Page 1 of 2 1 2 LastLast
Results 1 to 15 of 19

Thread: Reversing polarity on small welder

  1. #1
    Dead or alive... mudtoy67's Avatar
    Join Date
    Nov 2002
    Location
    Tx
    Posts
    4,545

    Reversing polarity on small welder

    I've got an old Astro Power Powermig 130 I want to use as a flux-core welder. When trying to use it the other day, it was welding horribly, so I did a little research and found the welder appears to be wired for DC electrode positive polarity, while the wire I'm using requires DC electrode negative. There are a few flux core wires out there that run DC+, but the ones I have seen are pretty specialized and not usefull for everyday/all position welding.

    I want to just swap the ground (38) and electrode (51) wires around, but the problem I'm running into is the switch to turn on the feed control (30) gets its signal at A1 from the lead going to the electrode (51). This means that if I switch the ground and electrode wires, the current going through the switch and A1 is also going to reverse direction. So I was thinking I need to rewire the welder as seen in the lower diagram. The only problem I can see with this is that the wire going to the A1 terminal of the feed control (30) is now on the opposite side of the transformer (32) as it was before. Do you think this will cause problems?

    If this can't be done the only other options I could come up with is to install a microswitch in the stinger which would then be separate of the electrode power. Or get a new stinger with a switch already built in. Or don't even mess with it.

    BDR

  2. #2
    D-FENS agjohn02's Avatar
    Join Date
    Apr 2004
    Location
    Cowtown
    Posts
    11,900
    is that your modified schematic or one you found somewhere?

  3. #3
    D-FENS agjohn02's Avatar
    Join Date
    Apr 2004
    Location
    Cowtown
    Posts
    11,900
    drink your coffee, then ask yourself this. does a switch care about polarity?

  4. #4
    D-FENS agjohn02's Avatar
    Join Date
    Apr 2004
    Location
    Cowtown
    Posts
    11,900
    in the modified version, A1 is still wired the same and A3 is wired the same but on the opposite side of the transformer

  5. #5
    Dead or alive... mudtoy67's Avatar
    Join Date
    Nov 2002
    Location
    Tx
    Posts
    4,545
    Quote Originally Posted by agjohn02 View Post
    is that your modified schematic or one you found somewhere?
    Quote Originally Posted by agjohn02 View Post
    drink your coffee, then ask yourself this. does a switch care about polarity?
    Quote Originally Posted by agjohn02 View Post
    in the modified version, A1 is still wired the same and A3 is wired the same but on the opposite side of the transformer
    A new thought every three minutes huh?

    The "factory" schematic is the wiring diagram in the manual for this welder. The modified one I did myself.

    I realize a switch does not care about polarity, but the thing I'm having trouble with is the fact the A3 wire will now be on the other side of the transformer. I'm worried that I'll send too much juice through the feed control.

    I might be overthinking things though. IIRC welders are typically operate on constant voltage, right? So if the voltage is the same, and the resistance in the feed control is the same, then the amperage running through the feed control should also stay the same.
    Last edited by mudtoy67; 02-13-2008 at 11:58 AM.
    BDR

  6. #6
    wash, rinse, repeat. sasquatch's Avatar
    Join Date
    Sep 2004
    Location
    Dallas
    Posts
    2,484
    yes. I=v/r

    1976 F-100 Kustom Krawler
    1976 F-150 Custom
    1964 CJ5

  7. #7
    Buckaroo Bonzai!!! Reckless's Avatar
    Join Date
    Dec 2005
    Location
    BFE, Tejas
    Posts
    3,655
    I know on some welders, like hobart, the wires are in the spool housing and its just a matter of switching the wires. But im going to take it that they arent in there.

  8. #8
    Dead or alive... mudtoy67's Avatar
    Join Date
    Nov 2002
    Location
    Tx
    Posts
    4,545
    correct
    BDR

  9. #9
    D-FENS agjohn02's Avatar
    Join Date
    Apr 2004
    Location
    Cowtown
    Posts
    11,900
    Quote Originally Posted by mudtoy67 View Post
    I might be overthinking things though. IIRC welders are typically operate on constant voltage, right? So if the voltage is the same, and the resistance in the feed control is the same, then the amperage running through the feed control should also stay the same.
    Mig is a constant current operation. stick and tig are constant voltage. Thats why you can change the heat (amperage) of a tig or stick weld by changing the arc length (resistance).

    by altering the location of the transformer, you are just changing the voltage potential across the switch. transformers dont create power. i was going the say that same thing you just said about amperage staying the same and it not damaging the switch but i didnt want to be wrong and be at fault for damaging your welder, but i think you are correct. do it and report back.

  10. #10
    Registered User robertf03's Avatar
    Join Date
    Apr 2002
    Location
    Dallas
    Posts
    6,850
    if it uses a FET to trigger the motor, as any fine chinese welder should, switching the polarity will make it not work, as will too high a voltage at the gate.

    leave the switch wired as is, and run an external wire to and from it if you have to
    Last edited by robertf03; 02-13-2008 at 06:31 PM.
    ...

  11. #11
    Dead or alive... mudtoy67's Avatar
    Join Date
    Nov 2002
    Location
    Tx
    Posts
    4,545
    I anticipated the polarity change, that's why I swapped the wires at A1 and A3. But the voltage was a major concern.

    I stopped at radio shack on the way home and picked up a microswitch. I'll wire it up and let yall know if it works.

    If you don't hear from me I've dun been electrocuted.
    BDR

  12. #12
    Rock and Roll AggieTJ2007's Avatar
    Join Date
    Oct 2004
    Location
    Headed back to the Big D
    Posts
    6,182
    can you not dissonect the wire from the back of the feeder and switch with the ground. Probably to easy for this crowd but there had to be somewhere where the lead connects to the gun,
    Quote Originally Posted by afroman006
    Creighton, you have done stuff with that jeep that would make a goat go "holy ****!"
    Quote Originally Posted by afroman006
    So driving by brail is why your jeep looks the way it does eh?

  13. #13
    D-FENS agjohn02's Avatar
    Join Date
    Apr 2004
    Location
    Cowtown
    Posts
    11,900
    whoa, i saw a TLA in there. id go with that as im thinking in simple electronics terms.

  14. #14
    Registered User robertf03's Avatar
    Join Date
    Apr 2002
    Location
    Dallas
    Posts
    6,850
    Quote Originally Posted by agjohn02 View Post
    whoa, i saw a TLA in there. id go with that as im thinking in simple electronics terms.
    tig?
    ...

  15. #15
    D-FENS agjohn02's Avatar
    Join Date
    Apr 2004
    Location
    Cowtown
    Posts
    11,900
    haha, i knew i wasnt actually on your ignore list. you can't quit me.


    Three Letter Acronym

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •