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Help My poor ol 330A/BP

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  • #16
    Ok back to it for now I can weld with AC stick (well as good as I expected) I was surprised how easy it was to strike an arc. I did it with multiple currents and all was as I would expect. I also tried DC .. acted just like the tig. What does this mean? I suspect diode in a rectifier. Thats just my poor guess. OK Aeronca41whats next. I'm going to read some more post...

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    • #17
      Nice, easy to start arc, even with AC, is what these machines are all about.

      Yep--I'd be checking diodes next. I have never had hands-on inside one of those machines, so I'm not sure what the diodes look like or where they are, don't know if they're pucks or studs or what, but Ryan Jones is watching this thread and he has a good deal of work time in the circuits of Helga the Heliwelder--we got his playing a couple of years ago and she's been faithful to him ever since; he can probably help if you can't find 'em.

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      • #18
        I'm headed out to the fire station this morning, but if you haven't found them by tomorrow when I get home, I can pop the side off Helga and post a picture. They're easy enough to find and if my memory serves me correctly, they're on the right side, up towards the top above the rack of relays.

        I had a conversation with a man named Jeff at Miller a couple years ago about these diodes. He is, by all accounts, an old machine expert and is likely one of the few still there that has actually worked on one of these old girls. He actually recommended replacing them in my machine, even though they tested fine. I generally don't mess with things if they're still working fine, so I haven't done it. They don't make that part anymore, of course, so you'll have to make an updated something-or-other to fit. Should be easy enough, there's a good amount of space in there.

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        • #19
          Click image for larger version

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          Thomas G,

          If you find that the diodes are bad, I have some left from a repair to my old Airco Heliwelder.

          The part number is SK 6554. Specs are 300 amp - 400 volt.
          DO-9 (Diode Outline) Threads are 3/4-20.

          Here is part of the 330 A/BP schematic showing the diodes.

          Miller Dynasty 350, Dynasty 210 DX, Hypertherm 1000, Thermal Arc GTSW400, Airco Heliwelder II, oxy-fuel setup, metal cutting bandsaw, air compressor, drill press, large first aid kit, etc.

          Call me the "Clouseau" of welding !

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          • #20
            ...and there you have it. Isn't this just a fantastic source of people helping people!

            Thomas, if you end up changing (a) diode(s), I would probably change all of them so they are matched together in the bridge. Probably not absolutely essential, but I would. Also, there are five capacitors in that assembly that I would also replace--they are really cheap, and they are there to protect the diodes. If you do have a failed diode, it does not necessarily mean it's little protective capacitor failed, but it could have, and allowed a transient pulse to hit the diode. The caps bypass transients around the diode to protect it. The little ceramic .01's are pretty bulletproof, and are likely just fine, but I'd change 'em anyway after all these years. If not, I'd at least replace the one called out as paper/oil with a modern polypropelene cap. The old paper/oil ones do go bad. You can order caps from a reputable distributor like Mouser, Digi-Key, Allied, etc. Don't get them from a surplus site like Skycraft or Marlin P. Jones--I buy stuff from them all the time for experimenting and small electronics repairs, and have not had a problem, but I would always get "first line" parts for "industrial" applications like a welder.
            Last edited by Aeronca41; 03-21-2019, 01:44 PM. Reason: corrected type of capacitor

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            • #21
              This is really cool! I am actually having fun at this You guys a great the help. I REALLY do appreciate it.
              I was looking at the rectifiers on the side SR2 and 4. They must have been replaced before as they do not look like the drawing and are glued(?) in place. The SR1 (to me) seems to be a likely if i read the schematic right. Do I need to disconnect the diodes to check them? At least one side. I am more that willing to do what it takes to get this thing working. I tend to be more mechanical than electrical
              Thanks burnthands do you have 4 diodes? are they new? Thanks for the tips Aeronca41. Thanks to you too RyanJones. Is that an El Camino I see in your avitar? 1970ish. I have a 59.

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              • #22
                You heathen...that, my poor, blind and ill informed friend, is a Ranchero. How dare you put a bowtie on such a fine specimen of manly metal. First Helga is insulted and now the Bamchero?! Screw you guys, I'm going over to the lincoln welding forum....

