3D Printing Forum

Hi guys,
Although I do not write here much, I still read and enjoy the forum since the very beginning.
Right now, I'm stuck with my head in a dead wall (dead UM2 wall it is) and desperately need guidance.
Full description of the problem is here, on the UM forum. A few people there tried to help, especially neotko but it looks like they too run out of the ideas.
To make the long story short.
Recently, red wire of the printhead fans became loose, so I usually just pushed it back into place. But the last time, it somehow touched probably the other, black wire, causing a small spark and instantly completely killing the printer. The board does have all the normal voltage, but the display and the printer were totally dead.
I got another board, this time v2.1.4 (the old one was 2.1.1) from Aliexpress from a seller recommended by neotko and installed it yesterday.
Now the behavior is a bit "better". PC responds to the printer being powered up and connected via USB, and Cura 15.4 can successfully perform a custom firmware update, or so it says.
However, Cura 2.4 reports that it can't see the printer.
The printer itself makes a low noise upon being powered on, with Z motor doing some clicks, like it tries to start but just can't. If that Z motor is disconnected, then another one tries to do something similar. Aside the green light on the board, another yellow one blinks.
The display is dead and the printer won't come up.
The re are some photos and a video in the thread on the UM Forum, I can put them here, too, if needed.
Tried to disconnect almost each connector and start the printer, but with the same results. I'm desperate. Anyone?

The first things that come to my mind would be to check the stability of your power supply. Maybe it also got a "hit" from the short circuit. Check the power supply voltage with the board switched off and then continue measuring when the board comes up and does the homing operation. If the voltage drops, you might have a power supply issue - or the china board is an issue.
Next thing would be to try to upload a firmware from Arduino IDE and see if that gets it more stable.
I assume you have checked the end switches, fans, PTC and they all do not have abnormal values?

I hate to say it but I wonder about the quality of the replacement board from China, too.

LePaul wrote:I hate to say it but I wonder about the quality of the replacement board from China, too.

Nah it works. At least mine does

Thanks for posting!
I can't really do much diagnostics by myself, having only a standard multimeter at my disposal. This device shows correct voltages everywhere.
No Arduino around and since Cura did upload the firmware via "custom" mode, it should be OK, no?
The board looks OK. The printer responds already better with that new board. With the old one, the Z motor did not try to start and PC didn't react to the printer connection via USB.
And that amber or yellow blinking light on the board - what does that mean? Maybe, it's the clue?
Another thought - maybe, the display card needs replacement as well?
Clueless...