Announcement

Collapse
No announcement yet.

Need Hobart TR-250-HF repair advice

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Need Hobart TR-250-HF repair advice

    I'm picking up a hobart tig tomorrow, it's an older model, here's what the guy has to say about it.

    "The Machine is a good unit, just needs a little love. I dont know exactly what's wrong with it. The current control circuit has a problem. I fixed a post flow problem a few weeks ago with a ten cent tranststor, so it could be as simple as that. The transformers, high frec. and all the major componets are good, and the unit will weld on a set voltage you just can't adjust the heat. If the price is rite I will let it go with the cables and all. It has a new Weldcraft WP17, 150 amp air cooled torch, new #2 copper ground lead. I have all the schematics and drawings for the machine as well."

    I'll have it tomorrow night, where would you start?? Is it worth trying to repair or do you think it's worth paying someone? I'm a compitent welder with mig/arc/gas and I was trained in tig many yrs ago, we used to train trying to weld soda cans together. I'm somewhat compitent is electrics as well so tearing it down isn't a prob.

    Thanks Phill

    HAHA just found out it's a guy on the board thats selling it. Small world I guess.
    Last edited by ponyracer; 11-01-2007, 08:56 PM.

  • #2
    If the unit is stuck at one amperage output, I would suggest checking the tranistor heatsink assembly. There are 5 transisitors on there. Make sure they are not shorted, especially if the unit is at max current on each range. If at minimum then check the 4 resistors on the side to see if they are open.

    Keith

    Comment


    • #3
      Yes it welds at max output on each range. Pardon my ignorance but how does one check transistors and where are they located in this machine??

      Thanks for the response.

      Comment


      • #4
        Originally posted by Hobart Expert Keith View Post
        If the unit is stuck at one amperage output, I would suggest checking the tranistor heatsink assembly. There are 5 transisitors on there. Make sure they are not shorted, especially if the unit is at max current on each range. If at minimum then check the 4 resistors on the side to see if they are open.

        Keith
        I hope I am able to open this thread up again. I have this problem with the amperage being on the low side. Last time we were on the high side, replaced the 5 transistors and all was good. Now we are on the low side as I mentioned, assuming the 4 resistors are the square shaped ones all together shown in the photo.

        the Click image for larger version

Name:	image.jpg
Views:	152
Size:	51.9 KB
ID:	703994

        Comment


        • #5
          You are correct. Make sure these are not electrically open. The bottom side is common.

          Comment


          • #6
            Any ideas on these parts? Or maybe a retrofit?

            Comment


            • #7
              Hobart no longer has parts for this machine. The transistors are I believe 2N3055 and 2N6055 and the resistors can be replaced with 0.8 ohm 20 watt resistors. You should be able to get these or something close at www.digikey.com

              Comment


              • #8
                The actual part is a fused resistor (fusistor). Will just a standard resistor actually work without fusing the circuit?

                Comment


                • #9
                  You can use a .8 ohm 20 watt resistor that is non-fused.

                  Comment


                  • #10
                    How would a 1 ohm 20 watt affect performance? Or would it even work?

                    Comment


                    • #11
                      May affect high end current output do to lower bias voltage to the control coil in the reactor. But otherwise it will be fine.

                      Comment


                      • #12
                        Keith,

                        Thanks for your help thus far, good to have someone to offer guidance. At this point I would just like a thumbs up or down on the parts in the photo. Not sure what the “J” after the resistance means but I assume these should work.

                        Comment


                        • #13
                          Those will work.

                          Comment


                          • #14
                            They did, I installed them on Sunday. Leads were a bit short, small issue. I really appreciate you taking the time to answer questions on such an old machine it was such a huge help.

                            Comment

                            Working...
                            X