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Older Hobart 175 handler no wire speed control

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  • Older Hobart 175 handler no wire speed control

    Hey guys, been googling for answers to my problem for the last 3 days, alot of topics lead here, so figured it must be a good site, so anyhow, the meat of the question followed by the background:

    I have no control of wire speed, it goes all out no matter where I set wire speed knob too.
    Hobart Handler 175
    Serial# LA298147
    Stock # 500417

    I pulled the potentiometer out, measured the ohms on it, when the knob is turned all the way left (slowest wire speed) it read 0.0ohms, when I turned it all the way clockwise, it then read 53.2ohms...given that is is a 50ohm reostat, I have to assume that this part is good?

    Now I have'nt used this welder for a few years, the other day I decided to revamp my granfathers jon boat, stripped out all the rotten wood and decided to go all aluminum for framing/decking/compartments....so after searching around, BRWelding sells a kit to adapt a spool gun to my welder, it just jumps in between the wire feed motor wires so you can switch the motor off while using the spool gun, but it still allows the gas to come through.

    Adapter I bought to convert for use with Spoolrunner 100 spool gun:
    http://www.ebay.com/itm/HOBART-HANDL...item5649aee721
    Now since my welder is older, is was'nt plug and play like this kit was designed for on the newer welders, so I had to cut the plug ends off the switch, and then cut wires going to wire speed motor so I could get the switch wiring hooked up in the middle....there really is only one way to wire it up since polarity must be correct otherwise wire roller spins in reverse, or just does'nt work at all. I confirmed all this when I called BRWelding to go over this switch addition to my older welder.

    And the spool gun I bought:
    http://www.google.com/products/catal...ed=0CG8Q8wIwAA

    Long story short, got it all wired up, hooked up spool gun with 4340 wire and 100% argon, put heat on lowest setting (the heat knob still works, just not wire feed speed) and I was able to confirm I can weld aluminum no problem.....but as we all know, you have to be able to adjust wire speed....and at this point i cannot.

    I even took the switch out I installed, put the welder back to stock, and even then there is no wire speed control, just goes full tilt all the time. Thankfully aluminum welds faster than mild steel, and it works great with heat on lowest setting and wire speed where it's at for the .125 wall aluminum square tubing I'm using....BUT, obviously before I put the sides back on the welder, I want/need/have to figure out what/where to test to figure out what is bad and why I have no wire speed control.


    Thank you for reading this far, and anxiously awaiting for any help.
    Josh

  • #2
    no speed?

    If this is one of the Miller buit machines the most likley cause is a shorted transistor on the control board. It is marked as Q1 and located at the center of the board.They have a history of failing. The transistor part number is stenceled on the unit ( you need magnifier to see it ) so you can try replacing the transistor or you can just replace the board.
    O.F.

    Comment


    • #3
      I'll check it out when I get up this afternoon, not to sound too lazy, is there a p/n for a circuit board...or can a guy just get a transitor from radio shack?

      Comment


      • #4
        Alright, I dropped the ball and let the welder sit for a bit while doing other projects, but then got back to it so figured since i hate open ended posts with no solutions, I would come back and tell the fix because I know other's have, will have this problem

        Found a few posts on other welding boards, that gave part number for the factory replacement transistor, Q1. As luck would have it, a miller/hobart tech also gave info on a BEEFIER replacement, that does require some modifications to fit/work...being the typical , bigger is better, more is more LOL, i opted for the big dog replacement that I ordered from Amazon.com:
        http://www.amazon.com/gp/product/B00...ls_o01_s00_i00

        When I recieved it yesterday, I noticed in the packaging that it is easily 2x's larger than the factory peice. I wish I would've taken pictures of the process, but I did'nt, sorry. If you go this route to fix it yourself, I'm going to have to assume your somewhat handy, so just know common sense will easily show you what needs to be done toreplace it, but I will cliff note it below:

        Used 1/8" drill bit to remove factory rivet holding factory transistor to heat sink in Q1 location.
        I had to use a jewlers straight screwdriver to pry transitor body away from heat sink..it's kinda of glued down to it.
        Was easier for me to bend factory transitor back and forth to break the body of it off the legs, leaving the legs still soldered into circuit board, then used my soldering gun to heat the back side of the factory transistor legs to melt factory solder, while pulling the legs out of the front side of the board with needle nose pliers.
        I then used a tiny drill bit to clean out the factory punched holes in circuit board where transistor legs poke through.

