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  1. #1
    Join Date
    Jun 2010
    Posts
    3

    Default Miller CP 300 Problem

    Hello, I have been working on a cp300 that I bought to use in my shop, When I got the welder, the control relay cr1 was bad and it would'nt do anything but run the fan. I replaced cr1 and the welder would weld, but after a short period (1/3 of a 1/8" 7018 ) it will just lose the arc. in a moment it will weld again, well arc again anyway, but it is an erratic arc, acting cold one second and hot the next. When I got the welder the jumper links were set to 480v I set them to 230 and have rechecked their position to make sure they were set correctly. The power in the shop measures 240 leg to leg, 120 to ground on two phases and 235 or so to ground on one phase. I have the wild leg connected to L2. I tried jumping the thermostat to make sure it was not opening, and it made no difference. I checked the contacts and while they didn't look new they didn't look bad. I have cleaned the cable connections. I put a meter from the positive to work legs and the voltage is erratic. The surface of the coils where the brushes meet them look ok and are not pitted. If anyone has been there done this I would appreiacte any help youi could offer. I would like to fix this old welder and also use it with a s-22a feeder. thanks -dave

  2. #2
    Join Date
    May 2010
    Location
    Central CA
    Posts
    781

    Default CV only

    Correct me if I'm wrong, but isn't CP-300 a CV only machine.
    Millermatic 252 w/30A
    Big Blue Air Pak
    Ellis 3000 Band Saw
    Trailblazer 302 Air Pak w/ Wireless Remote
    8-RC
    Dynasty 200 DX
    XMT 350 MPa w/S-74 MPa Plus
    Millermatic 211
    Passport Plus
    Spectrum 625 X-TREME
    Lincoln SA-200 Blue Tint Red Face '63
    2-Lincoln SA-200 Red Face '68
    SA-200 Black Face '59
    SA-200 Green Lite '84
    SA-200 Green Lite '80
    SA-200 Red Face '69
    SA-200 Red Face '66
    SA-200 Green Lite '81
    '70 Black Face Round Barrel

  3. #3
    Join Date
    Jun 2010
    Posts
    3

    Default

    Bob I'm new to working on a welder , I couldn't correct you , The cp 300 I have is a constant voltage machine with the 14 pin connection I'm sure i've just shown my ignorance again but can you elaborate for a novice..

  4. #4
    Join Date
    May 2010
    Location
    Central CA
    Posts
    781

    Default 3 Phase

    Both of my CPs are 3 phase only. If you have 3 phase hook up the 22A and start welding with wire. On those machines it does not matter how you put the legs.
    Just make sure you have 3 hot legs.
    Good Luck
    Bob
    Millermatic 252 w/30A
    Big Blue Air Pak
    Ellis 3000 Band Saw
    Trailblazer 302 Air Pak w/ Wireless Remote
    8-RC
    Dynasty 200 DX
    XMT 350 MPa w/S-74 MPa Plus
    Millermatic 211
    Passport Plus
    Spectrum 625 X-TREME
    Lincoln SA-200 Blue Tint Red Face '63
    2-Lincoln SA-200 Red Face '68
    SA-200 Black Face '59
    SA-200 Green Lite '84
    SA-200 Green Lite '80
    SA-200 Red Face '69
    SA-200 Red Face '66
    SA-200 Green Lite '81
    '70 Black Face Round Barrel

  5. #5
    Join Date
    Aug 2008
    Location
    Orange, TX
    Posts
    1,200

    Default

    Quote Originally Posted by Bob Miller View Post
    Correct me if I'm wrong, but isn't CP-300 a CV only machine.
    Sure is.

    Dave,
    As Bob was implying, the CP300 is a Constant Voltage (CV) power supply designed and meant for MIG welding (that S-22A wire feeder) and not stick or TIG.

    That said, double check those brushes to make sure they're all free in their holders. They have a habit of sticking due to rusty holders and/or dust build-up and loosing contact with the transformer windings.

