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  • Syncro 250 issues

    Serial KG033217. Went to weld tig dc- today. Flip switch on and fan comes on fine, no issues then I push the pedal to start welding and CR5 relay chatters, shop lights blink like a dead short and no arc. Fan also slows. Pull cover and blow out, average amount of dirt, nothing horrendous. Try again, same thing. Check high freq points, all ok there, clean and gapped. Mess with the chattering relay and no change. Gas solenoid working, nothing visible during a quick look. Tried it on ac, hold torch in air no relay chatter, no shop lights blinking, all seems well until I try welding ac, seems like full power. Dc + same as dc -, just hold torch in mid air and push pedal, fan slows slightly, shop lights blink, no arc, hear chattering noise. I did check input power to back of machine and all is good. 120 each leg and 240 leg to leg. Worked fine last time I used it a few days ago to weld aluminum. Today not at all. Where do I go from here? Don't know much about electronics but do know I need it working. Thanks.
    Last edited by MMW; 07-23-2019, 04:09 PM.
    MM250
    Trailblazer 250g
    22a feeder
    Lincoln ac/dc 225
    Victor O/A
    MM200 black face
    Whitney 30 ton hydraulic punch
    Lown 1/8x 36" power roller
    Arco roto-phase model M
    Vectrax 7x12 band saw
    Miller spectrum 875
    30a spoolgun w/wc-24
    Syncrowave 250
    RCCS-14

  • #2
    I think your relay / High output switches that are chattering is where I would start.........they work and then the points get bad and no work.........pull the plug get the cover off locate the switches coming in from the power cord and see if they show any signs of heat..

    Comment


    • #3
      Just to be clear the CR5 relay chatters only on dc + and dc-. When on ac all three relays work fine, no chattering, they just pull in like they should. Cover is off and I can watch them work.
      MM250
      Trailblazer 250g
      22a feeder
      Lincoln ac/dc 225
      Victor O/A
      MM200 black face
      Whitney 30 ton hydraulic punch
      Lown 1/8x 36" power roller
      Arco roto-phase model M
      Vectrax 7x12 band saw
      Miller spectrum 875
      30a spoolgun w/wc-24
      Syncrowave 250
      RCCS-14

      Comment


      • #4

        Sounds bad. Try this.
        Clean AC/DC+ - selector contacts
        Check for loose fasteners/connections inside the unit.

        Comment


        • #5
          Hard to tell what's with CR5 since the PC board that drives it is just a block on the schematic. However, if the shop lights are dimming, something is drawing a LOT of current when it shouldn't be. That would lead me to suspect you have a shorted SCR (top left side of the schematic just to the right of the power input/transformer). Those are not in the circuit when you use AC, only on DC, so it would account for your symptoms. I've never seen the inside of a Sync 250, only looked at the pics in the manual, so I'm not a lot of help in the physical part of troubleshooting. Look up"how to test scr" on google. unfortunately it relates to little low-power SCRs. The operating principle is identical, but you would have to do some digging to find which connection is which for the anode, cathode, and gate.
          This link

          https://www.hdrpower.com/-/media/ame...scrs.pdf?la=en

          has some generic info on the hockey puck type SCRs used in your machine, and indicates to me that removing them and mounting them again is not for the uninitiated; I have never personally changed one and would be doing a lot of reading, searching and talking to people before I attempted it. They are not cheap, and I know just enough about mounting them to know I would really need to proceed with caution.


          Maybe one of the welder techs will see this thread and respond. It may not be very difficult to disconnect the SCRs enough to test them, but I'm not the guy to say it is or isn't.

          It is also possible there is a failure in the main PC board that is commanding one or more SCRS continuously "ON" instead of modulating the gate voltage to control the current as it should, but you and I have no visibility into the internal workings of the board. A good troubleshooter with an oscilloscope could figure that out pretty quickly by looking at the gating waveforms. Anyone ;you know have an oscilloscope and know how to use it?

          Comment


          • #6
            Spoke to repair center today and tech said it sounds like the bridge rectifier. I will probably do visual on it this weekend. He said his lead time is about two weeks. Looking up the part number 114921 it is obsolete, superseded by 181106 also obsolete. Is this an expensive part if found? Can a bridge rectifier be repaired?

            Is there a simple way to test it with a volt/amp meter?
            Last edited by MMW; 07-25-2019, 08:30 PM.
            MM250
            Trailblazer 250g
            22a feeder
            Lincoln ac/dc 225
            Victor O/A
            MM200 black face
            Whitney 30 ton hydraulic punch
            Lown 1/8x 36" power roller
            Arco roto-phase model M
            Vectrax 7x12 band saw
            Miller spectrum 875
            30a spoolgun w/wc-24
            Syncrowave 250
            RCCS-14

            Comment


            • #7
              Couple years ago I called miller tech support and talked to a guy, Jeff I think, and he recommended I replace my diode bridge doofloppies, even though they were working, because they have a life span. It’s a 1974 machine, parts are obsolete for it as well. Anyway, he said it’s really not hard to retrofit a newer model diode thingy into my machine when I’m ready to do provided it’s correctly rated for the application.

              He might have given me some part numbers, so I’ll look when I get home tomorrow. I may not have even worried about it since I don’t like to break things that aren’t broken, but I will check.

              Comment


              • #8
                That is the assembly (SR1) I was talking about in post #5 of this thread--he confirmed my suspicions. BUT, there are other bridge rectifiers in this machine (SR2, SR3), which are MUCH less expensive, so let's be sure he and we are talking about the same thing. I really don't believe either of the cheaper ones would be causing your problem, but lets be sure. I'm 99% sure we are on the same page, but always good to leave no doubt.

