250EX pedal problem, display stuck at odd values. Plus, unrelated main switch issue.

[Gandalf]

Hello everyone,

I have been happily welding for several years on my 250EX with no issues. In the middle of doing some steel (DC) yesterday, I went to start a new weld and the arc looked very faint... I glanced at the display and it said -24 and stayed there. Yes, that's "minus" 24. I fiddled with the foot pedal a bit, and suddenly it changed to reading 457. Both instances, it is stuck there, with no response as to pedal movement. As soon as I unplug the foot pedal at the machine, the amp display shows normal, where I last left it. 4T works just fine, torch too.

(No pulse. 2T. Freq/bal basically centered)

Argon flow/switch was as per normal on the pedal, arc was starting too.

Fairly clearly I have something wrong in the foot pedal, it is the one that came with my 250EX. It's like the pedal sends the welder into welding mode, just by being plugged in, like it's getting a very low value that doesn't change with pedal movement. Like one wire is shorted somewhere, or in the pot. But it's not the wiring for the switch in the foot pedal it seems... one of the the remaining 3.

A foot pedal is frighteningly simple, basically just a switch and a pot. Can I change out the pot with a replacement? Or don't bother and just buy a replacement pedal? Is it possible to clean the pot? It's not dusty on the pot at all.
I began by eliminating the section of wiring that passes through the wall of the foot pedal casing... the most likely problem area for wiring (since all other connections look normal). Didn't make a difference.

A second but unrelated (I believe) concern - my main switch on the 250EX has begun acting funny, at the top of its throw range. Its as if it shuts off if pushed in the fully onward direction, at the end of it's range. If I apply slight pressure on the switch in a downward direction (towards off, but without actually moving the switch) the unit turns on again. Sometimes it can be indecisive and switch on/off/on/off quickly, as if it can't decide.

Thoughts?

BTW I am otherwise thrilled with the performance and the numerous projects it has allowed me to tackle.

Thanks for reading!
-Martin

[rick9345]

My 250EX on/off acted same way removed switch to get at the bottom screws for the main feed wires, tightened and solved the switch. Stock pedal is funky and off/on micro can hang up along with the belt wheel on pot is prone to slipping and over running pot to ruin.

[Gandalf]

Hey thanks! I will look into those details.

[Grizzly1944]

I know that i might cost more, but the SSC pedals that are sold here are excellent. The 250EX is one real capable machine. My SSC pedal is well worth the money. Especially when you have been using the machine for years now.