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Syncrowave 250 no output - need higher res schematic

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  • Syncrowave 250 no output - need higher res schematic

    Hello everyone,

    I'm troubleshooting a Syncrowave 250 Serial# KA814606 with no output (including HF).

    Input jumpers set for 230v. (My shop current is 246v)
    Relay CR1 activates upon main power on
    Relay CR2 & gas only activates ONLY via slide remote on TIG torch while in remote mode (I don't have a foot pedal). Panel mode does not activate CR2 or gas.
    Relay CR5 won't activate at all. (Receiving -24vdc but circuit left open by board. But relay works if I ground the circuit))

    Toggle switches test out good.
    No pre flow or spot options.

    PC1 (board) input voltages are correct but not output so I suspect the board is faulty and would like to fix it myself but need a higher resolution circuit diagram from the Owner's manual than what Miller offers on their site. (OM-353C pgs. 26-27)

    PC1 pinout voltages that differ drastically from the tech manual specs are:

    RC55 Pin 3: -.12vdcd (should be -15vdc)
    Pin 6: 14.98vdc (should be 5.8vdc)
    Pin 7: -.11vdc to 14.95vdc (should be -15vdc to 5.8vdc)
    Pin 10: 6.68vdc to .01vdc (should be 0vdc to 4vdc)

    RC54 Pin 12: 1.5vdc (should be 24vdc)

    I notice on the board voltage regulator VR1and associated cap C3 are very warm when power is on. Legs of VR1 looked a bit corroded.

    I'm not an expert at electronics but have fixed a few boards in the past. This board seems basic enough that with a little diagnostic guidance or at least a better scan of the schematic, I'm perfectly capable of swapping out suspect components. Any help would be much appreciated.

    Thanks in advance...

    Last edited by MtnMann; 01-08-2018, 07:02 PM.

  • #2
    Interesting... Just got off the phone with Miller TIG department and they said they cannot (or won't) supply me with a readable version of the schematic that is published in the Owner's Manual. I asked if I could buy a hard copy of the owner's manual and they said they would have to check and get back to me. Very frustrating.

    Does anyone have an actual Owner's Manual OM-353C?


    • #3
      Received some help via PM... Thank you!!


      • #4
        Let me know what you find out. I also have an older 250 with no output. Had the pc1 board rebuilt and still nothing.


        • #5
          Do your relays (CR1, CR2, CR5) all work when they are supposed to? Have you checked your PC1 pinouts?

          I just found a cooked capacitor C35 on my board. It's so small I didn't notice that it was cooked until just now.


          • #6
            Still looking for a readable copy of Circuit Diagram D-135 253 out of Owner's Manual OM353C if anyone can help.

            Miller did get back to me and said I could buy a hard copy. I find it very frustrating that they post an unreadable copy on the website but won't supply a readable version.


            • #7
              You can get OM-353 here:


              Not sure if that gets you any closer...see page 29


              • #8
                Well that is a better version of the general circuit diagram so that is easier to read than the one on Miller’'s site – so thanks. But it’’'s not the PC1 schematic which is the one I am looking for (from OM-353C). I was, however, able to use the one from the 2000 manual and manually edit it by comparing it to my PC1. They only changed a few things on the board so I think I have enough now to trace the faulty circuits and replace components. We’'’ll see how it goes.

                Thanks for your help!
                Last edited by MtnMann; 01-10-2018, 08:48 AM.


                • #9
                  I was able to compose a schematic combining a good version of a later one with the unreadable one off Miller's site that's in the owner's manual for this machine (later ones are only found in the Tech Manuals). I circled and crossed out components not found on my board and drew in ones that are not on the later schematic. I'm not the most proficient at electronics so I could use a little help from anyone willing to look over the schematic and advise me on what I should be replacing. C35 is obviously cooked (lower center of board to the right of IC). I ordered a bunch of components that I see being related to that capacitor as well as the -15vdc power that seems to be having an issue due to several bad pinout readings:

                  RC55 Pin 3: -.12vdcd (should be -15vdc)
                  Pin 6: 14.98vdc (should be 5.8vdc)
                  Pin 7: -.11vdc to 14.95vdc (should be -15vdc to 5.8vdc)
                  Pin 10: 6.68vdc to .01vdc (should be 0vdc to 4vdc)

                  RC54 Pin 12: 1.5vdc (should be 24vdc)

                  VR1 legs look like they've gotten hot and it runs very warm along with C3 (big black cap by VR1 at left upper edge of board)

                  I ordered new VR1 (and VR2 just in case), SR1, A1-4, U1, U2, pretty much all capacitors, a bunch of diodes, resistors, and transistors that I see along related circuit paths.

                  I had trouble identifying the two mosfets (Q1,8) that are called out as N-channel 9A 50V. Markings are:

                  I(followed by a diode symbol)R9006
                  90 1Q

                  The closest I found was an N 15A 50V. Not even sure I need to replace one or both of those but I ordered some.

                  Any guidance would be much appreciated as far as a list of most likely components to swap out...



                  • #10
                    I have a sync wave 250 an older one it quit once I found some bolts on the wireing came loose the second time it quit it was the remote contactor test the machine using a stick weld with switch on the panel if all works then trouble shoot the output contactor I had my machine since 1989 purchased new I been an electronic tech for 30 years most of the older stuff is easy to fix don't sweet the voltages some are pot setting related


                    • #11

                      I replaced a few components on the board and she's working fine now... Cost about $5 in parts.
                      These older boards are really quite simple and components re cheap!