                Did he give you that part number, or did you find it by looking up "bridge rectifier" in the parts list? Just to be "triple positive", I would call him back and confirm the part number of the bridge rectifier he's talking about and ask for a current part number. I don't know, but I wouldn't be surprised if that assembly is $600-700. Hope I'm wrong. If you look at the parts list for that assembly on page 24 of the manual, you can see the individual SCRs that are the heart of the rectifier assembly, which is where I suspect your problem is. However, as I said before, I'd sure want to see the gate drive signals on a scope before I sunk that much money into it and found the SCRs were OK after all, and the problem is a stuck gate drive from the PC board. Miller4less has them (115114) for $153 each, times 4. Those are the parts I was talking about in the earlier post. If one is shorted, you should be able to find it by testing with an ohmmeter. My major concern is taking the bridge assembly apart and getting it back together correctly. I would probably try it if it were my machine, with great caution. I've been fixing electronics stuff worth from five bucks to millions for 50+ years, but have absolutely NO experience with hockey puck SCR mounting. Thus, I am not confident enough of the potential pitfalls to recommend someone trying it. Read the link in my previous post if you haven't already to understand why. Questions like, what is the torque spec to ensure adequate contact without crushing the SCR and yet ensuring good heat transfer; do they need silicon heat sink compound (I'd assume they do), which terminals are the cathode, anode, and gate; from field experience, if you find one shorted, is it logical to replace all 4, or can you just replace the shorted one? Questions I cannot positively answer, and I sure don't want to be one of those "fools rushing in....."

                Where are you located?
                Last edited by Aeronca41; 07-25-2019, 09:39 PM.

                Comment


                • #9
                  I am probably taking it into the repair place on Monday. I really don't have time or knowledge to mess with it although I will take a look this weekend to see if anything is visual just because I am curious. When I talked to the tech he asked the symptoms and then said it sounds like the rectifier. That was the extent of it. I went into the manual and looked up the part number, then proceeded to Miller4less. Located in north New Jersey along rt. 80. Thank you for all the info. Just thinking now about what I am willing to spend to fix it vs. buying another because once diagnosed a decision needs to be made. Not a hobby machine so I need it up and running. I will post any updates.
                  MM250
                  Trailblazer 250g
                  22a feeder
                  Lincoln ac/dc 225
                  Victor O/A
                  MM200 black face
                  Whitney 30 ton hydraulic punch
                  Lown 1/8x 36" power roller
                  Arco roto-phase model M
                  Vectrax 7x12 band saw
                  Miller spectrum 875
                  30a spoolgun w/wc-24
                  Syncrowave 250
                  RCCS-14

                  Comment


                  • #10
                    Sounds like a wise choice, especially since you need this thing working -- certainly not the same as messing around with a hobby machine. You're too far away for me to offer to take a look at it. I'm in upstate NY. Just asked in case you might be a half hour or so away. Good luck! Anxious to see how this comes out.

                    Comment


                    • #11
                      Got a call today from the repair center. It is terminal. Rectifier no good and unavailable. He could replace one of the three(?) but it also has an issue with it on ac it only is max amps which is another part that is unavailable also. He search a few places plus the internet and turned up nothing. I am sad and now need to replace this machine. I have a lead on one but waiting for the guy to get back to me. As soon as it broke I reached out to him about selling his that he does not use at all and he said he would think about it. E-mailed him today telling him I want it and have not heard back yet. I will let you know the exact issues when I pick it up later this week.
                      MM250
                      Trailblazer 250g
                      22a feeder
                      Lincoln ac/dc 225
                      Victor O/A
                      MM200 black face
                      Whitney 30 ton hydraulic punch
                      Lown 1/8x 36" power roller
                      Arco roto-phase model M
                      Vectrax 7x12 band saw
                      Miller spectrum 875
                      30a spoolgun w/wc-24
                      Syncrowave 250
                      RCCS-14

                      Comment


                      • #12
                        That sucks.

                        Comment


                        • #13
                          Found a dialarc HF for sale. Would I be happy with this to replace a syncrowave? I know it has a little less duty cycle and it has been mentioned on here that it is not square wave so it welds a little different. I can always get it for a temporary machine until I find another Syncro but it is even worth doing that?
                          MM250
                          Trailblazer 250g
                          22a feeder
                          Lincoln ac/dc 225
                          Victor O/A
                          MM200 black face
                          Whitney 30 ton hydraulic punch
                          Lown 1/8x 36" power roller
                          Arco roto-phase model M
                          Vectrax 7x12 band saw
                          Miller spectrum 875
                          30a spoolgun w/wc-24
                          Syncrowave 250
                          RCCS-14

                          Comment


                          • #14
                            Welding carbon and stainless on DC you probably won't notice much difference. AC Aluminum, you'll notice the difference. If the end game is Aluminum, my guess is you will be disappointed having tasted the square wave fruit. Just curious, how decked out is the Dial Arc? It could still be a good deal if it has some bells and whistles besides just AC/DC and HF.

                            As far as fixing the Syncrowave, if you don't and it has volt amp meters...well I'd be interested in them. Dibs.

                            Comment


                            • #15
                              If the price is right, even with all my machines now, I’d still pop on one.

                              Those are big, transformer machines that have a solid history of enduring a lot of punishment and keep on choochin. Probably doesn’t have all the functions your sycrowave had.

                              Provided it’s in working order and the price is right, you need a machine right? If we were close, I’d loan you one of mine.

                              Comment

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