3.1 Suddenly 4028 Loses PWM control
Hello everyone, I have not used my printer in awhile, and Monday when I turn it on I realise my cooling fan has lost PWM control.
I ordered a new replacement fan but at 24Vs and this also had the same issue. No PWM control.
Measuring the PWM wire to ground shows range of between 0-6-12Vs going from 0-50-100% respectively.
I even changed the pin on my control board, but no dice.
My printer was working fine for months and there was no change in my CFG between it working and not.
I’ve spent all morning searching through previous posts and documentation to try find a solution but I’m at an end here.
Solution:Jump to solution
Problem was a shorted MCU, explains the sudden failure after working for 1.5 years.
Replaced the MCU and the fan (just in case the PWM module was damaged) and now everything works fine 👍...
16 Replies
Just going to bump this as it’s completely stumped me, anyone have any ideas?
Is the fan running 100%?
can you share your config and what your have wired to where?
Yes, it was never a problem before, worked fine for a year until I didn’t use it for a month
Sure no problem
I remapped the PWM pin to !PD13 to see if it was a problem with the normal Fan Header. Same result
Measuring the voltage across the PWM and the fans GND at different fan % in klipper shows:
100% 22V
50% 10V
0% 0.6V
The voltage across Fans Positive and GND is 10.8V
if im not mistaken, the pwm signal should not be varing voltage correct?
If you're measuring it with a multimeter it will look like a varying voltabe. You would need a scope to see the actual pulses
I am pretty sure pwm singnal is always 3.3v or 5v based. Are you measuring the negative ping on the port you are using for PWM?
That’s what I thought, in the video you can see I have the GND positive and PWM going to the fan exposed for probing
Haha maybe I should get one 😂😅
Didnt see the video. That is strange. Normally I think you are supposed to remove the voltage select jumper on the port you use for PWM but thats just a safety thing so you do not accidently run voltage to the PWM pin. If I get time later today I can try using a voltmeter to see what I see on my PWM pin as I have never done that.
Did you ever find the time to see what the voltage was?
I ordered a new fan direct from ratrig and some new cable. There are no continuity issues however I want to be sure
Do you also think it could be software related?
software? no. Configuration of that software? sure. I'd be triple checking the pins you're using
We have been tied up at the house. I am just heading out for the day. If you can remind me tomorrow, I’ll happily check for you as I am curious as well. What I would say is don’t plug anything else into it until we understand as software or configuration would not show high voltage like that but a MCU hardware problem could and cook a new fan.
Ok thank you! You really didn’t have to do that so I greatly appreciate it. I have a spear MCU so if your voltages are a lot lower then I will assume something is wrong with mine and I will install a new MCU
Solution
Problem was a shorted MCU, explains the sudden failure after working for 1.5 years.
Replaced the MCU and the fan (just in case the PWM module was damaged) and now everything works fine 👍