So I figured this would be the best place to ask for help on my early 90's Miller Dialarc HF-300. I bought this machine used about 4 years ago and have had great success with it. The previous owner had built a rolling cart with a 30 gallon stainless steel tank for the watercooled torch. Its a great welder and I've been very happy with it for the time I've used it which is about 5 times a month. I've gone through 5 bottles of argon since I started using it 4 years ago. All that being said, today while welding some .250" thick aluminum plate I experienced what can only be described as a surging or cutting out of the arc. I could hear the HF buzzing along as I have the HF on Continuous for welding in AC, but the arc was intermittent and pulsing on and off. This has never happened before and I stopped to make sure I had a good positive ground but everything was fine.

Has anyone else ever experienced this? Could this be a failing transformer inside? I have the amperage settings on the middle position with the dial at about 90%. So its not running at maximum or anything. I'm just a bit miffed as I've been very good to take care of this machine.

On an unrelated note I've noticed what sounds like a failing bearing on the cooling fan but the fan continues to work fine and has never stopped, just whines a bit. So at some point the bearing will need replacing.

Thanks for your help. Talk soon Travis