MakerGear Forum

Last night I was troubleshooting my printer's cooling system, and accidentally shorted the fan leads and blew a fuse. I moved the second fuse into the first fuse's slot, but that didn't fix the problem. (at the time, I was thinking that maybe the second fuse wasn't needed)

After replacing the fuse (everyone should buy some to have on hand, MG sells them for $2 each), I found that I can no longer control the 40 mm fans. When the RAMBO board powers up, the fans automatically turn on and neither M108 S# or M106 S# will change their speed. I'm worried because it sounds like they're louder than normal (ie, getting 19 volts instead of 12).

The hotend, bed fan, steppers etc all work. Just the 40 mm fans are being weird. Resetting/ unplugging the printer does nothing.

Do I need to do something with a jumper? I feel like some onboard settings were changed, but I want to hear what you guys think before I start randomly shorting jumper pins together.

It sounds like the Fan1 MOSFET has been damaged from that short - if it doesn't respond to M108, it means that it's not being controlled by the Atmega µC at all. You may need to modify the firmware to use the Heat1 output for the 40mm fans. If you send a picture of your RAMBo, I may be able to determine if there's another option (certain revisions have another Fan output).

Josh wrote:It sounds like the Fan1 MOSFET has been damaged from that short - if it doesn't respond to M108, it means that it's not being controlled by the Atmega µC at all. You may need to modify the firmware to use the Heat1 output for the 40mm fans. If you send a picture of your RAMBo, I may be able to determine if there's another option (certain revisions have another Fan output).

Thanks http://i.imgur.com/dmbvL4e.jpg

Edit: and now, this is what my temperature readings look like... http://i.imgur.com/nylmEPL.png
Double edit: Only when the power is being supplied to the 40 mm fans. M108 S0 makes it go back to normal.

Update:

I still can't control the 40 mm fans, but I have a workaround. The bed fan and the 40 mm fans are now all powered by the Fan2 MOSFET. When I don't need the bed fan to be on, I simply unplug its connector.