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Thread: Older Syncrowave 300 pedal issues

  1. #1
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    Older Syncrowave 300 pedal issues

    I just set up an older (1979 I believe) Syncrowave 300 serial #HK234xxx itís got a 5 pin pedal. The pedal is a Thermadyne Therma Arc serial: R809 69A I8313.

    I just finished getting the welder wired in on a 100 amp circuit and fired it up for the first time yesterday. The pedal seems to be acting as an on/off switch only with no amperage control. Gas does cycle on and off and post flow as it should, everything else seems to function but I have no amperage control.

    I have the ďcontactorĒ switch set to remote as well as the ďcurrentĒ switch. It does have an SP-4 programmer but I have that turned off.

    I am trying to determine if I have a machine issue or a pedal issue. Is there a way to ohm out a couple pins on the pedal and see if itís working? Or any other tests to pedal or machine I can perform?

    I did a quick aluminum weld and it appears to weld very nicely except for the fact I have no current control....

  2. #2
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    Re: Older Syncrowave 300 pedal issues

    Your foot control will have variable resistance across a couple wires.

    Use your multimeter to check for smooth change with pedal movement.

    If that works out, your switch on the panel may just not be working.

    I'm no pro at diagnostics, so this is just where I'd start.
    Dave J.

    Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~

    Syncro 350
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    Tried being normal once, didn't take....I think it was a Tuesday.

  3. #3
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    Re: Older Syncrowave 300 pedal issues

    Anyone know which two pins I tried to find a diagram but am striking out...

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    Re: Older Syncrowave 300 pedal issues

    If you haven't already found the manual it should be available here: https://www.millerwelds.com/support/manuals-and-parts

    It looks like your machine was sometimes operated with only a start stop switch and the current control was optional. See Fig. 3-4 page 9 in 0350F_MIL.pdf . I am guessing that is your manual. Looks like pins A & B are the switch and the other 3 must be the current control if it is there. You might want to open the foot control up to see what is inside. Have fun.

    P.S.- Page 20 , Fig. 7-1 upper right of the diagram as it displays on it's side or lower right if you rotate the Fig. 90 cw.
    Last edited by Meltedmetal; 03-28-2021 at 09:11 AM.
    ---Meltedmetal

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    Re: Older Syncrowave 300 pedal issues

    Well looks like A and B are indeed on off they toggle zero and infinite resistance. Pins C and E give me smooth resistance change of ~30-1000 ohms from cracked to full pedal. Pin D seems to do nothing with any other pin? I opened up the welder and checked that the remote current switch is toggling and it appears to work as it should I cleaned up the spades anyway. Still not getting remote pedal current control though....

  6. #6
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    Re: Older Syncrowave 300 pedal issues

    Do you have current control from the panel? R-1 which I think is the panel current control looks to be 2 watt 1000 ohms. There is not much other than a couple of capacitors between the remote connection and the circuit board. Set for panel you should be able to check that you are still seeing 1000 ohms at the remote contact switch terminal and where terminal C connects to the circuit board. one or both of the caps could be shorted. D appears to be a ground connection. I don't know what Miller pedal was supposed to work with that machine and there is no circuit shown after the connection to the board. See Fig. 7-1 page 20 again.

    Caution: Machines with big capacitors like this are usually designed to bleed down the caps on their own but this safety feature can fail without affecting the operation of the machine so be careful inside there even with the supply wires disconnected as they should be unless you are taking voltage readings and are competent to do that. Just saying.
    ---Meltedmetal

  7. #7
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    Re: Older Syncrowave 300 pedal issues

    I do have current control from the panel if by that you mean can I move the big dial and change my amperage. This does work but as soon as I hit the pedal Iím at full for whatever the dial is set to. I have figured out if I turn crater fill on I can use this as a way to vary my output tap pedal when it starts getting too hot let off and crater fill slowly ramps down then another tap to ramp up etc. Itís not ideal but it let me get one job done today while I figure out this pedal issue.

    The pedal says on it 2 watt 1000 ohm so I hope itís compatible. There are a couple small dime size capacitors right on the back side of the remote hook up port when I take the side cover off.

    ďcheck that you are still seeing 1000 ohms at the remote contact switch terminal and where terminal C connects to the circuit board.Ē Iím not quite sure where exactly to check for these readings? Itís pretty difficult to trace the wire back from terminal C to the circuit board as everything is black wire and tied together.

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    Re: Older Syncrowave 300 pedal issues

    Ok update: I chased around the wires which are all black but at least paint labeled. Pin E is #116 which runs back to the panel/remote current toggle switch. Checked it and it tests fine for continuity all the way back to the switch.

    Pin C is #106 this goes back to the circuit board and I have continuity that far as well.

    Where would I test for ohms to 1000? If I put the multimeter across from where 106 hits the board and where to 116 at the terminal end to the switch I get a smooth reading up to 1000 there.

    There are 4 small capacitors on the back side of the pedal hookup these are Z5U .05Z 500v little button capacitors. Iím not sure how to go about testing them for shorting or functionality.

    There is also a wiring diagram taped to the inside of the side cover which is slightly different than the one on page 20. Itís listed as circuit diagram D-080 270 (page 20 is D-80 260) I donít know if this was attached by Miller and is correct or if itís something a previous owner added?

