MMU3/MK4 wouldn't load all the way to extruder gear, now none of the motors are working
 
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MMU3/MK4 wouldn't load all the way to extruder gear, now none of the motors are working  

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ktpanda
(@ktpanda)
Active Member
MMU3/MK4 wouldn't load all the way to extruder gear, now none of the motors are working

Things went from bad to worse. At first, it seemed to be working - it could load filaments to the FINDA, cut the filament, etc. However, it could not load filament all the way to the extruder gears. It would stop just a hair short of the nextruder gear being able to grab it, so it wouldn't load all the way to the nozzle. It could unload the filament just fine.

I tried adjusting the idler tension, but while going through that process, I was trying the Loading Test from the Calibration menu, when it jammed and I had to reset the printer. After that, none of the motors will move. The lights blink on startup but it doesn't go through the homing.

I suspected the jam might have popped a fuse, but I probed what I assume are the fuses (the green components on the lower right of the board where the Buddy interface plugs in), and one of them reads 23.9V on both sides and the other reads 5V on both sides. I suppose it could have damaged the motor drivers themselves but I don't know how that could have affected all 3 motors.

Are there any low-level troubleshooting steps I could do?

Posted : 17/06/2024 10:08 pm
JoanTabb
(@joantabb)
Veteran Member Moderator
RE: MMU3/MK4 wouldn't load all the way to extruder gear, now none of the motors are working

Have you reset the idler tension again? too tight will stop it rotating

iirc the idler drum is the first stage of MMU3 startup.

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Posted : 17/06/2024 10:14 pm
ktpanda
(@ktpanda)
Active Member
Topic starter answered:
RE: MMU3/MK4 wouldn't load all the way to extruder gear, now none of the motors are working

I've loosened it all the way to pull the filaments out, and I can freely rotate the idler when it is off.

Posted : 17/06/2024 10:24 pm
ktpanda
(@ktpanda)
Active Member
Topic starter answered:
RE:

Here's what the LEDs do on startup:

 

I also probed the capacitors right above the motor driver chips and all 3 are getting 23-24V. All of the pins going to all motors are stuck at 24V and never go low (at least as far as I can tell with a multimeter, I don't have an oscilloscope)

This post was modified 1 month ago 3 times by ktpanda
Posted : 17/06/2024 10:33 pm
JoanTabb
(@joantabb)
Veteran Member Moderator
RE: MMU3/MK4 wouldn't load all the way to extruder gear, now none of the motors are working

Have you spoken to Prusa Chat. 
Might be worth pointing to this post

regards Joan

 

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Posted : 17/06/2024 10:51 pm
ktpanda
(@ktpanda)
Active Member
Topic starter answered:
RE: MMU3/MK4 wouldn't load all the way to extruder gear, now none of the motors are working

Ok, I figured out what it's trying to do by reading the startup sequence in the firmware. Turns out that I had a piece of filament stuck in the FINDA, so it didn't move any of the motors. I pulled it out and it's back to the original problem - it loads just short of the Nextruder gear and won't actually load.

 

 

Posted : 17/06/2024 11:00 pm
JoanTabb
(@joantabb)
Veteran Member Moderator
RE: MMU3/MK4 wouldn't load all the way to extruder gear, now none of the motors are working

Can you try a shorter PTFE Tube? 
Do you have a spare?

 

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Posted : 17/06/2024 11:31 pm
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