Print head fan is dead

[czucker 0]

So, my print head fans aren't working. I've tested them on another power supply and they run fine.

I've poked around the forums and it seems likely that I may have blown out the darlington transistor.

Unfortunately I'm not very good with a multimeter. Can anyone tell me what Ishould be measuring/looking for?

 

[czucker 0]

Problem solved. My neighbor came by and had a look. It was indeed the darlington. He had a TIP120 handy and didn't think it would cause any issues. I don't entirely trust that assessment so I ordered a few BD679s.

[gr5 2,172]

um1 or um2? If it's a UM1 then, yes, you probably blew Q4. The darlington. If it's a UM2 then this is very unlikely. If UM2, then much more likely is wiring issues near the head -- slide up the black plastic sheathing and check the wiring under there. Note that for both printers the fans don't normally come on until several layers have finished but you can start the fans on the UM2 by clicking PRINT, selecting anything to print, then TUNE and then setting fan speed to 100%. As long as you stay in TUNE menu it will not start printing.

 

[czucker 0]

It's a UM1,by the way.

[gr5 2,172]

 

2 days later he says...

 

It's a UM1,by the way.

 

Ok. Most likely q4. Relatively easy to replace if you have a soldering iron. I would test it first. On ulticontroller set fan speed to 100% and it should come on right away. Measure the voltage at the fan connector on the PCB. It should be 19V. If not, then replace Q4. If it *is* 19V then something wrong with either the fan or wiring.

In this picture below the fan is the bottom edge "middle" connector where it says "pwm" and there is a blue/purple wire. Disconnect that - make sure it's 19V. If it is then nothing wrong with PCB and connect the connector back on and see if that lowers the 19V to 0V or something. Again, this will only be 19V if you set the fans to "255" on ulticontroller.

 

[gr5 2,172]

You can also see Q4 slightly above and to the left of the PWM connector.

 

[czucker 0]

2 days later he says...

 

I'm a very busy man!

But seriously, I'm up in Vancouver for a few days, so I'm not near my printer. I'll be home by the end of the week and should have the proper transistor in hand.

Thanks a million for the very detailed response.

Oh, one more thing. I'm curious about whether or not the TIP120 would be a suitable replacement if I ever have an issue in the future. They're readily available off the shelf.

Thanks,

Chris