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                • #23
                  Originally posted by ryanjones2150 View Post
                  You heathen...that, my poor, blind and ill informed friend, is a Ranchero. How dare you put a bowtie on such a fine specimen of manly metal. First Helga is insulted and now the Bamchero?! Screw you guys, I'm going over to the lincoln welding forum....
                  Oh, wait---Lincoln doesn't have a forum....don't worry, Thomas--he'll get over it. And Helga already has my sincerest apologies.

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                  • #24

                    Yep--SR1 it is. You need to disconnect one side of each diode to test them. If your meter has a diode test function, your estimate of about .5 v drop forward should be good, and open (OL, infinite resistance) backwards. We're kind of jumping to the conclusion that you have a bad diode, but I think there's a really good chance you are going to find a bad one. Some welders use "positive" and "negative" diodes (straight and reverse polarity); that is, the mounting stud will be the the cathode on two of them and the anode on the other two. From Burnt Hand's partslist, you can see yours uses four the same; the only reason some machines have different polarities on the diodes is to make mounting them to common heat sinks easier; the 330A/BP was top of the line and that short cut was not taken. When you check them, you should get current flow through the diode (continuity) with the negative meter lead on the cathode (the straight line) and positive lead on the anode (the triangle). Out of an abundance of caution, I would also buy some thermally conductive silicone heat sink compound and smear it on the mounting surfaces when you bolt them in. (It is not the same stuff as the silicon grease you use on distributor caps, plug wires, etc., have to get it from an electronics place).

                    You mentioned earlier that it appears some diodes had been replaced and had been "glued on"; would be interested if one of those is the failed part. These things carry the full weld current, and I would question the ability of any glue, even thermally conductive epoxy, to transfer enough heat to keep them alive in the long run. I obviously could be wrong, but I'd really be surprised if that worked. Big bolts are good for transferring heat!

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                    • #25
                      Oops--I misread your post about the glued-in-place diodes. The smaller ones are not as heat critical, and are sometimes glued in place.

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                      • #26
                        Originally posted by ryanjones2150 View Post
                        You heathen...that, my poor, blind and ill informed friend, is a Ranchero. How dare you put a bowtie on such a fine specimen of manly metal. First Helga is insulted and now the Bamchero?! Screw you guys, I'm going over to the lincoln welding forum....
                        you mean an El Camino looking Ford Must be one of those mid seventies models. Look like they stoll the roof design from the Elky.

                        My Dad had a 70 GT and still has 70 gt torino rag top.

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                        • #27
                          Well, checked the diodes. 2 are .49 V drop one way open the other, 2 are shorted - 0.0 ohm ..... if I did it right. Look like I need to get more parts.

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                          • #28
                            Originally posted by Aeronca41 View Post
                            Oops--I misread your post about the glued-in-place diodes. The smaller ones are not as heat critical, and are sometimes glued in place.
                            looked closer and it not glue, it is dialectic heat sink grease

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                            • #29
                              So I have question... what would make the difference from a what is in the 330A/BP - 275 amp 300 v diode and say a 300 amp 400 v diode or even 300 A 1000V?

                              and can the ranges be miss matched?
                              Last edited by Thomas G; 03-21-2019, 03:39 PM.

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                              • #30
                                Click image for larger version

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                                Thomas,

                                It is safe to replace a diode with one with ratings above your original ones.
                                According to the schematic I looked at, D1-D4 are either rated 150 amps at 300 volts or 275 amps at 250 volts.
                                The ones I have are rated 300 amps at 400 volts which provide a good margin of safety.

                                I have 4 and they are new or they were new when I bought them many years ago.
                                Just sitting on a shelf gathering dust.
                                They are straight polarity just like yours.

                                The stud size is 3/4-16 not 3/4-20 as I mentioned earlier.

                                https://www.vishay.com/docs/93508/vs-300urseries.pdf
                                Miller Dynasty 350, Dynasty 210 DX, Hypertherm 1000, Thermal Arc GTSW400, Airco Heliwelder II, oxy-fuel setup, metal cutting bandsaw, air compressor, drill press, large first aid kit, etc.

                                Call me the "Clouseau" of welding !

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