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Synchrowave 300 need help

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  • #16
    Sorry for not responding sooner Steve. Pages 23 and 26 have the relevant schematics, which look to be close for your boards, you would be the only one to confirm.
    Page 23 - is your panel ammeter tracking amp output correctly. If it is, then your Hall sensor is ok. If it isn't, then it could be your hall sensor, the opamp (triangle in the middle) or a bad capacitor/resistor. Check component values (pins 7 and 4, 7 and ground, 4 and ground should not show a short). You have a lot of parallel circuits, so your resistor readings may not be exact. Opens and shorts, or low values (singles, tens, maybe hundreds of ohms) would be worth further checking. You should have resistances across the hall sensor blue/yellow wires and red/black wires (shouldn't be open or shorted)

    Page 26 - I wrote on some other Sync 300 thread how that circuit works, but it's tough to go from writing to schematic. If I get a chance, I will try to draw out the major blocks on that schematic. Either way, since you're getting full amperage on Hi, I would first check the part of the circuit that compares the current you want to the current you're actually seeing. That all happens at IC5, pin 2. They're basically all added together. The signal flowing through resistor R51 is your reference current set at the panel/pedal. It will be negative, so check that it is not shorted to ground. Check resistance on pins 12,20-23 against IC5 pin 2 .Check those against pins 4 and 7 too (these should be very high resistance). I will see when I can print out the schematics and component values to get close to what you should be measuring. This circuit board doesn't flow too much current except for the right side and bottom left of the schematic, so the resistances from the signal pins should not be in the tens or lower.

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    • #17
      I am just very glad to have you you helping me. I will check what you have mentioned to the best of my ability and then Im sure I will have some more questions.

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      • #18
        ok 7 and 4 my multimeter just counts down. 4 and ground do the same as 7 and 4. 7 and ground show continuity. also I havent any amp gauge. r51 shows a value of 8.89. I have to log out now I will get back.

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        • #19
          Hello John,
          I have to ask you to be patient as this may take me a while. I am checking everything you've mentioned and more I will let you know what I get soon.

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          • #20
            Steve, no worries. Looking back on it, you're really looking for the components that are causing the SCRs to fire full tilt. When you originally measured the low resistance on the current feedback circuit up above, was the hall device/board plugged in?

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            • #21
              yes it was.

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              • #22
                Ok, that seems like a low value. Hopefully this picture is legible on screen. I traced out the signals and component values. IC5 is your negative feedback error amplifier. All of those signals (23-12 across the top middle) are either a reference current value or the measured current from your hall device. With the hall device unplugged, you should get somewhere around 4k - 6k ohms (it has a potentiometer in series probably used for calibration). If you're not getting a good voltage from your hall device, then that will keep your welder at full tilt.

                Also, it's worth checking your the amplifier on your hall device. First check resistance across the blue and yellow wire, then across the red and black wires, then across pin 6 and ground.

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