Hotend shows 0ºC after overheating several times (UMO+)

[veedee 4]

Hi All,

One of my older type UMOs with heated bed upgrade has shown some temperature issues. When it was printing, the room started to smell like very hot PLA, you know, that semi sweet caramel-ish odour. Well, things turned out to be the hotend overheating while printing. It started of printing normally, but after a few minutes, the filament got so hot that it ruined the print. So I tried this a few more times and the same thing happened. I shut down the printer and got to bed. The next day I wanted to test if the printer also went overheated when I only heat up the hotend, but to my surprise the hotend now shows 0ºC.

So I expect the sensor to be broken, because I don't get any MINTEMP or MAXTEMP errors. Can somebody confirm this? Or do I have to look at the amplifier board?

Also, my newer UMOs only use a PT100b sensor without that board, resulting in a cleaner wiring. Is there any way to convert the old amplifier & type K thermocouple setup to a PT100b? If yes, is there a step by step guide somewhere?