nasty problem after crash due to short circuit

[studiogijs 0]

I just experienced a crash. The printer halted and the power was completely down. I had to unplug the power adapter to get it back to life. After little investigation, it seems that I have caused a short at the fan on top. I was testing different fan combinations yesterday and had not noticed there was a little strand of the wires in the open after reconnecting the molex connector. Due to the movement of the printer I guess it has caused an unlucky short circuit.

But now, when I plug in the 19V power, the top fan starts blowing, and does not react anymore to M106 or M107 command. In other words: have I damaged the PWM connection of this fan?

For the rest the printer seems to be working well.

How can this be repaired?

cheers,

Gijs

[joergen 2]

Yes, I had a similar accident: You most likely fried the BD679 darlington transistor (PWM for the hot end cooling fan)... easy to replace, it's the one just left of the group of 3 stepper drivers: http://reprap.org/wiki/Ultimaker's_v1.5.4_PCB#Version_1.5.4_of_the_electronics

[studiogijs 0]

Thanks,

just saw your reply on google groups. I will unsolder and give it a test!

cheers,

Gijs

[echofabteam 0]

Hello,

We had a similar problem at the lab with the Darlington. We replaced it twice and also changed the power supply as we Asuspected it was the source of the problem. As we also suspected a short in the wiring from the printhead to the board, we replaced it.

Now what could cause that kind of problem? I'm mesmerized by that.

The last time I did a test after replacing the darlington, I noticed that the extruder missed some steps before the problem. It very rarely happened before.

Any help appreciated!

Cheers,

Marc-O

[echofabteam 0]

Update:

So I replaced the Darlington again, installed a contraption allowing me to replace it easily without soldering which is great. I found that the source of the problem was a bad polulu which would explain the skipping steps and extruder problems.

After testing printing for an hour or so, it crashed again. Missing steps and fan stopped working. The BD679 again.

Would someone have a solution or idea about what's going on?

We have been using the ultimaker since march with some success.

The machine has been tweaked due to some major problems with copper bushings and some mechanical problems but nothing that may cause this problem.

[Daid 306]

Maybe there is something wrong with the fan, causing it to draw too much current and thus blowing the darlington?

[echofabteam 0]

We replaced the fan but the situation occured again.

So we thought the resitance in line with the darlington might not be enough. Althoug this situation would happen more often wouldn't it?

By any chance, is there anything I should check in the firmware that might cause the problem? There's seem to be a link between the polulu that died and our fan problem.

Thanks for your help!

Marco