Taz 3 stopped connecting USB


My school has a Taz 3 that stopped connecting via USB. It was working last Wednesday night for me and then Thursday afternoon it stopped connecting for the one student who is allowed to use it unsupervised. I checked it today and had the same problems that the student reported. No hardware or software changes had been made.

I’m using a Mac with 10.13.1 and connect using Printrun-Mac-18Nov2017. I also tried connecting with Cura 21.08. The student has a Windows 7 and Windows 10 machine and also tried connecting with Printrun and with Cura.

When connecting with Printrun, it comes up with

and will continue printing out SENT M105 as long as the USB cord is connected to the machine.

The printer still works using the SD card.

I’ve tried changing the USB cord and changing computers. The only hardware issue that we have had lately is an issue with the power supply’s potentiometer needing to be adjusted to increase the voltage. However, I checked that this morning and it was not an issue.


there are two small fuses on the rambo board of the Taz 3, one of them may have failed. They look like grains of rice. It could also be a failed USB port on the rambo board. Or it could be a software configuration change in the computer and its not connecting right, but you’re on your own with Macs.

You shouldn’t have had to adjust the power supply potentiometer. If you did, it may be that your power supply was failing and possibly not outputting the correct voltage at the time you tested it, but later went to full power and melted somethign important.

If its not the fuses and truely nothing changed in the software configuration, my guess would be that you need a new control board. New fuses are $1, a new rambo board from ultimachine.com is $170 https://ultimachine.com/products/rambo-1-3 Or used for $99 https://itworks3d.com/product/rambo-3d-printer-controller-board/ The fuses you need are these ones https://www.seemecnc.com/products/5-amp-cermaic-fuse-for-rambo

If you pull the fuse and it has continuity then it is fine. Be aware that it is possible to pull the fuse contacts out of the board with the fuse if you grip it wrong, ruining the board. And it is really annoying when that happens. Especially if you only have 1 3d printer at the time.

In the event you have to rebuild the control box to put a new board in it, here are the step by step connection instructions: https://ohai.lulzbot.com/project/df9ea50d-8cc7-4993-98b7-231f4dcd355d/taz_3/