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Thread: 250 Pi small footpedal mod, big return

  1. #1

    250 Pi small footpedal mod, big return

    So I recently bought this welder used. Longevity Weldall 250 Pi. Shortly after I bought it, the foot pedal quit working, so I took it apart, and found the rheostat was failed, no big problem. That is until I tried to find a new rheostat. I found one that was close, but while I waited, I was able to build a new wiper arm, and make it work. I have the new one now, but its working, so I will put it in later, it may add some more fiddling. Sorry I did not snap a pic at that time, but perhaps when I put in the new rheostat I will take it back apart and upload a pic.

    So all is fine and well, but it frustrated me that I could not get an amp readout for max amps on the pedal while sitting static. With the pedal plugged in, it is just a garbage reading until you are welding. It is a little hard to see the readout when the lens darkens haha. I was also unhappy with the range of the pedal, so back in I went. I took the cog belt off, so I could get a feel for how it all worked, and started playing with the two rheostats, when I noticed that I could get the display to read what looked correct with both rheostats at full on, and no microswitch (switch open) the display showed 256 amps. So some more playing, and that was certainly the case, I verified it by setting with the switch open, and then close the switch and going full pedal, while watching the display. (that was tricky)

    So experimenting was over, time to put things to use. I adjusted the pedal actuated rheostat so that I got full sweep from it when depressing the pedal. Then I saw there was an extra hole in the front board where the adjustment rheostat is. It was an exact fit for a toggle switch. I put a SPST toggle switch in the hole, and soldered one side of the microswitch in series, this when open will not start the arc, but with the pedal all the way on, you can adjust the rheostat so that it now adjusts the display to what max amps will be at full pedal. I am also quite happy that the pedal now has much smoother range as well, due to the adjustments I made.

    So now with the new switch open and full on the pedal I can set the amps on the display, release the pedal, close the switch, start welding, and have the correct limit of amps as set, and I have great feel in the pedal.

    Now for a pic, note the blue wires.

    Name:  IMG_0470.jpg
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    Now the next project, I want to make the pulse work with the pedal!

    Many thanks to all the posts I have read here trying to figure out the pedal.

  2. #2
    Hi and welcome to the forum. Nice job on the pedal, I'm sure others will find this useful.
    dan
    Units owned Longevity PROmts 200

    Force Cut LP80 plasma cutter
    Longevity auto dark welding helmet

    Atlas 10x36" lathe
    Craftsman 5HP 30 Gal compressor
    Home made CNC router/plasma/hot wire foam cutting, 3D printing table powered by Longevity Force Cut LP80
    Home built aluminum foundry, HF 4x6 bandsaw

  3. #3
    Senior Member Sling's Avatar
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    Jan 2015
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    Wash DC metro
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    You may have voided your warranty!

    Kidding. I love a good hack like that. Nice job!
    Victor o/a
    accumulating tools as projects demand

  4. #4
    Senior Member JustinWC's Avatar
    Join Date
    Mar 2014
    Location
    Fort Washington Maryland
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    424
    Dang, that is a sweet mod. I wonder if I could do that with my Thermalarc pedal?
    Best regards,

    Justin

    Thermal Arc 186 TIG/Stick
    Lincoln SP-180T with spool gun
    Lincoln Electric Powermig 256
    Longevity Forcecut 42i
    Scotchman 275LT Cold saw
    Milwaukee Portaband
    HF 4x6 bandsaw

    JET HVBS-710SG 7x10-1/2 inch Geared Head Mitering Horizontal Vertical Bandsaw
    Evolution Rage 3 Dry saw
    (OLD) Rockwell Delta 16 Speed drill press
    29 Gal. air compressor with water trap and desiccant dryer

  5. #5
    Senior Member
    Join Date
    Dec 2010
    Location
    Andover, Ohio
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    Welcome to the forum.

  6. #6
    I may have to try this on my pedal. I think my rheostat needs to changed out because I have almost no adjustment with it. I just use it turned up all the way.
    Steve
    Miller Dialarc 250
    Lincoln Ranger250
    Longevity TigWeld 200DX

  7. #7
    I am so going to do this to my pedal. I went out this evening and just to try it out I taped the micro switch down on my pedal instead of putting in a switch and it worked perfectly. I could see just how many amps my machine was set at without firing it up (energizing the HF). I thank you Alta Racer. Wish I had known this a long time ago. I have always thought my fine control did not work but I could tell that it just is very touchy. A very and I mean very small adjustment of the knob makes a big swing in amps. From about 185 to about 150 is just almost a touch of the knob not what you would call turning it by any means. To the store tomorrow for a toggle switch for sure.
    Steve
    Miller Dialarc 250
    Lincoln Ranger250
    Longevity TigWeld 200DX

  8. #8
    Made the mod to my machine today installing a toggle switch to my pedal. This simple little mod makes a good machine even better. Nice to be able to see the amp range your machine is set at before dropping your hood. Thanks again Alta Racer!
    Steve
    Miller Dialarc 250
    Lincoln Ranger250
    Longevity TigWeld 200DX

  9. #9
    I know this is a post from early last year but my pedal is not working correctly either. I tried to call tech support and the guy was already on another call and it was getting near the end of their shift so I was informed to leave a number and they would call me back Monday...which sucks because today is Friday. Any way all I needed was a direction in which way to go as far as replacing pots..its only two in the pedal so from what was posted above and from the pics I would say its the pot connected to the pedal and not the hand knob that adjust for max amp out put. This is an excellent post because that foot pedal looks exactly like mine inside and out I have a 160PI. Will probably try this mod....Longevity only warranty's their foot pedals for 6 mos. I am just hoping I can find another pot with the correct ratings.

  10. #10
    Hi Merklife and welcome to the forum. We like pictures here so please include some showing your work. Be sure to post a bit about yourself in the introduce yourself section so we can get to know you. Also, consider entering the latest contest here. The odds of winning are great.
    Dan
    Units owned Longevity PROmts 200

    Force Cut LP80 plasma cutter
    Longevity auto dark welding helmet

    Atlas 10x36" lathe
    Craftsman 5HP 30 Gal compressor
    Home made CNC router/plasma/hot wire foam cutting, 3D printing table powered by Longevity Force Cut LP80
    Home built aluminum foundry, HF 4x6 bandsaw

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