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Calling Brasco

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  • Calling Brasco

    Brasco,

    While using my ancient P&H welder this weekend it appears that I let the smoke (or selenium?!) out of the main selenium rectifier

    In a discussion with Visegrip he suggested that I contact you about the process of changing out the selenium stack for a diode style bridge rectifier.

    Any hints, tips or suggestions for me on how to go about this?!

    Thanks,

    Brad
    Last edited by bkahler; 03-27-2007, 05:00 PM.
    ________________________
    Richmond, KY

    Hobart BetaMig 200
    Linde HDA-200 AC/DC Tig/Stick
    Dayton Buzzbox

  • #2
    Hi Brad I'll look over the prints, I should have some diodes for you also.
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    • #3
      Originally posted by Brasco View Post
      Hi Brad I'll look over the prints, I should have some diodes for you also.
      That would be great! Used the P&H a lot of hours Friday and Saturday and was extremely pleased with the quality of the welds. Unfortunately my abilities are not currently up to par with what the machine can deliver

      Thanks!

      Brad
      ________________________
      Richmond, KY

      Hobart BetaMig 200
      Linde HDA-200 AC/DC Tig/Stick
      Dayton Buzzbox

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      • #4
        Hi Brad, when you buy a set of diodes make sure you get a rating above the welders capacity, that means for a 200 amp welder go to 300 amp diodes etc.
        They may cost a bit more but when you work with electronic stuff at their rating value you'll find that the rating is for the absolute maximum power handling and even with the best heatsink will not last the day.
        So you just halve the rating and they'll last a lifetime.
        The main rating is the amperage with the voltage greater than the maximum welder output voltage.
        The other thing is to get both types of diode, 2 with anode stud and 2 with cathode stud, so that the heatsink is a simple alluminium plate.
        The heatsink should be mounted vertically not flat, as the metallic dust and dirt will build up on a flat plate and could lead to shorting out the diodes, especially in a welding shop where a lot of metal dust is hanging in the air.
        And last but not least if you don't have a cooling fan in the welder fit one and make sure the heatsink gets a bit of fresh air as well.
        I bought a set of five 1n4045, 275 amp 100 volt diodes, (one spare), for $US69.00 from Pembleton Electronics, 1410 Griffin Street, Fort Wayne, In 46803 october last year, on Ebay, and had them shipped to OZ for US$18.00.
        Came in 14 days.
        The diodes are used in a bridge rectifier configuration and will replace the selenium rectifier without any other changes.
        Just make sure the heatsink is isolated from the casing with insulators, and has plenty of ventilation as they can run hot under load.
        Hope this helps.
        Ian.

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        • #5
          Originally posted by billbong View Post
          Hi Brad, when you buy a set of diodes make sure you get a rating above the welders capacity, that means for a 200 amp welder go to 300 amp diodes etc.
          .................................................. .............Just make sure the heatsink is isolated from the casing with insulators, and has plenty of ventilation as they can run hot under load.
          Hope this helps.
          Ian.
          This is great instruction ....thanks ..........I'll put up pics of the six ones He can have.... for evaluation!!

          Phil

          No time to hoste them !!!!!!!!!
          Last edited by vicegrip; 03-28-2007, 02:40 PM.
          sigpicViceGrip
          Negative people have a problem for every solution

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          • #6
            Ian, thanks for the info. Good point about mounting the diodes on a vertical surface. In the P&H configuration that would also provide the best angle for the flow of air to the diodes.

            Phil, I think I managed to get the numbers of the diodes in your pictures. I'll do some research today and see if I can find out their ratings.

            Thanks!

            Brad
            ________________________
            Richmond, KY

            Hobart BetaMig 200
            Linde HDA-200 AC/DC Tig/Stick
            Dayton Buzzbox

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            • #7
              this post is a little old but here goes. i have a P&H TL-180. i'm not much of a welder. i up graded the capacitor with a new one with twice the uF of the original i believe than perked the welder up. now i'm thinking of replacing the selenium rectifier with a full wave bridge rectifier. i just don't quite know which wires go where. i can see the one power wire from the switch. one comes?? goes to the amp select dial. the other two wire come ?? go to the welder coils. any input about wiring would be appreciated thanks

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              • #8
                i can't find any dc voltage but my ac output is 57 volts high amps.67 volts low amps. i'm thinking the selenium rectifier is leaking back ac.

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