I need some help with my Syncrowave 250. Its a 2000 model with low hours on it.

Earlier this week it was working fine. Tonight I went out to weld some aluminum, set the output to AC and the HF to continuous, stepped on the pedal and got nothing.

Switched over to DC and HF start, but HF start didn't work. It will hold an arc when scratch started.

Dressed the tungsten HF electrodes and reset the gap at 0.008in. Now I can get momentary HF but it won't stay on.

Exercised the HF strength knob a few times but didn't help so I pulled the covers and blew the machine out with compressed air.

If I wait 30 seconds the HF circuit will run for about 5 seconds and then dwindle out. Let the pedal up and wait 30 seconds and get 5 more seconds of HF.

Nothing inside the machine "looks" wrong, there was only minor dust build up in the machine, hardly enough to blow out.

Thoughts or suggestions on how to get the HF working again?