Hello, I have been working on a cp300 that I bought to use in my shop, When I got the welder, the control relay cr1 was bad and it would'nt do anything but run the fan. I replaced cr1 and the welder would weld, but after a short period (1/3 of a 1/8" 7018 ) it will just lose the arc. in a moment it will weld again, well arc again anyway, but it is an erratic arc, acting cold one second and hot the next. When I got the welder the jumper links were set to 480v I set them to 230 and have rechecked their position to make sure they were set correctly. The power in the shop measures 240 leg to leg, 120 to ground on two phases and 235 or so to ground on one phase. I have the wild leg connected to L2. I tried jumping the thermostat to make sure it was not opening, and it made no difference. I checked the contacts and while they didn't look new they didn't look bad. I have cleaned the cable connections. I put a meter from the positive to work legs and the voltage is erratic. The surface of the coils where the brushes meet them look ok and are not pitted. If anyone has been there done this I would appreiacte any help youi could offer. I would like to fix this old welder and also use it with a s-22a feeder. thanks -dave
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Miller CP 300 Problem