DoAll DBW-15 Blade Welder - short with everything off?
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  1. #1
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    Default DoAll DBW-15 Blade Welder - short with everything off?

    Hi all, after sitting for a couple of months, my DoAll blade welder has developed a problem where, when connected to the wall, it's got a short. The thing I can't figure out is, it's shorting with everything off (no blade in the jaws, no tension on the jaws, flash grinder off, etc). I opened it up and don't see any chafed wires, parts that should be moving that aren't, bad contacts, etc.

    Any advice? I have the manual but it doesn't include a troubleshooting section.

    Thanks!

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    Generally on 220V switches only one wire is broken into the switch and the other is always live, that would explain why it shorts even when not using the switches.

    Check the wiring that does not go into switches to get broken but directly into the grinder... I suspect it might be there. If not start checking the wiring going directly into the welder that do not need to be connected by the contacts when clamped down.

    You never know,it could even be your cable from the plug that has been crimped because it was stood on or rolled over by a trolley. If you have a multimeter check for continuity from the plug side into the unit to see if that is the case.

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    Unfortunately, further digging and connection checking reveals everything is fine except that when power is applied, the main transformer is smoking a bit, even with the jaws open, no blade, and not pressing the annealing button.

    However, as I typed that, I thought to check, and the anneal button has failed closed! I'll disconnect it and see if the transformer is already cooked or not.

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    Nope, that was wrong too. The anneal switch looked shorted in-circuit, but isn't once disconnected. Presumably the short was actually in the transformer and I'm screwed. Crap.

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    I posted that I could rewind the transformer. You possibly can remove the iron core and only send me the windings to save on shipping. There also is a certain possibility that it is the same as the transformer in my DoAll welder, in which case i could copy mine. A picture of the transformer would be a good start.

    I posted this a few days ago but it seems to have gotten lost.

    Bill

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    Quote Originally Posted by JasonPAtkins View Post
    Nope, that was wrong too. The anneal switch looked shorted in-circuit, but isn't once disconnected. Presumably the short was actually in the transformer and I'm screwed. Crap.
    Did you actually check for a voltage potential between the welding jaws when the machine is supposedly off? There must a cutoff switch which gets activated at the inner throw of the jaws. That switch could fail and weld its contacts.

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    Quote Originally Posted by 9100 View Post
    I posted this a few days ago but it seems to have gotten lost.

    Bill
    Seems odd that an offer to help isn't even acknowledged.

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    Quote Originally Posted by Gordon Heaton View Post
    Seems odd that an offer to help isn't even acknowledged.
    Gordon, I don't think it ever got on the thread. This computer is an old Toshiba laptop running Vista, which I hate, that someone gave me. It often does weird things and I thought the entry posted, but apparently not.

    Bill

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    Now you are assuming it is the transformer. I would first prove that by disconnecting ONLY the transformer and see if the short is gone.

    If it really is the transformer, I would inspect it carefully. I would remove it and give it a good cleaning. Start with a brush and shaking it at all orientations to see if anything may drop out. Then use a brush with soft bristles. Finally, use compressed air to blow it out. You can take some resistance readings to see if there is any change from before cleaning to after. Don't forget reading from each of the wires/connection points to the frame of the transformer. If it appears that the cleaning changed something, try it again.

    Also look carefully at the wires going to the transformer. Your short could be there, possibly where one goes around a sharp edge.

    Good luck!

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    Quote Originally Posted by EPAIII View Post
    Now you are assuming it is the transformer. I would first prove that by disconnecting ONLY the transformer and see if the short is gone.

    If it really is the transformer, I would inspect it carefully. I would remove it and give it a good cleaning. Start with a brush and shaking it at all orientations to see if anything may drop out. Then use a brush with soft bristles. Finally, use compressed air to blow it out. You can take some resistance readings to see if there is any change from before cleaning to after. Don't forget reading from each of the wires/connection points to the frame of the transformer. If it appears that the cleaning changed something, try it again.

    Also look carefully at the wires going to the transformer. Your short could be there, possibly where one goes around a sharp edge.

    Good luck!
    I'm reminded of an incident I may have related before about an arc welding machine I once used. I'd used it for a couple of years without any issue. One day, I was doing a bit of welding and touching up the weld with a small angle grinder. I temporarily set the grinder down on top of the welder. Inexplicably, the cable of the angle grinder started to smolder and smoke. I was going "WTF", did a quick double take of all the cables and stuff after unplugging the cord, nothing was out of place.

    So then I opened up the case of the welder, and one of the large wires to/from the main transformer, even though wrapped with insulation tape, was displaced slightly, and was resting against a partition in the welder. I guess typical AC hum had caused that wire to wear through it's insulation and touch the partition. The wire must have been on the secondary of the transformer, I'm reasoning, so the ground fault wasn't apparent until another grounded object (the grinder) made a circuit through its ground wire to the system ground, and back to the welder's chassis and then allowed current to be pulled through the secondary. I'm no electrician, but all I had to do was move that conductor off the partition it was contacting.


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