They shipped a special daughter board that should be used to connect data and motors to the MMU board and to the main board, and this should fix the issue. 

The MMU3, in addition to this daughter board has also a new set of cables,  but is still the same old electronic board and motors of the MMU2, with only the plastic parts and the firmware changed.
So who has not yet upgraded to the MMU3, I strongly suggest to do it, or get the board and cables and try to update the electronic parts of the MMU2.
Probably the delay were due to the pandemic period and to the time required to setup a production for the new tiny board. As you know PRUSA is now building al the electronic internally, so it could take a little more time than in the past.

I think the issue could be considered closed.

Regards

I also moved the blue wire from position 1 to position 4 (Not connected on my MMU board).

Posted by: @eoyilmaz

 

Posted by: @eoyilmaz

Just got the PD Board and, let me answer my own question here, it supplies 5.76V

Thanks for the info!

Posted by: @eoyilmaz

Did anyone measure the output of the new PD board? I'm not sure that I'm willing to spend £23 (AliExpress) for a board that possibly costs no more than £2 to make and keep my buck converter, but I at least want to match the output of the PD board.

Just got the PD Board and, let me answer my own question here, it supplies 5.76V

Posted by: @danaf

So I injected 5.5 volts on pin 1 as you guys suggest. I have 5.4 volts on one side of the diode and 5.1 on the other side, but no changes.  For me, in stuck with the idler that won't home. After upgrading the firmware, I first had a power error code, but it went away and this started. I was thinking the power issue was causing the idler home issue. 

I've owned this mmu now for several years and have never been able to get a successful print. 

I'd like to add however, that mine is hooked to an MK2.5S. 

no, the power issue causes the „all LEDs blinking“ error, the idle home problem after firmware upgrade is something different and can be solved by setting something by a gcode send directly to the MMU, there are different other threads addressing this. (My MMU runs on the old firmware and I will keep it that way…)

I've owned this mmu now for several years and have never been able to get a successful print. 

I'd like to add however, that mine is hooked to an MK2.5S. 

A decent picture may show the final circuit and how it connects to the second connector.  A Monday project I guess.