  9. #9
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    Re: Older Syncrowave 300 pedal issues

    You are fast running past my level of expertise. I see that the remote/panel switch appears to switch stuff in a few places. I had another odd thought..... Your pedal is not by any chance wired so that it comes on full and then reduces the further you push it?
    ---Meltedmetal

  10. #10
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    Re: Older Syncrowave 300 pedal issues

    I do not believe so. I ran a bead on some scrap and went back and forth from cracked to wide open and see no change in arc. I guess my next step is to trace the center wire from the switch back, I know I have connection all the way to the switch but maybe I donít have from the switch back? This was the only thought I had so far.

  11. #11
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    Re: Older Syncrowave 300 pedal issues

    Quote Originally Posted by Wardbrook View Post
    Well looks like A and B are indeed on off they toggle zero and infinite resistance. Pins C and E give me smooth resistance change of ~30-1000 ohms from cracked to full pedal. Pin D seems to do nothing with any other pin? I opened up the welder and checked that the remote current switch is toggling and it appears to work as it should I cleaned up the spades anyway. Still not getting remote pedal current control though....
    I have no experience with that brand/model of pedal, but the values should be similar to those of Miller pedals to work properly. A and B are definitely just the contactor switch so off or on is all you should get.

    I just sold the last 5-pin Miller pedal I had, so I can't double check, but I thought the resistance figures worked out the reverse from what you're saying.

    On mine from pin C to E would start at 1K and go down to 0. From D to E was the opposite and started at 0 and go to 1K. Either way, from C to E and from D to E should be opposite of one another, so that suggests a pedal issue since you're not getting anything between D and E.

    Have you opened up the pedal to take a look yet? They're pretty simple boxes and it might just be a wire that's come loose.
    Last edited by G-ManBart; 03-30-2021 at 01:05 PM.
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    Miller Syncrowave 250DX
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  12. #12
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    Re: Older Syncrowave 300 pedal issues

    If thatís the case it would certainly explain everything. I have not opened up the pedal I have to figure out how it comes apart I didnít see any obvious way unless there are screws under the grip tape surface. I will try to find the time to do that today

  13. #13
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    Re: Older Syncrowave 300 pedal issues

    Quote Originally Posted by G-ManBart View Post
    I have no experience with that brand/model of pedal, but the values should be similar to those of Miller pedals to work properly. A and B are definitely just the contactor switch so off or on is all you should get.

    I just sold the last 5-pin Miller pedal I had, so I can't double check, but I thought the resistance figures worked out the reverse from what you're saying.

    On mine from pin C to E would start at 1K and go down to 0. From D to E was the opposite and started at 0 and go to 1K. Either way, from C to E and from D to E should be opposite of one another, so that suggests a pedal issue since you're not getting anything between D and E.

    Have you opened up the pedal to take a look yet? They're pretty simple boxes and it might just be a wire that's come loose.
    Possibly if someone wired the pedal looking at the machines pin out instead of pedal pinout it may have flip flopped those and that is what you get.

  14. #14
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    Re: Older Syncrowave 300 pedal issues

    Quote Originally Posted by danielplace View Post
    Possibly if someone wired the pedal looking at the machines pin out instead of pedal pinout it may have flip flopped those and that is what you get.
    Yes, that's possible. I've gone through about ten pedals and all were wired the way I described. I made a mistake at an auction and bid on a pallet of pedals and wound up with all of them....LOL. I've been slowly selling them on eBay and have just a couple left to go to break even.
    Check out my bench vise website:
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    Miller Syncrowave 250DX
    Millermatic 350P with XR AlumaPro
    Miller Regency 200 with 22A feeder and Spoolmatic 3
    Hobart Champion Elite
    Everlast PowerTig 210EXT

  15. #15
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    Re: Older Syncrowave 300 pedal issues

    all miller foot controls are wired A and B is switch. C, D and E are the potentiometer.
    C to D should read 1000 ohms. E is the variable to C and D.
    In order to get a proper Control voltage you need to have the power supply on C and common ground on D. On a tig welder the power supply is adjustable by the main current control. This sets the max welder output so when peddle is pushed all the way down you can limit the max output to a usable level for the weld you are doing.
    On your welder I have only seen a couple set up like that.
    Looking at the SP-4 manual. turn unit power switch to off and auto/manual switch to manual for manual operation with out the SP-4 working. All control should now be at the welder. Go to millerwelds.com and you can down load the owners manual. In the owners manual are operation and installation instructions. There are three get the one for the right serial number group. you might have to put the machine diagram next to the SP-4 diagram and then connect the two using the installation instructions. You might be able to call Miller tech support and ask if there is a different diagram that shows them wired together. Ask real nice and they might send it too you. since repair centers are not allowed to give out any diagrams or service books.

  16. #16
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    Re: Older Syncrowave 300 pedal issues

    Thanks I meant to update this a couple weeks ago I moved the ground wire from the welder ground to the potentiometer empty leg from where it originally went to the pedal body. This made the pedal work but backwards aka full pedal was least power, lightly pressed was full power. Today I finally had time to relook at it I thought just swapping E and C would fix it but that turned out to not be the case and pedal function was still backwards. With some experimenting of swapping around wires to potentiometer legs I eventually got the pedal functioning as it should and ran a couple beads. Thanks to all that helped with this head scratcher!

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