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Thread: Diodes for welder

  1. #1
    Join Date
    Mar 2002
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    Manitoba
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    Post Diodes for welder

    I'd like to add dc capability to my ac welder as others have done / are doing.

    I came across some diodes in the surplus section at Princess Auto today and am hoping that someone can tell me if they're suitable for the job.

    There are two sizes and the store has them labelled only as "large h/d diodes with gate.

    The larger size (only 3 of these) are GE and each has a different No.

    GE 8493623 U505
    ********* U610
    ********* U523

    The smaller ones - several of these:

    GE 8493622 U529
    ********* U434
    (didn't record the second series of numbers on all of the smaller ones bur most seemed to be one or the other of the above)

    Compared to the ones I've seen in the pictures here on the board, these look similar except that they have two small wires along with the heavy cable. Is this to do with the 'gate' and what's the significance?

    Can anyone ID these or point me to a site with information on them?



    [This message has been edited by Herb W (edited 10-15-2003).]

  2. #2
    Join Date
    Dec 2002
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    Post

    With the small wires.. I'd say you got SCR's or Silicon controlled rectifiers..

    Diodes just have a in and out.. usually a stud mount on one end and a terminal on the other for the large ones.

    I got a question, a couple of the dc welders I have junked has had a capacitor, how much does this help? Not all of them, just some of the welders. I remember a old craftsman welder that tig'ed really good, it had one.

    I have one more set of diodes, but money is in transit for them. The good thing about getting these outa these welders was that they had the heat sink already on them.


    David..

  3. #3
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    Post

    Those are General Electric thyristors. They are what is also known as a "solid state relay" used for full phase control of ac loads. The GE 8493623 is rated at 250 amps, 1200 volts.

    I couldn't find the spec for the smaller unit but is surely less. Trying to find stuff at GE's web site is hopeless.

    Not suitable for DC rectification of a welder.
    Free software for calculating bolt circles and similar: Origin now settable to bottom left! All values positive. Click Here

  4. #4
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    Herb..

    GAEwen posted a week or so back.. they had some cheap diodes listed with a supplier. I think about 30 a piece.. you need 4 to make a bridge.

    David..
    retrieved it for you..


    posted 10-09-2003 11:15 AM Click Here to See the Profile for Evan Click Here to Email Evan Edit/Delete Message Reply w/Quote If you can avoid do not send stuff to Canada via a courier service. It will have to be cleared by a customs broker with attendant expensive charges. The best is to send parcel post via US Postal Service.

    As for the diodes see here for $31.38US

    http://www.galco.com/scripts/cgiip.e...earch-name=NBR



    [This message has been edited by ibewgypsie (edited 10-16-2003).]

  5. #5
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    Ibe,

    I put a capacitor in my DC converter. Under no load it charges up to the full wave voltage provide much higher voltage for striking the arc and a momentary extra current surge to initiate it. Unless the sucker is honking huge it isn't going to make much difference when actually welding. Makes the welder more dangerous, DC kills much better, especially filtered DC.
    Free software for calculating bolt circles and similar: Origin now settable to bottom left! All values positive. Click Here

  6. #6
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    Thanks guys!

    I'll go back and read that thread.

    edit:
    That was fast...thanks again David

    [This message has been edited by Herb W (edited 10-16-2003).]

  7. #7
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    Herb..

    Actually, before I'd put another hundred into the welder you have... I'd look for a square wave machine. We bought several at auction recently for less then 50 each.

    I do not have any for sale at the moment. Sorry friend.. But I will keep my eyes open for more.. MUCH smoother burning rods.. Smooth sounds, steady beads..

    We bought two plasma cutters for 60 each. After I had bought the 3 phase one for 250..

    If you give me a week, I can probably find you some diodes much cheaper then the ad I posted before.. I was selling them to "US" HSM'ers for 35 plus postage.. what we had in the HUGE 3 phase welders each. I sold the welders then bought the diodes back. If I had of had the time to remove them myself, I could have shipped them for postage only.

    Evan is pretty sharp on these things, and I am up to my hips in work at the moment.

  8. #8
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    Very kind of you David...no hurry though, I won't have time to work on this for a while anyway.

  9. #9

    Post

    Hey, I'm new to the board.
    I have some experience with electricity and welders. It just so happend that when I was rummaging around today I found several diodes that would work for adding dc capebility to your welder. Contact me off list and I will see if i can send you some.
    contact me at cinexero@yahoo.com
    -xero

  10. #10
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    Hi Xero, welcome to the board!

    You have mail...and thank you very much!


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