Wire feed running flat out?

[chevy2]

A friend of mine has this murex mig but recently it only feeds the wire at full speed?,
any ideas of any common faults as he'd like to maybe repair himself, ta.
Yeah I know the wire speed knob is missing in the pic as I think he's started to investigate the problem.

 

[shenion]

Usually it would be the transistor on the control board shorting out.

 

[chevy2]

Usually it would be the transistor on the control board shorting out.

Thanks, I'll pass the info on.

 

[Welderfix UK]

Yeh, could be a TRIAC though rather then a transistor. If you follow the wires from the wore feed motor back to the control board you should be able to identifiy the device.

 

[chevy2]

Yeh, could be a TRIAC though rather then a transistor. If you follow the wires from the wore feed motor back to the control board you should be able to identifiy the device.

Thanks i'll mention that also.

 

[Welderfix UK]

Of course in your picture it's not just the knob missing - it looks like the entire potentiometer so this is obviously the first thing to sort.