Fan does not turn off

[peter_p 0]

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

 

[joergen 2]

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.)

 

[peter_p 0]

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

 

[joergen 2]

if the fan still reacts to commands, the transistor is just fine... zero not being zero is strange. how fast is it going with M106 S1 or M106 S0?

 

[peter_p 0]

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 (?).

 

[joergen 2]

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)

 

[peter_p 0]

Anyway, have many thanks Joergen!

Peter

 

[billdempsey 0]

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.

 

[peter_p 0]

Yes Bill, but this was the first I did.

Peter

 

[peter_p 0]

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

 

[cora111 0]

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