PD-Board Issue (Overcurrent/Overvoltage)
Hi,
before I recieved the PD-Board for my Upgrade from MK3s+ to MK4 I was struggeling with undervoltage for the 5V VCC (well known Issue)
Since I have the PD-board, the situation is vice-versa. At the final power up was everything ok, even the first prints. Then I switched the printer off and 20sec later I swiched on agian, the the printer restarted and showed the error that at the MMU port an overcurrent happend.
At this point, the message was persistant, so I removed mmu cable at the xBuddy > No Error. After reconnect, the error happens again.
I removed the connector of the MMU cable from printer at the PD - Board > no error, also no error happens if only the PD-Board is connected to the Printer.
Once the PD Board is connected with the MMU, then the error happens again. The Error also appeard if All stppers were disconnectd from the MM-Control Board.
I checekd if an unexpected low resistance (short circut) could be measured at the Input Connectors, but everything normal. (all min. 10k)
Then I stopped diagnostic and resumed one day later, and the Issue was gone... everything okay again.
Precautionary I also inspected the complete cable from Printer to MMU but couldn´t find any defects...
Some days later, the same behavior happens in the same situation, after successful print I powerd the printer down and back on >> Error MMU Overcurrent, persitantly, like at the last time.
This time I measured the 5Volts Supply at the disconnected PD Board at the socekt to the MMU. It was 5,78 Volts!! For my understanding more than 10% Overvoltage could be critical to some components...
Then I decided to power the MMU with an 5 Volt external power supply, like I did with MK3s and the undervoltage behavior.
Now everything is fine again, no error messages, everything is working.
@All, did anybody measured the 5 Volts output from PD board and observed an identical behavior?
Greets, Thorsten
RE: PD-Board Issue (Overcurrent/Overvoltage)
Hi Thorsten,
unfortunately we have exactly the same problem, after the upgrade to MK4. First prints were fine, but then it started with the overcurrent error. We checked all the connectors, cables and boards, everythings fine as it was before. We have smiliar voltage messurements.
So, can anybody help?
Greetings!
RE: PD-Board Issue (Overcurrent/Overvoltage)
We just took again messurements. At boot-up start, it,s 4.95 V and right before and during the MMU test it spikes up over 5.75 V. We assume that's the problem.
So, Prusa Team can you help?
Greetings!
RE: PD-Board Issue (Overcurrent/Overvoltage)
together with other people we are discussing the same bug on GitHub, a temporary solution is to leave the usb cable plugged into the MMU3 (no need to plug in the computer, just find a place to leave it be without obstructing the printing operations).
It’s not elegant but prevents the overcurrent creating a very very small delay in the MMU booting!
RE: PD-Board Issue (Overcurrent/Overvoltage)
Thanks for the Information @Pars3c, can you provide the link to the GitHub Issue?
And when I get this right, the Cable is just Plugged into the MMU, nothing else?
RE: PD-Board Issue (Overcurrent/Overvoltage)
RE: PD-Board Issue (Overcurrent/Overvoltage)
for me, I completely fixed that issue and having no more issues or other artifacts since that.
I added a 1Ohms, 1Watt resistor in every red wire (+24VDC) ( so the all over resistance is 0.5Ohms, cause the two red wires are parallely. )
that solution (current limiting resistor) is very common, don’t know, why Prusa didn’t done that for the 24v. For the 5V they did that solution.
current limiting resistors has a lot advantages, if calculated well, in normal condition the resistor has no impact, the voltage drop is here 0.1-0.2v (@24V)
In high current or error behavior that resistor helps to avoid other defects like burned semiconductors….
Greets Thorsten