Old Weldmate 225 schematic sought

[drummadude]

I picked up this ancient stick welder and found someone had replaced the power cord, the end has some melting around one of the hot plug tines. The power control knob where the cord is wired needs to be checked, but I cannot find any resources. Would anyone be able to assist me? Thanks in advance.

 

[voipio]

Welcome to the forum.

Info on this welder seems rather elusive, as you've probably found already.

In the absence of a schematic, or user manual, a few good pics of the internals might allow forum folk to provide some useful suggestions.

 

[drummadude]

Thank you for the reply, I am attaching pictures as suggested.

 

[voipio]

Is the melting mentioned in the original post, clearly visible in in the images? If so, I cannot see any melting, as such. Melted copper would normally also melt the insulation around it, and possibly cause charring. One of the wires to the transformer, or thermal cutout, looks like it might have had solder flowed into the end, to give a better contact, possibly. Might that be it?

The connections to the power switch look OK. With the welder power switch off, use a multimeter to check that the mains wires coming into the switch go to the correct pins on the plug, and that the ground connection is also correct.

One way to test the welder would be to put a 220V tungsten filament lamp rated at around 100Watts, or heater load (or two 110V filament lamps in series) in series with one of the wires on the incoming supply, to limit the current, and turning the welder on. If the lamps light briefly from the initial current surge and then go dim, and the mains neon on the welder lights up OK, then it should be good to go. If the lamp(s) stay brightly lit, once the power switch is turned on, or are brightly lit from the start, further investigation will be necessary.

 

[drummadude]

Voipio ,thank you for the reply. I was in the process of replacing the cord end where the melting was observed, hence I did not include a picture of that piece as I cut away the end. There is a ground screw on the back of the knob control where the wiring is landing and a grounding termination on the front panel where the power cord is landed. Should there be a jumper between those two points? Another thing I noticed, after posting originally and finishing up re-terminating the cord end is this cord they used to replace the original is rated at 30A and on the cabinet silkscreen it shows a 50A rating. I will be back to my shop tomorrow to continue working on it and will gather more information.

 

[voipio]

A ground wire to the switch ground terminal would improve safety, specifically by grounding the knob spindle to prevent it from becoming live under certain switch fault conditions.

A 30A rated cable should be sufficient for a 225A stick welder. The 50A on the rating plate might be the surge current. What is the value of I1eff shown on the rating plate? I1eff is the value used to determine the required breaker and supply cable and also the power plug/socket + mains cable.