Geeetech

Hey, thanks for your reply.
I noticed the wrong documentation after i took the multimeter to measure the pins. I connected the fan like you said.
But the voltage of the pins never got to 0V its even between 3 and 6V so i can control the an but i cant stop the fan.
This seems not to be the sense of an pmw port. Can you control your fan?

But thanks for your efforts, i took me a bit of time to notice the wrong documentation

Hi Stuiven

I had a little problem with my damn 1$ fan ! ☹
One badly welded wire came off and caused a short circuit.
The MOSFET on the GT2560 has had a nasty heat stroke and it behaves differently now:
- M106 S0 (fan stop) gives now a nearly 10v output voltage
- M106 S255 (maximum speed), the voltage drops to around 3v
- when S value increases, the voltage decreases
The curve has reversed, and covers now a smaller range (3 to 10 instead of 0 to 12)

I do not have the skill to change this SMD component on the board.

As workaround while waiting for a solution, I modified the firmware, in Marlin_main.cpp for the M106 commands:
// ppf: the MOSFET blows up ! If 255 the fan turns to mini, if 0 it turns to max ==> reversed
// if (p <FAN_COUNT) fanSpeeds [p] = s;
If (p <FAN_COUNT) fanSpeeds [p] = 255-s;
And for M107 command:
// ppf: the MOSFET blows up ! If 255 the fan turns to mini, if 0 it turns to max ==> reversed
// if (p <FAN_COUNT) fanSpeeds [p] = 0;
If (p <FAN_COUNT) fanSpeeds [p] = 255;

It works more or less as expected:
- at lowest speed (M106 S0 and M107) : the fan (a new one) rotates slowly
- at max. (M106 S255): it turns almost to the maximum

When I will have finished other more important tasks, I will try to solve this with an Attiny45 micro controller that will read this voltage from 3v to 10v and will regenerate a proportional 0-12v range PWM signal to a new MOSFET (one in a TO-220 package ).
And as a bonus, I will also try to solve in the code of the Attiny45 the problems for the small vibrations and for the lazy startup within the small speeds range.

I connected the Fan to the PWM Connector. two wire to yellow and ground Pin. It's not working, I tried slicer settings, direct switching in Octoprint and M commands... nothing works. Do I have to set it up in Marlin? Or do I have a Faulti Board. The fan is running correctly on the Fan connectors.

Hi,

I did some measurements and it appears to be that the voltage between those 2 pins is always 0, no matter what the fan speed is set. I have connected LEDs via another MOSFET module and they are always on. Do I have a faulty MOSFET? If yes, what can I do?

Here is some more information:
I use LED strips with built in resistors. They operate on 12. I supply them with the power supply. I use IRF520 mosfet break out board to control LED stripes with PWM from PWM_FAN port. I was worried that the current from for the LEDs might be too high for the port. IRF520 was a safer choice. However, I was unable to get any control on the voltage output from the PWM_FAN port. It is always 12V no matter what is set. I tried both LCD panel and gcode (M106 Snnn).

Thanks!

You can replace it(STP55NF06) with a new one

Hi William, I think it is an AP2302AGN. At least according to the schematics and the way it looks like. It will be a tough soldering for me.

Since yesterday, same problem here. Been running the GT2560 for a few months and now suddenly the PWM fan keeps running (although at a low-ish speed)

I can make it run faster with the M106 command but can not shut it down (naither M106 S0 or M107)

New mosfet ? Or new board ?

Might look for a different board alltogether as, although I like the GT, I don't like the mini connectors, they're horrible in my opinion.

The MOSFET(3 pieces) on the GT2560 is used to control the nozzle and heat bed heating

Yes, but the PWM_FAN is controlled by another MOSFET. I think that is the issue. Or the AtMega2560 has an issue with it's PWM. Is that possible? In that case, board needs to be replaced. Right?

Replacing the PWM mosfet fixed the issue... wonder if it's voltage rating is high enough. I saw some replacement being 20v..... I used a 30v one as replacement.