    If I understood you correctly you already checked the mechanical contactor to make sure its contacts were clean which would be my next spot to look.

    And then on to the diodes in the weld output rectifier but one or more failed diodes usually means a short (tripping breakers) or low/no output rather than fluctuating but anything is possible.

    What is the unit SN?
    MM200 w/spot controller and Spoolmatic 1
    Syncrowave 180 SD
    Bobcat 225G Plus LPG/NG w/14-pin*
    *Homemade Suitcase Wire Feeder
    *HF-251D-1
    *WC-1S & Spoolmatic 1
    PakMaster 100XL
    Marquette "Star Jet" 21-110

  6. #6
    Join Date
    Aug 2008
    Location
    Orange, TX
    Posts
    1,200

    Default

    I'm with Bob. Hook it up to the S-22A (correct process device) and go from there.
    MM200 w/spot controller and Spoolmatic 1
    Syncrowave 180 SD
    Bobcat 225G Plus LPG/NG w/14-pin*
    *Homemade Suitcase Wire Feeder
    *HF-251D-1
    *WC-1S & Spoolmatic 1
    PakMaster 100XL
    Marquette "Star Jet" 21-110

  7. #7
    Join Date
    May 2010
    Location
    Central CA
    Posts
    781

    Default

    For 7018 you need a CC (constant current). Your CP (constant potential) is constant voltage (CV) for wire only. And they only run on 3 phase power.
    Bob
    Last edited by Bob Miller; 06-06-2010 at 08:23 AM.
    Millermatic 252 w/30A
    Big Blue Air Pak
    Ellis 3000 Band Saw
    Trailblazer 302 Air Pak w/ Wireless Remote
    8-RC
    Dynasty 200 DX
    XMT 350 MPa w/S-74 MPa Plus
    Millermatic 211
    Passport Plus
    Spectrum 625 X-TREME
    Lincoln SA-200 Blue Tint Red Face '63
    2-Lincoln SA-200 Red Face '68
    SA-200 Black Face '59
    SA-200 Green Lite '84
    SA-200 Green Lite '80
    SA-200 Red Face '69
    SA-200 Red Face '66
    SA-200 Green Lite '81
    '70 Black Face Round Barrel

  8. #8
    Join Date
    Jun 2010
    Posts
    3

    Default

    Thanks, Its nice to confirm that I'm an idiot. as have been trying to stick weld off this machine, the serial number is KF765659 Thanks for the education I will hook up the wire feeder and see how it goes. with my hat over my face, I say thanks again!

  9. #9
    Join Date
    Aug 2008
    Location
    Orange, TX
    Posts
    1,200

    Default

    Don't sweat it Dave. Just part of the learning curve.
    MM200 w/spot controller and Spoolmatic 1
    Syncrowave 180 SD
    Bobcat 225G Plus LPG/NG w/14-pin*
    *Homemade Suitcase Wire Feeder
    *HF-251D-1
    *WC-1S & Spoolmatic 1
    PakMaster 100XL
    Marquette "Star Jet" 21-110

  10. #10
    Join Date
    May 2010
    Location
    Central CA
    Posts
    781

    Default

    Dave,

    Don't leave us hanging, tell us how it goes. We all want to hear a success story.
    Bob
    Millermatic 252 w/30A
    Big Blue Air Pak
    Ellis 3000 Band Saw
    Trailblazer 302 Air Pak w/ Wireless Remote
    8-RC
    Dynasty 200 DX
    XMT 350 MPa w/S-74 MPa Plus
    Millermatic 211
    Passport Plus
    Spectrum 625 X-TREME
    Lincoln SA-200 Blue Tint Red Face '63
    2-Lincoln SA-200 Red Face '68
    SA-200 Black Face '59
    SA-200 Green Lite '84
    SA-200 Green Lite '80
    SA-200 Red Face '69
    SA-200 Red Face '66
    SA-200 Green Lite '81
    '70 Black Face Round Barrel

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