No kidding! When I first started learning to use my Lincoln Square-Wave TIG 300, I was actually WELDING with HF only. I never got the electrodes close enough for the main welding current to flow! That was awesome that it could melt thin metal just with the HF! Under the right conditions, I can get 1", sometimes even 1.5" arcs from the HF, it looks just like those plasma globe things. (After an hour of fooling around, I discovered the main welding current by squeezing the finger control more, getting the electrode closer, and getting a real arc to develop.) But, clearly, there is NOTHING wrong with my HF generator.
I know that the HF system is the reason many TIG welders get junked or converted to stick-only. The main transformer is generally very robust, but the caps, HV transformer and spark gaps all need to be maintained.
Jon