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Synchrowave 350 from 1992 needs a small main circuit board repair

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  • Synchrowave 350 from 1992 needs a small main circuit board repair

    My trusty Synchrowave 350, S/N is KA782001, I bought in 1992, has had a control problem for some time. I can no longer tell what the preset amperage is set at. When I push the spring-loaded toggle switch down to change from displaying actual amps to display the maximum amperage set by the dial, the display goes blank.

    I had the repair guy out from one of my local welding supply haunts to evaluate the problem. In short order, he pronounced the problem as a bad main circuit board. The machine needs a new main circuit board, or someone to repair the existing board. The part number for my circuit board is 119614, and has been superseded twice to 129612 and 148371. The repairman told me in 2017 that a P/N 148371 board would be about $825, and that's a friend price, plus labor. I didn't have the cash to spend then on fixing the welder, so I just lived without being able to accurately preset the maximum current.

    Now I'm confronting a host of light-gauge stainless repairs over the coming winter for a friend's swimming pool filtration equipment. Chloride corrosion pitting damage on the filter's thin 316 stainless material demands I have my max amps just right or it will melt through. Surprise - now I find I can no longer get the circuit board from Miller. Several places on the web have a $250-$350 flat rate repair available, but the repair guy tells me most likely only one discrete component on the board has failed. I hate the idea of coughing up $300 for a single resistor.

    Does anybody on the Miller Forum do simple circuit board repairs for a reasonable charge?

  • #2
    Could you just strike an arc on a big steel block at 100%, read the current on the display, adjust accordingly, repeat until you get it set where you want? Kind of a make-do solution, but better than hoping you're at 20A and actually being at 40A and blowing a hole in it.

    Comment


    • #3
      Some board repair houses I've bookmarked (don't know anything about any of them):

      https://www.innovatcorp.com
      http://www.industrialelectronics.com
      http://www.pwt-online.com/services/servPCBT.htm
      http://www.weldtron.com
      http://www.plccenter.com/en-US/Services/Repair
      http://gemelectronics.org
      http://www.yorkelectronics.com

      Good luck. That's a bummer. Did you search ebay for your board?

      Comment


      • #4
        I have used InnovatCorp and Radwell with good service. It would be even more frustrating if the board wasn't the problem. Your owners manual actually has the wiring diagram and schematics, so it wouldn't be too difficult to find the issue. My first check would be switch S2 to make sure the toggle switch actually closes, then I would check relay CR3 to make sure it has 24VAC across it when you toggle switch S2, and to make sure the relay actually closes when you put 24VAC across it. If that checks out, then I would look at the boards.

        The numbers are hard to read on the schematic, but I will see if I can give you a list of components to check (or have someone check).
        Last edited by jjohn76; 10-02-2019, 01:12 PM.

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        • #5
          Originally posted by jjohn76 View Post
          I have used InnovatCorp and Radwell with good service. It would be even more frustrating if the board wasn't the problem. Your owners manual actually has the wiring diagram and schematics, so it wouldn't be too difficult to find the issue. My first check would be switch S2 to make sure the toggle switch actually closes, then I would check relay CR3 to make sure it has 24VAC across it when you toggle switch S2, and to make sure the relay actually closes when you put 24VAC across it. If that checks out, then I would look at the boards.

          The numbers are hard to read on the schematic, but I will see if I can give you a list of components to check (or have someone check).
          Thank you for the advice and the offer of the component list to check.

          I watched while the tech from Matheson Gas's repair shop did exactly the switch continuity tests you describe; switch was okay. He then metered the output signal from the board... not okay.

          Both InnovatCorp and Radwell had flat-rate prices. The guys I spoke with would not talk time and materials for repairing small/simple defects. Big bucks.

          Comment


          • #6
            Originally posted by Fix Until Broke View Post
            Could you just strike an arc on a big steel block at 100%, read the current on the display, adjust accordingly, repeat until you get it set where you want? Kind of a make-do solution, but better than hoping you're at 20A and actually being at 40A and blowing a hole in it.
            I have a block of 3/8" copper bus bar stock for a strike plate. It works, but I would really like to have the full functionality of the machine restored. My Synchrowave 350 is a great welder, I just need to get it the TLC it needs. I'm ashamed to admit neglecting it for a number of years; the little problems have become a big annoyance now that I need to do a lot of work with it. One of the big reasons I bought a 350 over a Synchrowave 250 in 1992 was the 350 could dial down to much lower amp outputs for fine work.

