Dialarc HF-P blown diode

[Nd2ski]

I picked up a dialarc a while back and hadn't really started using it until recently. I tested it before I bought it and everything seemed to be in order. When I wired it up, I had to change the jumper settings from 230V to 200V to run on 208V. It worked well for a few weeks but last night I was welding some steel and it decide to quit working. I was using a pedal, DC straight polarity, in the middle amperage range with the dial at about 50, remote contactor and remote amperage on, high frequency set to continuous. When I would press the pedal past about halfway, te machine would get noticeably louder. It almost sounded like it was running on AC at full blast. Then there was a "pop" and I couldn't get an arc. Today I went down to troubleshoot it. Checked the fuses in the fuse box and they were good. With it set to HF continuous or start I get a weak arc. I assume it's just the HF trying to start the arc. With the HF set to off, pedal pressed and electrode touching grounded table I get a single spark as I lift the torch but no arc. That eventually led me to check the diodes. There's four of them (2) 037 305 and (2) 037 306. I removed each one and tested continuity. I had one that read 0 in both directions, the other three were fairly similar to each other when measured with respect to their polarity. Before I start ordering parts I had some questions. What causes the diode to go bad? Is it typically just through use or is there an underlying problem that will wipe out the diodes? Do they often fail at about the same time? Should I order a set of them or can I replace just the bad one?

[cruizer]

Replace all of them, and replace the contactor as well

[Nd2ski]

Replace all of them, and replace the contactor as well

The only thing on the parts diagram I can find referred to as contact is part of the mechanical amperage and polarity switches. Are you suggesting I replace those contacts or are you referring to something else?

[MinnesotaDave]

I popped a diode on one of my welders while exceeding the duty cycle (oops, my fault).

I just grabbed one out of an old machine and fired it back up - no problems 3 years later.

However, I did research and order larger ones to replace them all when the next one goes.

Turned out the cheapest source for diodes was from wind generator people online.

[cruizer]

If its a Dialarc HF, it'll have a 3 pole 115 Vac definate purpose contactor.

[Nd2ski]

The page with that on it must not have loaded the first time I pulled it up. According to the manual though it's a 60A 3 pole 600V contactor.

[Nd2ski]

I popped a diode on one of my welders while exceeding the duty cycle (oops, my fault).

I just grabbed one out of an old machine and fired it back up - no problems 3 years later.

However, I did research and order larger ones to replace them all when the next one goes.

Turned out the cheapest source for diodes was from wind generator people online.

Thanks. None of the welding shops around me have them in stock and if I order them locally they want $59 each. Just a quick search yielded windmill generator diodes for less than a third of that price. now that I know they're not specific to this welder I know a supplier that may have them in stock.

[cruizer]

The page with that on it must not have loaded the first time I pulled it up. According to the manual though it's a 60A 3 pole 600V contactor.

6oo v is just a rating, doesn't mean anything, so whAt your after is a 3 pole 60 amp definately purpose contactor. Diodes don't have to be miller specific, however require that pig tail, stud size and polaritys