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  1. #1
    Join Date
    Aug 2013
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    12

    Default Factory modification to a Syncrowave 250, troubleshooting help?

    I have a 1989 Syncrowave and the current adjustment knob is "compressed" so that 0 amps starts at a about 70 A dial setting. It uses the older type PC1 board. The high end is OK so that I get 300 A at the max setting. Adjusting the pots that set max and min current will not trim this out.

    It looks like the op-amp that measures the shunt had some components replaced around it with a tacked on capacitor and spade lug to ground. Someone added a third wire to the shunt also. Does anyone know if this could have been a factory mod that isn't documented? --Not sure why anyone would do this. The foot pedal in remote works fine also (0 current to max current fully depressed, no matter the dial setting).

    Any help would be appreciated. Thanks.

  2. #2
    Join Date
    Nov 2003
    Posts
    3,210

    Default

    Sounds like somebody may have accidentally installed an "Audio Taper" potentiometer during a repair... rather than the linear taper it requires ...

    just a guess...

    Cruizer may have a better answer...
    .

    *******************************************
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  3. #3
    Join Date
    Aug 2008
    Location
    Orange, TX
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    1,215

    Default

    X2 on H80N's audio pot theory.
    MM200 w/spot controller and Spoolmatic 1
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  4. #4
    Join Date
    Aug 2007
    Location
    Northern California
    Posts
    193

    Default

    Quote Originally Posted by duaneb55 View Post
    X2 on H80N's audio pot theory.
    I agree. If that is the cause, the potentiometer could be replaced with the correct linear taper potentiometer. It's likely that the original potentiometer went bad and was replaced with the wrong style. After all, a potentiometer is a potentiometer, isn't it? Not it's not.
    Miller Syncrowave 200
    Milermatic 252
    Lincoln AC/DC "Tombstone"

  5. #5
    Join Date
    Aug 2013
    Posts
    12

    Default

    Thanks everyone, I measured the voltage on the pot wiper and it is linear from zero to the max setting. But when I plotted the current output as a function of the pot position, its like the first 1/3 turn does nothing. Also, the relay, CR1, doesn't actuate at all until I get past the 1/3 turn.

  6. #6
    Join Date
    Nov 2003
    Posts
    3,210

    Default

    Still betting that somebody erroneously installed an audio taper (logarithmic) pot during a repair... rather than the needed linear taper..

    Easy enough to find out....

    the potentiometer should be marked...
    .

    *******************************************
    The more you know, The better you know, How little you know......

    “The bitterness of poor quality remains long after the sweetness of low price is forgotten”

    Buy the best tools you can afford.. Learn to use them to the best of your ability.. and take care of them...

    My Blue Stuff:
    Dynasty 350DX Tigrunner
    Dynasty 200DX
    Millermatic 350P w/25ft Alumapro & 30A
    Millermatic 200

    TONS of Non-Blue Equip, plus CNC Mill, Lathes & a Plasmacam..

  7. #7
    Join Date
    Aug 2007
    Location
    Northern California
    Posts
    193

    Default

    Quote Originally Posted by engrx2 View Post
    Thanks everyone, I measured the voltage on the pot wiper and it is linear from zero to the max setting. But when I plotted the current output as a function of the pot position, its like the first 1/3 turn does nothing. Also, the relay, CR1, doesn't actuate at all until I get past the 1/3 turn.
    Voltage tests won't tell much if the potentiometer is still in the circuit. What is important is the resistance of the pot. when disconnected from the circuit.

    If the first third of the pot's movement does little or nothing, then it is by definition non-linear, i.e., Audio taper. This is further shown by your statement that the relay doesn't move until past the first 1/3 turn. This proves that the resistance is greater in that position than a similar linear pot. would be.

    I'm betting with those who say that the wrong pot. was installed. I would remove the pot and test it for resistance and, if non-linear, replace it with a liner pot of the correct wattage.
    Miller Syncrowave 200
    Milermatic 252
    Lincoln AC/DC "Tombstone"

  8. #8
    Join Date
    Aug 2013
    Posts
    12

    Default

    Well I tried it with the Miller foot pedal and I get the same effect: No current for the first 1/3rd of the pedal, then the current picks up gradually to full current at the bottom of the pedal. So I think something in PC1 is flaky. And I cannot adjust it out with the on board trip pots.

  9. #9
    Join Date
    Oct 2004
    Location
    Edmonton, Alberta
    Posts
    7,832

    Default

    Quote Originally Posted by engrx2 View Post
    Well I tried it with the Miller foot pedal and I get the same effect: No current for the first 1/3rd of the pedal, then the current picks up gradually to full current at the bottom of the pedal. So I think something in PC1 is flaky. And I cannot adjust it out with the on board trip pots.
    Well if the local control pot is not correct then your remote will be wonky as well, cause they work in tandem. Geez change the thing. Looking for a 1 K ohm 2 watt pot. Any electronics store will have it. Might cost 6 bucks

  10. #10
    Join Date
    Oct 2004
    Location
    Edmonton, Alberta
    Posts
    7,832

    Default

    Either the wrong type of potentiometer or the wrong resistance.

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