            Comment


            • #7
              Originally posted by jpcallan View Post

              I have a block of 3/8" copper bus bar stock for a strike plate. It works, but I would really like to have the full functionality of the machine restored. My Synchrowave 350 is a great welder, I just need to get it the TLC it needs. I'm ashamed to admit neglecting it for a number of years; the little problems have become a big annoyance now that I need to do a lot of work with it. One of the big reasons I bought a 350 over a Synchrowave 250 in 1992 was the 350 could dial down to much lower amp outputs for fine work.
              Agreed on having the full functionality of the machine - just a possible solution if you needed to use it ASAP.

              Interesting to know about the 350 having better fine control over the 250. I've struggled with fine welding work (A/C Condenser finned tubes) on my 250. Once an arc is established I can run it down in the single digit amps just fine, but the initial startup must be 30-40 amps for a few hundred milliseconds which will blow a hole in stuff this thin. I put a small piece of 1/8" flat nearby to start the arc on, lower the current and then move over to the thin tube.

              Anyway, enough of my dribble. I can understand why the shops do a flat rate price. Presumably they've reverse engineered these and know what fails and what does not, and what is likely to fail, so they get a used one in and just fix everything. It's more expensive, but you're a happy customer because the part works instead of working for now, then something else going wrong in 9 months and now you're blaming them. But unless you're wiling/able to reverse engineer it yourself, it might be the best option. Probably worth it to inquire about warranty from these guys.

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              • #8
                Ok, so it looks like he checked either pins 1 and 5 on Plug 50 or pin 4 on plug 52. Given that the display goes blank, I am assuming it is Pin 1 on Plug 50 from PC1. Does that sound about right? If it is, then I would say it is either the quad opamp A55 , or the resistors that connect to lead 12 on that chip. If you see any corrosion on the leads for that chip, that chip would be my bet. It's an LM324. Not too long ago I repaired a Miller Spectrum 2050 that had a continually open gas solenoid because an inverting op amp had a corroded lead.
                Last edited by jjohn76; 10-02-2019, 05:22 PM.

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                • #9
                  Originally posted by jjohn76 View Post
                  Ok, so it looks like he checked either pins 1 and 5 on Plug 50 or pin 4 on plug 52. Given that the display goes blank, I am assuming it is Pin 1 on Plug 50 from PC1. Does that sound about right? If it is, then I would say it is either the quad opamp A55 , or the resistors that connect to lead 12 on that chip. If you see any corrosion on the leads for that chip, that chip would be my bet. It's an LM324. Not too long ago I repaired a Miller Spectrum 2050 that had a continually open gas solenoid because an inverting op amp had a corroded lead.
                  These are excellent suggestions - thank you.

                  My local welding supply obtained a PDF file of the service manual from Miller. I just picked up my hardcopy of the Synchrowave 350 Technical Manual last night after having my nearby FedEx Office print and bind it. Now having up to date main board schematics for my serial number, I'm almost ready to do battle.

                  The welder is sandwiched in between a whole lot of other gear, so digging it out and reopening the left-hand side cover will have to wait until my wife gets back from visiting relatives next week. The top of the welder got unburried when I fixed the nonoperational OFF button (with much help and guidance from this forum), so half the excavation job is done.

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                  • #10
                    Sounds good. I don't have access to the technical manual, but the operator manual surprisingly had the board schematics in it as well. The numbers are tough to read, so hopefully the tech manual is a bit more legible. Once you find chip A55, measure voltage across pins 12 and 11 which should match the voltage across pins 13 and 11. If neither show voltage, check R47. If neither side of R47 is showing voltage, then there is a break between connector RC50-2 and R47. Otherwise, just looking at the schematic, you would have a lot of other major problems too. Hopefully this helps. Here's a picture of an LM324 with pin locations for reference. The opmanual says A55 is a LM324, but I would recommend you scratch the coating of the chip with your finger nail just to make sure. Click image for larger version

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                    • #11
                      Originally posted by Fix Until Broke View Post

                      Interesting to know about the 350 having better fine control over the 250. I've struggled with fine welding work (A/C Condenser finned tubes) on my 250. Once an arc is established I can run it down in the single digit amps just fine, but the initial startup must be 30-40 amps for a few hundred milliseconds which will blow a hole in stuff this thin. I put a small piece of 1/8" flat nearby to start the arc on, lower the current and then move over to the thin tube.

