I found serious design error in MMU2 electronics hardware  

RE: I found serious design error in MMU2 electronics hardware

I believe that the proposed mmu2s modifications have been covered within this thread, 

I Would welcome a comprehensive, step by step how to... for those people who are not planning to upgrade to MMU3, and who are comfortable modifying their MMU2S, that will have to be a community  development as I doubt Prusa will go down that route

there may be scope for people who wish to retain their MMU2S, to print the MMU3 plastics and gain some of the advantages of the prusa development.

A new thread for the proposed SKR option would keep this thread more focused on the MMU2 with the Prusa board. 

there have already been community mmu2  firmware releases, I tried one, a long time ago. if I recall correctly that was for the MMU2 with Mk3, not the MMU2S with Mk3s

many folk have got the MMU2S to work, without revising the power supply. 

changing the circuit on the mmu2 controller is something that many folk will not be comfortable with. 

I have no idea whether the community  modified MMU2 will work with the latest MMU3 firmware that is something that I expect the members following this thread will try, once the MMU3 firmware is released. if it doesn't then people who retain the community modified  mmu2 may miss out on future developments by prusa. 
I believe  Mk3s and mk3s+ can work with the MMU3. if this is correct then the assertion that you need to upgrade to mk3.5 is incorrect. 

regards Joan

RE: I found serious design error in MMU2 electronics hardware

your post sounds a tad jaundiced. The post mainly concerns an electronics issue with the MMU2, for which two solutions have been canvassed, one short term, the other long term. Users can choose to deploy either or both solutions, but other than saying “me too” little purpose seems to be served by continual growling over the same single issue. Now it seems you want to turn this into a campaign for justice from Prusa towards people that purchased the product. Prusa (it seems) have addressed the issue by incorporating “improved electronics” into the design of new model “mmu3”. So this  appears to be a third pathway to resolving the issue, and its accessible to all having the skill to assemble an MMU but not necessarily having electronics expertise.

But a campaign such as you have canvassed is not the topic of this thread. You are of course welcome to open a new thread. The title I guess might be something like “MMU3 should be a free upgrade for owners of MMU2”. See how far you get, I wish you luck.

RE:

I do not get what's the fuzz about... This thread addresses a known electronic issue with the MMU2, which in my case developed with time. My MMU2 worked nicely with only some mechanical mods (like the pass through adaptor and bigger PTFE tubes). After many months of operation the strange all lights flashing error appeared with increasing frequency. Perhaps because auf aging components, changing currents and resistance - I do not know. I got it fixed with the help of this thread (converter power supply).

Point being: This thread might still be very helpful for people with working MMU2 if they encounter the same issue somewhere down the road.

So let's keep this thread covering the issue and possible solutions and let's discuss upgrade options, and what we will miss if we keep the MMU2 (I certainly will) somewhere else...

RE: I found serious design error in MMU2 electronics hardware

As a fellow Robin, I agree that this thread is important.  I have an MMU2 kit, still in it's box that I purchased with the MK3s+ printer in March as my first printer.  I am about to assemble it now and planning on doing all the mods that I see seem to work as posted by users.  The power supply issue sounds logical and will look through this thread more on the issue.  Will modify the board or add the external supply as required.  I have read enough posts from people that have had working MMU2s for a long time and don't see a need to upgrade at this time.  In the past 4 months, I have learned for my needs, I will need multi-head printing and will get/build a mutli-head system for my next printer.  Right now, multi-colour is what I want to get working.

RE: I found serious design error in MMU2 electronics hardware

@heine-mau - Thank you for finding and reporting this issue! My MK3/MMU2 had almost become entirely unusable! I could barely even get it to load filament for single color prints. It has now finished 2 - 17 hour long MMU prints without issue.  I used a LM2596 converter, dialed in to 5.2v like @fissi0n & @krzysztof-kaczor demonstrated. 

I am disappointed that Prusa hasn't been more proactive on this issue. I am always hyping up how open, and active Prusa is, and this one feels like the ball got dropped. And I don't consider the MK4/MMU3 upgrades to be a solution. As those upgrade kits have not yet started shipping, and the MMU3 can ot even be ordered at this time. Sitting this machine on the side, and waiting isn't an option.

RE: I found serious design error in MMU2 electronics hardware

Posted by: @hackmonkey-2

I am disappointed that Prusa hasn't been more proactive on this issue.

True. The way PR takes care of MMU2 doesn't give me any confidence to buy the upgrade to MMU3. Our community provided a lot of feedback and also implementations for many of the most common issues. And it feels like none of them made it into the main branch. That's why it's very important to keep such threads open and alive so the owners can at least prolong the live of their existing units.