        Took my dremel and attached a sanding roll to it that i used for porting intake manifolds/heads for cars and sanded away the factory plastic/rubber coating over the heat sink where transistor gets riveted too. i did this to assure maximum heat disapation with metal to metal vs metal to plastic/rubber. Blew off any sanding dust with blow gun.

        then put the tiny cutting wheel attachment on the dremel and modified the legs on the NEW transistor. They start out skinny and will fit into factory holes on circuit board, but they get wider near transistor body. This wider portion will not allow the new transisitor to be pushed far enough through the circuit board so you can re-rivet the new transistor to the heat sink.

        Once i had legs all ground down/modified to be pushed further into circuit board I still have to drill a new 1/8" hole in heat sink...the new hole will be higher than the factory hole...just place the new transitor on the heat sink and use that as the guide for where to drill new hole.

        After new hole was drilled, I used a 1/8" x 1/4" steel rivet to attach new larger transistor to the heat sink.

        Turned circuit board over, used soldering gun/solder to reattach new transistor legs to circuit board contacts.

        Reinstall circuit board into machine, plug all the wiring back in, and wallah, wire speed control works like a champ!!!

        Comment


        • #5
          Your transistor was glued to heat sink with thermal grease, or other common name. It helps insure better heat transfer to heat sink. You should have used this with your new transistor. This link tells all you need to know.

          http://en.wikipedia.org/wiki/Thermal_grease

          Comment


          • #6
            I was searching around on ebay for some welder parts for my handler 135 and found a guy claiming to sell a kit for like $15 which was supposed to fix speed problems whether the wire is full speed all the time or no speed. FYI his photos make it look like he will be selling you a drop in circuit board but I have a feeling it will just be some individual components you will have to replace on the circuit board yourself. I had and older handler that had a burnt spot on my circuit board right where a component was soldered on where I could see the part was no longer making a connection. I got a decent solder gun with a relatively small tip, made sure I got flux into the hole and the solder sucked right up into place resulting in my welder once and again up and running. So I would assume removing one of those same capacitors or something that only has a couple legs to solder being relatively easy, but if it is a chip of some sort with a dozen or more legs on each side right next to each other then you might want to get some professional help since I think it might require using a solder sucker first where something with just a couple legs you could heat up with the solder gun and remove from the backside with tweezers at the same time. I have found lots of good youtube videos when it comes to soldering and circuit board work that can show you exactly what tools are required and best way to attack the problem. Good luck!

            Comment


            • #7
              Originally posted by NOKES View Post
              I was searching around on ebay for some welder parts for my handler 135 and found a guy claiming to sell a kit for like $15 which was supposed to fix speed problems whether the wire is full speed all the time or no speed. FYI his photos make it look like he will be selling you a drop in circuit board but I have a feeling it will just be some individual components you will have to replace on the circuit board yourself. I had and older handler that had a burnt spot on my circuit board right where a component was soldered on where I could see the part was no longer making a connection. I got a decent solder gun with a relatively small tip, made sure I got flux into the hole and the solder sucked right up into place resulting in my welder once and again up and running. So I would assume removing one of those same capacitors or something that only has a couple legs to solder being relatively easy, but if it is a chip of some sort with a dozen or more legs on each side right next to each other then you might want to get some professional help since I think it might require using a solder sucker first where something with just a couple legs you could heat up with the solder gun and remove from the backside with tweezers at the same time. I have found lots of good youtube videos when it comes to soldering and circuit board work that can show you exactly what tools are required and best way to attack the problem. Good luck!
              Seriously, replying to a 5 year old post?

              Dale
              Lives his life vicariously through his own self.

              Comment

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