I picked up this Miller 3 phase 400 amp DC welder.
The fella I got it from told me that one of his employees said that it simply quit. Nuther fella he took it to for repair quoted him $950, had a bad circuit board. On the scrap pile it went.
I got it for a song and when he asked me what I was going to do with it, I told him that I was going to fix the circuit board.
I took it home and found that it had no cirruit board in it. It was built in 1958, long before circuit boards were even invented.
I have checked all the rectifiers in it - seleniums. They all have good front to back ratios. The control rectifier bridge also seems to be good. The choke has continuity, the power switch is good and the circuit breaker (heat ativated) is good also.
I can't believe that the transfromers are bad but since I don't have 3 phase here, I can't hook it up and run it. I do have a 5 HP rotary but am not willing to hook it up to the welder.
What would happen if I hook up a single winding to 220 just to test it at low current ?
Oh, and does anybody have any ideas on what might be wrong with this thing ?
JW