FAN0 inverted PWM?

Hey guys,
my Anycubic I3 Mega is acting a bit weird. A M106 S0 or M107 spins the fan up to 100% whereas M106 S255 makes it run at about 10%. There seems to be some kind of inverted PWM signal. It also won't turn off completely.

Could this be firmware related? I tried Marlin 1.1.9 and now 2.0 bet - makes no difference.
I tried to find something in the source code but couldn't find anything useful.

br st

Edited 1 time(s). Last edit at 07/21/2019 09:25AM by stan78.

It sounds like a defective mosfet, experiencing a Avalanche failure.
This is where the mosfet is partially shorted you will get full power and when the avalanche occurs you would get a crowbar effect giving you nothing or maybe the 10% fan.

The problem with a failure in this type is that, once it occurs, there is a high risk of a chain reaction which could disintegrate the MOSFET an probably blowing other devices to boot.
So it’s of extremely importance to test the mosfet for this defect and replace as necessary.

Using stranded mosfet tests

[electronicsbeliever.com]

[www.youtube.com]

---

Computer Programmer / Electronics Technician

Wow, you both did great. Stan for describing the effect really well by trying out the fan settings and Cliff by sharing this really good knowledge. Thanks, I'll try to remember this as well in case I ever come across an error like this.

---

http://www.marinusdebeer.nl/

Yeah, thank you very much for this detailed and probably correct information.
The Trigorilla boards seem to have very bad transistors for the fans. They break easily, allegedly.
On the i3 Mega there is a spare „heater 1“ port with pin D45 that is connected to a mosfet. So I put my fan0 cable to this port and changed the fan0 pin from 9 to 45 in the marlin source code.
Now the part cooling fan is behaving correctly again!

Hey guys,

I have a similar problem. The only difference is that my fan is not about 10% but around 60% when I turn in on completely (M106 S255).
Could you please tell me what exactly you changed in the marlin source software since I'm not sure what to change and I don't want to destroy anything.
Thank you for the help!

greetings

They had faulty MOSFETs, Ie hardware. Not marlin config.

Hello Dust,
Yes, I know. My mosfet is probably faulty as well but since I don't know how and which one to exchange l wanted to use the workaround stan78 described.

first you need to identify your controller.
From that you can work out what pins.h file it is using in marlin.
In the pins.h file you swap the pin numbers so that the fan0 pin is the desired port.
You recompile and upload.