collector and emitter.

    Peter

     

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    Posted · Fan does not turn off

    With transistor the port outputs only 12V at 255. Only without transistor it's 19V.

     

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