SOS - The bed doesnt heat up - UM2

[shurik 87]

So, my 2.5 years old UM2 starts showing its age.

The topic title tells it all. The display shows the current temperature (26C) and that doesn't change.

No apparent damage, the device was staying all the time at the same place.

Where shall I start looking?

And all that when a few orders are waiting... Urgh!

Edited July 20, 2016 by Guest

[Dim3nsioneer 557]

At the connectors at the heater pcb. If they look ok, remove the thick lines and measure the resistance at the connectors. If you don't get any value, the pcb is broken. Next test would be if you get the voltage on the lines you just removed (just be careful with this).

If you don't get it running again and if you are printing PLA: take out a roll of blue painters tape and feel the glance of past days...

Edited July 20, 2016 by Guest

[swordriff 119]

Shurik, Privet!

Test elektrikal resistance (ohm) between the leads to the heat bed.

You can do that by loosening only one of them from the CPU board.

However, there is a 90% chance you only need to tighten the screws holding the cables from the bed to the CPU board. Use a small screw driver and tighten the crews..

[IRobertI 520]

It was somewhat common back then that the solder joints on the screw terminals were crap. So take a look at those and see if you need to re-flow them.

[shurik 87]

Thanks guys, I knew that despite the forum's design, you can be relied upon.

I put gluestick on the glass and continue with PLA prints (first time ever on a cold bed!), so far so good.

However, with deep embarrassment I have to say that my electrical skills and understanding are sub-zero.

I do not know what is pcb and how to test the electrical resistance. :( Not to say that no equipment for that exists in my house.

However, my hands are mostly at the right place, so if you could point me out (maybe, with some pictures or drawings?), I will try to find my way.

Cheers!

[shurik 87]

[neotko 1,417]

I would take out the heated bed (carefull it can bend) and look closely at the soldering points.

Ofc, first check that all the cables are on the board perfectly fit. Makes photos if you see something weird. Compare it to the um2 assembly manual. (It's on the github)

[shurik 87]

OK. Took out the heatbed. The cables look OK. Tightened the screws. Nothing.

Took out the main board, it looks fine. Checked the cables, tightened the screws. No effect.

Next step, I believe, should be checking the voltage/resistance on the main board contacts, right?

[IRobertI 520]

This image shamelessly stolen from Illuminarti: https://umgallery.ultimaker.com/uploads/gallery/album_27/gallery_341_27_479366.png

That image shows how to measure the temperature sensor on the board. The remaining terminals are for the resistive track on the PCB that heats up. That resistance should be about 3-4Ohms.

Also try measuring from the solder joint to the pin of the connector and see if there is continuity there. Like I said earlier, sometimes that solder joint is bad and it can be almost impossible to see with the naked eye. A small hairline crack can be enough to make it so that there is only intermittent contact between the connector and the board.

[shurik 87]

Happy end!

The soldering pointed by my red arrow below was slightly burnt out. Re-soldering fixed that.

Many thanks to everyone!