Wia 180 mig.

[Relic]

Have another headache in pipe line.
Elderly WIA mig has come in.
Melting wire at rollers.
Have continuity to earth off secondary winding of transformer.
Have not delved into yet.
Suspect earthed screen between primary and secondary windings.
Maybe failure of screen to secondary winding.
Could have shorted devices for supression at terminals.
Have to check wire feeder isolated to frame.
Any thoughts on this?

 

[eddie49]

"WIA" : Welding Industries of Australia. A home-grown machine - but used to be sold by Cromwell in the UK:

Wia CP119-0 WELDMATIC 10MM MIG WELDER CP119-0 | Cromwell Tools

WIA Weldmatics - choosing the right MIG welder for the job is important. Welcome to the WIA (Welding Industries of Australia) Weldmatics. A range of powerful models (single and thr CP119-0 | Cromwell Tools

www.cromwell.co.uk

I suppose that one end of the transformer secondary, or one side of the rectified DC output, has somehow been shorted to the frame. If the welder is set up for solid wire with gas, that would be the negative side. Measuring the RMS DC voltage, or viewing it on a scope would confirm if it is the AC or the DC part.
I guess the wirefeed-assembly-to-frame isolation must be OK, otherwise the welder would short and trip the input breaker as soon as the trigger is pressed, even without loading any MIG wire.
The rollers, gearbox, motor, and torch socket are all "live" ( i.e. positive ) by design, so if the MIG wire is melting at the rollers, the "other" end of the wire has to be negative somehow?? Maybe the wire is on one of those metal basket spools, and shorting to the frame?

 

[Relic]

Sorry about delay posting.
Dug into this unit today.
Found front plate with sockets etc on wire feeder was touching insulated front bolt on wire feed motor.
Shortened bolt and fitted a split length of hose to prevent future problems if front plate got bent.
Good insulation values to frame after this at wire feeder.
Perished rubber flex for mains power to be replaced before futher digging.
Secondary to frame in kohms with multimeter.
Manuals library has info.
Should be isolated.
Fitted plastic caps over feeder motor mounting bolts as underneath feeder.
Easy to short to frame if placement care not taken.
Super large diodes.
Not going to easy to get at inside owing to construction.

 

[Relic]

Connected 2 of 12volt lamps in series with a clip on lead at center connection.
Clip to frame .
Jumper wire across gun switch socket to close contactor.
Touched series lamps across output at 20volts DC.very quickly.
Both lamps lit with equal brightness.
If there was a serious problem on either leg, one lamp wouldn't go.
Other would have burned excessively bright..
Looks like a leakage issue rather than hard to earth.

 

[Relic]

Welds without melting wire at rollers.
Welds very well at low current settings.
Owner happy.