330 ABP range- polarity selector switch problems

[ratherbhuntin]

I have a 330 abp, I tried to weld with it yesterday, very low output. I noticed when I try to switch polarity there will be sparks coming out just behind the lever. I had a lightning strike a tree about 75 feet away, from my house that still took out one of my TV's, antenna amp, modem and router. I wonder if this can be related. It was working flawlessly before then. I have the manual and parts drawing, looks like there switch plates inside, anyone ever take one of these apart, and do they still make parts? its a '86 model. Thanks.
Charlie

[Aeronca41]

Please post the serial number so we can look at diagrams. I'm not an expert, but without looking at a diagram, my first thought is there should be no way to get sparks from the polarity switch unless something else is wrong. There is generally no current through a polarity switch unless you're welding, and thus nothing to make sparks. Lightning damage is certainly a possibility.

[ratherbhuntin]

Thanks, ser# JH266472 stock #901041 with power factor correction. Hmm, definitely sparks coming from behind the panel where the polarity switch comes out.

[Aeronca41]

What is your level of knowledge of electrical safety and working on powered eqpt? Going to have to take the covers off and see where the sparks are coming from as a start. If you are not knowledgeable and comfortable working on live stuff, just look and take some pix to post, but don't reach in there.

[ratherbhuntin]

I'm fairly knowledgeable, not a expert. But will start by taking the cover off and checking it out. Are parts still available? Thanks for your help.

[Aeronca41]

Probably some parts are avail and some not. Look up the 6-digit part number from your manual and check miller4less.com. If no hits there I'd give a call to Miller to see if the PN may have changed, or if they have it. Also, you can find generic parts locally in many cases if you know what to look for.

Glad to help; hope you can get it working.

[ratherbhuntin]

Took the cover off, definitely sparking on the contacts when going from DCRP to AC, also when I turn the range selector to high it sounds like its under a load. I have a line on another 330 for a hundred bucks, may just get it, its a lot older though, 74 model. Here is a pic, doesn't show much there is some corrosion on the contacts, something is definitely going on.

[Aeronca41]

Will take a look at the diagrams tomorrow and see if I can offer some troubleshooting tips-but hopefully someone who really knows something about this machine will join in.

[Aeronca41]

Sorry to be so slow. Pretty complex machine (at least by old-time standards, but not like one of today's electronic marvels). Hope someone with experience with these machines will join in. In lieu of having someone who actually knows the machine, the first thing I would do is disconnect the remote if you have one, put the standard/remote switch to remote, and see if the switch still arcs. Going to "remote" with no remote connected should remove all power to the polarity switch. Unless the Lightning resulted in some things being connected that shouldn't be, there should be no power to that switch unless you're welding. Contactor W or its control circuits could be the problem.

[ratherbhuntin]

Got into it a little more today, If you turn the machine on and its in AC, then move it to DC rev, the big contactor down by the transformer will engage like its under a load, if you switch the remote switch to remote, the contactor will release, then there are no sparks when you turn the selector or range switches. According to the diagram, I guess that would be contactor W.

[Aeronca41]

Does your machine have the optional spot weld timer described in the manual?

[ratherbhuntin]

It does not have the spot weld timer.

[ratherbhuntin]

Well I'm on the right track, had help from someone who said its probably a bad diode, pulled them out and sure enough, found a shorted one. Don't know if its the only thing but good to find something that is wrong. $67 on miller for less. Thanks, I'll update later.

[Aeronca41]

Great! That's where I was headed next. That would be a good reason for current to be flowing when it shouldn't be. And not a terribly expensive fix.