My fine adjust reahstat is burned below 70%

Welder still runs well above 70%
Machine is a 1984ish big 40

Burning 1/8 7018 at 130 and 160 volts it got pretty toast to the touch on panel behind coarse and fine adjust. Could hold my hand on it but its pretty darn warm. Uncomfortably warm

Machine runs smooth on both coarse settings set at 70% fine setting.

Should I be concerned. Normally I dont turn fine up to over 65% and run it around 30-40% doing vertical runs.

I'm very limited at 70% but thought I'd run it limited until it burns out the rest of way or just stops welding.

I sure dont want to burn my pickup down

Thanks for any advice.