Sealey welder not working - MIG Welding Forum

I'm new to the forum so apologies if this is in the wrong place.

I borrowed my brother-in-law's Sealey Mighty Mig 100XT welder which is about 20 years old and whilst I was using it yesterday it packed up working. It no longer welds and the wire feed has stopped feeding. I know a bit about electronics so I need to fix this but I can't find a circuit diagram for it anywhere on the net. Does anybody happen to have one they could let me have please?

Also, is there a standard fault which these suffer from? It has power and the fan spins and all the fuses are okay. The wire feed motor is also okay but doesn't run when the button on the handle is pressed although the button on the handle is working correctly.

Thanks, Paul.