Melzi Board Failures

Has anyone else had any problems with Melzi boards failing?

I just replaced my second board in around a year. Both times the failures resulted in inaccurate temperature readings and hot end temperatures extremely high, 300c +. Seems that both times, there was some sort of feedback into the computer usb port that completely shut it down. An instant shutdown, like someone pulling the power. After restarting the computer and printer, the temperatures on the printer were bizarre and running high but everything works fine, its just the temperature related circuits that are jacked up. This last time, I did confirm that there were no shorts, no loose wires, and the thermisters and resistors operating within spec. Just replaced the board, and everything started running perfectly again. Time to order some spare boards just in case!

I'm stumped on this one at the moment. Hopefully no one else has this problem though.

Thanks,
John

Almost certainly an intermittent short circuit between the heater and the thermistor. That would give the symptoms you describe and I can't think of any other fault that would give them.

---

[www.hydraraptor.blogspot.com]