Hi all, I recently purchased a used 250EX (analog controls) and am scratching my head on why it'll HF start cleanly then hold what seems like a normal DC arc regardless of DC or AC mode.

I've confirmed with tech support that I've got things plugged in correctly (torch -, clamp +), but in AC mode I get the same quiet, stable (I think, this is the only machine I've used) arc that responds as expected to pedal inputs and amperage control but doesn't seem to change at all with any combination of frequency or balance settings. Results are a brown mess with no visible cleaning on 5000 and 6000-series aluminum but seems OK on mild steel.

The gentleman I spoke with suggested inspecting the AC side of the machine for any smoked wires or IGBTs, and indeed there is a cooked purple wire that seems to run from the negative bus bar through another board to what I think is a big soldered board attached to IGBTs?
Click image for larger version.  Name: PXL_20220316_133115595.jpg  Views: 227  Size: 143.5 KB  ID: 14133 Click image for larger version.  Name: PXL_20220316_133144588.jpg  Views: 227  Size: 148.8 KB  ID: 14134 Click image for larger version.  Name: PXL_20220316_133157392.jpg  Views: 219  Size: 145.0 KB  ID: 14135

Photos are both from the back right side of the machine as pictured:
Click image for larger version.  Name: PXL_20220316_133214669.jpg  Views: 224  Size: 151.2 KB  ID: 14136

Should also mention that I initially miswired a NEMA 14-50 plug onto the machine (yes, I know, Everlast has restored my faith in manuals) and had neutral connected to one phase. Looking at this purple wire I'm fairly certain it smoked a long time before I touched the machine, but perhaps I've got two unrelated issues here.

Any idea what this wire is (was) doing? Would love to probe further but I'm not entirely sure what components to cast suspicion on. Thanks for any guidance!