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Posted by D Sherman [72.47.9.228] on Tuesday, August 09, 2011 at 17:21:39 :
In Reply to: O.T. old welder problems posted by Dana (in Lancaster) [71.232.236.112] on Tuesday, August 09, 2011 at 17:03:35 :
With electrical problems, there are two approaches: WAG (wild-assed-guesses, aka "shotgun method") and tracing through it (aka "divide and conquer"). Here it's pretty simple. The juice comes out of the wall, goes through the cord, goes through some switch, and into a big transformer. Downstream of that, it goes to your electrodes, with a switch to optionally send it through rectifiers for DC mode. Plus, there's some mechanism to adjust the juice, either by switching taps on the transformer or adjusting its air gap mechanically.
Got juice at the transformer? Then you know it's something downstream of there. No juice at the transformer? It's something upstream. Say you got no juice at the transformer. Pick some point midway between the wall and the transformer, like the first terminals the power hits when it gets inside your box. Got juice there? Then the trouble is between that point and the transformer -- maybe a switch or circuit breaker. No juice? Check the cord and plug. You see how it goes. I can say "maybe it's this" or "on mine it was that", but those are all just WAGs. The thing to do, after looking for obvious broken or burned wires like you did, is get out a volt meter or test light and trace through it. Start in the middle somewhere and then work your way fore and aft depending on which half didn't have juice.
Since the fan and lights work, you know the power is okay as far as the main input terminal block at least. Downstream of there you might have a power switch and/or relay, the transformer itself, a circuit breaker, some kind of thermal overload cutout (possibly automatic, manual, non-resettable), the big honkin' transformer (which should buzz if it has juice to it), followed by the rectifier switch and the welding leads. Go through them step by step and you'll find the problem, which will probably not be anything very subtle.
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