RE: I found serious design error in MMU2 electronics hardware

@hackmonkey-2

I find the first part of your post to be very helpful and true to the spirit of the topic. For physical reasons, I have not assembled my MMU2S because it is difficult to manipulate small parts and I can 't "tinker" with it.  The early posts gave me hope, and the feedback from people like you, have convinced me to invest the time and energy to build it with confidence that I will have a working MMU2S. People like @heine-mau. the people who made valuable on topic posts, and no less importantly, people like you that posted what you did and the results, have made/will make MMU2S printing a much more enjoyable 3D printing experience.

PS: I will definitely post my results. My initial plan is to use the original kit parts, a LM2596, and maybe an inline power switch.

Kenn

RE:

Having these power issues myself now.

trying to get the correct voltage. 4.71v after D1 is what I’m testing now. Making my first test print now

PIC IS REVERSED! 5.2V injected

RE: I found serious design error in MMU2 electronics hardware

Good news, the new FW 3.0.0 works with this modification. Seems even more reliable now. Anyone else wanna chime in?

RE: I found serious design error in MMU2 electronics hardware

This is a massively helpful thread and definitely identifies the problem I'm starting to have with my 2 MMU2 units (Constant rebooting for seemingly no reason), I have ordered up some Deoxit and will clean up my stepper motor contacts on the MMU board and on the connectors from the motors themselves. I'm not a deep electronics guy (I can build a printer, but not snap-wire it) I'm comfortable with simple soldering and definitely want to resolve this issue, but I'd love to have some form of "How To" step by step process to try it out. Does anyone have the wherewithal do do that? Heck, if bypassing a diode is the simplest solution, I'd be down for that, I just need s nice picture with an arrow and some idea on how to do it. 

Thanks to everyone here for all the work in tracking this down, I appreciate any help I can get to get this fixed on my end..

RE:

I just need s nice picture with an arrow

MMU D1 diode shorting (source MMU Board Git):

RE: I found serious design error in MMU2 electronics hardware

Thanks! Just verifying, you're just jumping over the diode pins with a short length of wire? Is there something coming off the jumper down into those clips below?

RE: I found serious design error in MMU2 electronics hardware

What I did was not jump the diode and just injected the 5.2v. It’s completely reversible and easier to do. It works completely. I was thinking about making a video on doing it. Just dealing with a tooth infection right now. But it easy enough to explain / take pictures on how to do it. You need wire,soldering stuff, ac to ac buck converter.

RE: I found serious design error in MMU2 electronics hardware

Ac to ac?

Joan

RE: I found serious design error in MMU2 electronics hardware

Posted by: @realityfoundry

Thanks! Just verifying, you're just jumping over the diode pins with a short length of wire? Is there something coming off the jumper down into those clips below?

Just „jump” the diode so no more voltage drop.

nothing coming off.

RE: I found serious design error in MMU2 electronics hardware

sorry, DC to DC buck converter. Take the 12V DC from board input and inject 5.2v to “Blue wire” input. Blue wire has to be disconnected from board. Which I just pull the pin from the connector so no damage is done. 

RE: I found serious design error in MMU2 electronics hardware

I think there are many ways to solve this, with none of them being necessarily 'more right' than the others.

If it works for you, and it follows safe and accepted practice, then do it.

RE: I found serious design error in MMU2 electronics hardware

As we know now, Prusa has "confirmed" the Power Delivery Issue with it's release of the MMU3.

The thing is: I wanted a working MMU2, back when I bought it (had only troubles with it, but was afraid to destroy something, by soldering, etc.).
And I'm sure, I'm not the only customer...

Will Prusa send us the PD-Module for free?
I'm not really willing to pay another 100 eur for the mmu2->mmu3 upgrade.

I've already done mmu2 -> mmu2s upgrade back than... but this didn't solve the problem with the 5V.... 🙁 

RE: I found serious design error in MMU2 electronics hardware

After a few weeks of lurking on this thread, I finally pulled the trigger on the buck converter fix and can confirm that fixed the issue on my REV 0.4.4 board. I’ve been having intermittent light errors and eventually hit a wall prior where my steppers barely moved. Ever since I installed a buck converter, it’s been perfect. I'm also running the latest 3.0 firmware, no issues there as well.

For anyone looking into this solution, this thread is the best immediate fix, I doubt it’ll officially be addressed outside of the MMU2S to MMU3 upgrade which will no doubt take ages to stock and ship. I didn’t want the MMU2S to sit around and take up space so I opted to do this fix, it’s a bit disappointing to have to go this far but fortunate at the same time there are resources like this thread to help provide insight to those with less knowledge to detect and remediate this type of issue like me.

RE: I found serious design error in MMU2 electronics hardware

In prusa blog post if they carnt get it working with you through live chat they will send free upgrade kit till end of year