MMU2S all red and green LEDs are always turned on  

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Nullzero
(@nullzero)
Trusted Member

I upgraded my MK3 to MK3S/MMU2S over the weekend, and I think I got it right.

But I'm having a problem with the MMU2S not working correctly.

When I power on the machine, the MK3S portion boots up fine. I can calibrate, move the axis around, use the hotend etc.
However, the MMU2S is unresponsive. All red and green LED lights are turned on (but not blinking). I can press or hold the buttons, but nothing happens.

Things I have tried:
- flashing the firmware on the MMU2S multiple times. It's successful every time.
- adjusting and tightening the screws inside the eletronics box, that have the power cables connected. No change in behavior.
- checking the power connect to the MMU2S board. The cable is correctly seated on the board.
- Oddly, if I press the reset button on the MK3S, the MMU2S resets, and the right-most green LED is weakly blinking. But the result is the same, with unresponsive button presses.

Another strange phenomenon: if I plug the MMU2S into my PC via the USB cable, it starts working. The LEDs change from red/green to a single green LED, and I can use the buttons to move the selector head. I can tell the MMU2S to load filament. But as soon as I unplug the USB cable from my PC, the MMU2S goes into a zombie state again... and is unresponsive.

Is this a power problem, perhaps? Maybe the MMU2S control board is not getting enough voltage or something? But the USB gives it plenty of power? I am in Japan, so the mains voltage is only 100V from the wall socket. Could that be a problem?

I also have a very early MK3 machine. One of the first pre-orders, I'm sure. Could the electronics be different some how?

Thank you.

Posted : 08/04/2019 1:59 pm
DomS
 doms
(@doms)
New Member

I was having this problem today, I spent ages trying to figure it out!

Eventually I tried taking all the wires out and putting them back in, what I noticed was that i had put my signal cable all the way to the left in its area. but i noticed in their picture they have a little spacer that shifts it one pin to the right. I moved it to the right and the mmu2s suddenly came to life. Not sure if its the same problem for you but that fixed mine.

Posted : 09/04/2019 6:27 pm
Nullzero
(@nullzero)
Trusted Member


I was having this problem today, I spent ages trying to figure it out!

Eventually I tried taking all the wires out and putting them back in, what I noticed was that i had put my signal cable all the way to the left in its area. but i noticed in their picture they have a little spacer that shifts it one pin to the right. I moved it to the right and the mmu2s suddenly came to life. Not sure if its the same problem for you but that fixed mine.

Wow, thank you so much! This was EXACTLY my problem!

My Einsy board doesn't have this orange buffer. So I was plugging my signal cable one peg too far to the left! I shifted it one over, and now the MMU2S appears to be working! Woot!

Posted : 09/04/2019 10:58 pm
CybrSage liked
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