Hi im having some issues with my old 1989 sealey mightymig 90, i have removed what i believe to be a thermisto that is across the rectifier and it is testing open circuit/infinite ohms. i have the instructions attached which shows what looks like the thermistor symbol in the circuit diagram but it only has the whole rectifier assembly listed in the parts. what i would like to know is what would be a suitable replacement as searching the numbers on the part doesnt come up with anything [GEU(B or 8 not sure) 68710] im guessing it would be a ntc thermistor to pass current across the rectifier as it heats up? but what resistance value should it have? pictures attached Many thanks
It could be a capacitor to filter hf noise, but I suspect that it's an MOV (metal oxide varisor) or transorb (commercial name for same thing) that is designed to break down and conduct briefly on high voltage spikes a save damage elswhere.
hi dont think its a cap as doesnt look like one and wrong symbol on circuit diagram, could well be a mov though as has same symbol as thermistor on circuit diagram, in which case its testing good and means i have to look else where for whats causing issues, thanks
I agree with awemason, it is an MOV varistor. Quite usual to see them in that location - across the rectifier, for spike protection. The welder will ( should ) work ( or not ) without it. What fault(s) are you experiencing?
Can't see it been a thermistor it wouldn't handle the current, what problem are you having with the welder
