CP-200 converted need help
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  1. #1
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    Default CP-200 converted need help

    Long time reader not much of a poster. I converted my machine a while back and been troubled ever since. I picked it up not knowing the state of welder to begin with.

    I did the conversion step for step being careful with wires because its one of the first years they was built.

    It's spits n sputters some. Melts wire but does not stick to metal.

    I've cleaned the brushes and stoned the contactor suraces.

    Whats next?

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    Quote Originally Posted by AlabamaGMC View Post
    I did the conversion step for step being careful with wires because its one of the first years they was built.

    It's spits n sputters some. Melts wire but does not stick to metal.
    Do you mean conversion to/from 3 phase? A Miller CP-200?

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    Yes. It's a Miller CP-200. I did the haas-kamp conversion to it.

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    One of the things that the CP series suffered from, was brittle wires coming from the primary coils to the back of the terminal strip... they'll crack right at the terminal, and seem 'very much' like they're fine, but if you investigate further, you'll find cracked wires that are only making partial contact. I'm certain that this circumstance took many a CP out of shop operation and into back corners and scrap piles.

    Another thing I've found, is that since many were pulled out and rolled aside, the variable-tapping on the control side makes much less-than-adequate contact due to elemental corrosion and crud on the contact points. I found that cranking the output control to one extreme, and scrubbing all the contacts to shiny-clean with a Scotchbrite pad (actually used a 'soft' disc in an air-tool) to do it... then cranked the output to other extreme and repeated for the area covered by the brushes. Then I rinsed out the brush area with aerosol solvent (contact cleaner is preferred) then a shot from the air compressor, and it wakes 'em right up.

    Make certain that your cable connections are good... at the terminals, and cables throughout. I test mine with a crowbar- put a three-four foot long chunk of steel angle or rebar 'tween the ground and hot cables, then activate the supply at lowest setting, and look at the output meters... should indicate appropriate voltage and current, and after it's grunted for a few seconds, deactivate, then feel all the cables and connections- any signs of warmth indicate a poor conductor or connection.

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    Thanks. I'll test the crowbar. I cleaned up the brushes and the winding surfaces first off when I did the conversion. Is there any way to check for the broke wires coming out of the windings with a meter? Continuity? It's old for sure. Your saying with crowbar in a dead shit the leads shouldn't warm up? Thanks Dave for responding.

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    Might be a dumb question. Does the voltage and a amp hand go hand n hand on readings?

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    As long as resistance across the bar and leads stays constant, when you increase voltage, the current output should increase. With a dead short, the leads WILL warm, but the warmest part will be the points of greatest resistance.

    Don't do it for more than a few seconds at a time- connect the leads, make sure everything's tight, then trigger the power contactor for about four seconds, then release. Most likely, you'll see the ammeter go to full scale. After four seconds, release the contactor, shut it down, and feel the connections and leads.

    Best way to check for broken wires, is to remove the bolts holding the red terminal strip, pull it out just enough to get in there with hands, and push on each one with fingers. If one is cracked, you'll see it open up when you press on it.

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    I did the crowbar test.

    1st test..... Volt meter read what the dial said it was. Ammeter didn't move.

    Tighted grounding clamp nuts on machine.

    2nd test.... Volt maybe went to 5 volts. Ammeter pegged out.

    Felt of wires and connections. Contactor wires was warm.

    Triggered it again and watched contactor and one legged was sparking good. No changes made.

    3rd test.... Cranked up to 36 volts on dial. Squeezed trigger. Volts might have gotten past 5 but not to 10. Same with ammeter as before.

    Conclusion is to get new contactor and repeat test.

    Dave....your thoughts?

    256-302-2825 if you'd like to call.

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    Quote Originally Posted by AlabamaGMC View Post
    Yes. It's a Miller CP-200. I did the haas-kamp conversion to it.
    You will get better help on the Miller discussion forum.

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    Sorry, I was on assignment on the Arizona/Mexico border for a while, and missed this.

    Quote Originally Posted by AlabamaGMC View Post
    I did the crowbar test.

    1st test..... Volt meter read what the dial said it was. Ammeter didn't move.

    Tighted grounding clamp nuts on machine.

    2nd test.... Volt maybe went to 5 volts. Ammeter pegged out.
    I think you probably found your answer right there- first one showed full suggested voltage and no current, and after tightening the nuts, your voltage dropped to extreme low (crowbar being practically zero resistance) and infinity on current. Did you try welding with it afterwards?

    Quote Originally Posted by AlabamaGMC View Post
    Felt of wires and connections. Contactor wires was warm.

    Triggered it again and watched contactor and one legged was sparking good. No changes made.