                      Anyway, enough of my dribble...
                      Not dribble at all! I'm interested in what you had to say about welding thin materials. When I bought my machine in 1992, I had the same experience with the Synchrowave 250 you have, but I was too green to appreciate all the subtleties; I just somehow liked the Synchrowave 350's arc behavior better and the specs in the Miller brochures were pretty clear about the difference in low amp performance. I doubt I have ever had my Synchrowave 350 over 200 amps; it's powered by a 40 amp breaker, not the 100 amp breaker the manual recommends.

                      It didn't occur to me to use a run-off (run-on?) strip to start a weld, then reduce the amps; clever idea. I've used a run-off strip at the end of a weld to leave the crater on the strip, but never thought of starting that same way.

                      I have a small side business doing stainless counters/sinks, A-C and refrigeration work (mostly for small restaurants), and particularly enjoy it when I get to fix an aluminum coil on an evaporator or condensing unit that the mainstream competition declares is unrepairable. For light field work, I have a Maxstar 91 with Snap-Start box and an early Dynasty 200. Both machines are good on light DC work, but the Dynasty 200 has really lovely low amp arc characteristics. In fairness, the whole range of amperages on the Dynasty 200 are a pleasure, that goes double in AC mode with frequencies above 60 Hz available.

                      If you will permit a digression, have you ever tried Lucas-Milhaupt's AL822 flux-cored solder for repairing aluminum A/C tubing? The stuff works great compared to all the stuff I've tried over the years that came before it. If your curious,
                      see: https://www.youtube.com/watch?v=UqPxjH-hWIA&t=16s
                      It's also sold under the name Handy-One AL822. It's sometimes hard to find and always expensive, but works truly well.
                      Last edited by jpcallan; 10-02-2019, 07:17 PM. Reason: Spelling

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                      • #12
                        jpcallan - Thanks for the tip on the AL822. I've tried some similar stuff recently that's not supposed to require flux and it kind of worked, but need some more time/practice with it. I'll see if I can get some AL822 on the way for future projects.

                        I didn't choose the 250 so much as it was what I stumbled upon for a good price and I wanted a TIG welder so truly an uneducated decision. For the most part I've been very happy with it. Some of the new inverter functions look cool and a smaller machine would be nice, but I just do hobby work for myself and friends so no need to invest in something new.

                        I end up fixing quite a few air conditioning lines for rear cooling on things like suburbans and such that leak or corrode away. They get something like $650 for a new line so sometimes I can weld them up. Those are pretty easy at about 0.050" thick tube. Did a condenser for a friend who stuck a wrench through a brand new one while installing it. Was right in the middle of the finned area. Broke out the 0.040" tungsten and the smallest filler I had and was able to patch it up and it held. VERY tedious work - not only did I have to use a run-on strip to start the arc, I had to start depositing filler away from the hole and work my way over/around the hole and then fill it over. The fins were conducting so much heat away it was hard to get it just right where there was a puddle, but not blow it out on the edge. I ended up removing a few extra fins which helped a lot.

                        On DC it seems to work well with less (but still more than I'd like) current overshoot on startup compared to A/C - I can stitch 0.030 filler wire together without having a big ball at the joint - just warm it up and push it together. I should try it with lift arc/touch start instead of high frequency start - I wonder if that's what is causing the overshoot on arc initiation?

                        Sorry, I keep dragging this off topic - I hope you are able to get to the bottom of your current display issue and it's a repair you can execute yourself!
                        is there any way we could host the .pdf of the service manual here so others could benefit from that info?

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                        • #13
                          For what it's worth, I have had luck finding some older Miller technical manuals on the Red-d-Arc website under Resources -> Product Resources -> Spec Sheets and Manuals. There is a technical manual for the little later model Syncrowave 250DX and 350LX.

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                          • #14
                            Thanks - Unfortunately those are a generation newer than mine, but the panel looks almost identical so maybe there's some common parts. One of those things where I hope I never need to use it, but would like to have it just in case.

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                            • #15
                              Since you guys strayed....I’ve used some similar stuff to that brazing rod, but not the flux cored stuff. I’m interested in checking it out.

                              On the low amp AC tig arc starts, the ability to increase the freq is a big help. My guess is the focusing of the arc helps reign in the arc wander and gets it off straighter and faster. I also dress my tungsten down closer to something I’d use on DC, if it’s thin metal, and run the balance up around 80 % EN. I’ll also jam my filler rod in there and light off on that instead of blowing a gaping hole in an evaporator line or something similar. I just did a repair on a Kubota tractor evaporator coil. Anything that says kubota on it is expensive. They’re very proud of their stuff.

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