Help please! My machine is behaving most rudely. It starts off fine an after a few seconds the main arc goes out and just leaves the HF arc and a hissing sound. When I start the machine cold it works for a few minutes before doing this. After it warms up I can only weld in 1 second bursts. It does the same thing in AC or DC. If you have an idea what this might be please post it or email me at email@example.com.