    3rd test.... Cranked up to 36 volts on dial. Squeezed trigger. Volts might have gotten past 5 but not to 10. Same with ammeter as before.
    Which is to be expected- you've increased voltage output across a practically-zero-resistance shunt, which increases current dramatically through the shunt, but you're already off the meter, and with zero-resistance shunt, the output voltage will only indicate a little higher. At this point, you're probably deflecting all the compasses within 10 miles' radius...


    Quote Originally Posted by AlabamaGMC View Post
    Conclusion is to get new contactor and repeat test.

    Dave....your thoughts?
    I've had bad contactors, but I don't think that yours is... it appears that the nut you tightened had a marginal connection, so hook up the gun and try welding with it again.

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    Quote Originally Posted by rons View Post
    You will get better help on the Miller discussion forum.
    I'm sure he probably would, once they referred him to the guy that actually developed the conversion.

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    Thanks Dave! I enjoyed the phone call. I replaced the contactor with a known good one. No change in out come.

    I switched the ground and gun around on polarity as Dave recommend over the phone.

    Welds like it should now. Beautiful welds.

    No need to be snippy rons.

    Big thumbs up to the Haas-Kamp conversion.

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    what a stand up guy!


    Glad to see another successful cp converted

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    Quote Originally Posted by DaveKamp View Post
    I'm sure he probably would, once they referred him to the guy that actually developed the conversion.
    Dave, good work.

  15. Likes DaveKamp liked this post
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    Thanks, Ron- I appreciate that. The whole reason for this conversion, is so that guys who'd like an industrial-grade machine, but have to live on a hobby budget, can have both. The only down-side, is that some guys fear working with electricity (understandable) and these machines come to them with an unknown past and cannot be tested prior to conversion, so they often need a little ancillary TLC.

    Fortunately, the CP is easy to work on, well built, simple as a hammer, and in Miller's case, very well documented... I tip my hat to Blue for that... not only on this, but their other industrials of long. I'll grant Lincoln applause, as they do very well posting their manuals and diagrams online.

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    could you just quit your job and sit by the computer Dave?

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    Quote Originally Posted by DaveKamp View Post
    Thanks, Ron- I appreciate that. The whole reason for this conversion, is so that guys who'd like an industrial-grade machine, but have to live on a hobby budget, can have both. The only down-side, is that some guys fear working with electricity (understandable) and these machines come to them with an unknown past and cannot be tested prior to conversion, so they often need a little ancillary TLC.

    Fortunately, the CP is easy to work on, well built, simple as a hammer, and in Miller's case, very well documented... I tip my hat to Blue for that... not only on this, but their other industrials of long. I'll grant Lincoln applause, as they do very well posting their manuals and diagrams online.
    When I looked at the last pages of your document I was reminded of the time I contacted
    Repco about replacing contact points for old out of date parts. I was convinced they could
    replace worn points from their website. I contacted them but got no reply. During the years
    after 9/11 I noticed that companies would take whatever business came their way. When times
    are better it is different. Like the electrical supply house I used to go to. Before there
    was no minimum order. Now there is a $150 minimum order with a 40% charge on returns.

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    Yeah, that happens. I'm sure there's a myriad of factors that make suppliers change their pricing and policies. For electrical contacts, there's a whole lotta dependancy on the materials markets. Contact platings like silver, gold, etc., can be incredibly expensive to produce at some times, but much less expensive at others. When there's a store of new old stock available, they're often found to be a liability at some times (like when the bean counters look at slow moving inventory and the rolled-up investment was high) and an asset at other times (like when there's high demand and investment costs were low). This kind of stuff seems to be most visible when companies are bought and sold, or when their stock prices are unstable. When subcontract suppliers are involved, or even dissolved, quantities of parts come available at extremely low prices, so they appear miraculously at a former customer's doorstep, which makes it even more confusing.

    The marching-on of technology continues... which is exactly how output contactors got superceded by SCRs in the output stack. They do work very well, but SCRs are a serious PITA to open up and clean...

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    Quote Originally Posted by wippin' boy View Post
    could you just quit your job and sit by the computer Dave?

    What job? :-D

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    Quote Originally Posted by DaveKamp View Post
    Yeah, that happens. ...
    The electrical supply outlets (walk-ins) near to me are getting out of sight (price wise). A little contactor with overload block
    that has a foot print smaller than the size of you palm is > $350. I witnessed a man who tried to return a unused contact block which
    he never used and they said the restock fee would be $140. All of this just because the coil voltage was 230 not 115. He was so pissed
    he ended up keeping it. Outside the building I started talking with him and he invited me to his welding business to help trouble-shoot a problem.


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