Miller bobcat 225g Plus Help!!!
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  1. #1

    Miller bobcat 225g Plus Help!!!

    Okay guys i just picked up a Miller bobcat 225G Plus yesterday for 300 bucks with an Onan motor from my local welding supply house. Was told that it ran but that the generator was bad. Got it home and changed out some rotten fuel hoses that were leaking and put fuel in it and got it to fire up and runs like a top. However i have no output power at the 110 receptacles. did some digging on here and i found that The F1 and F2 fuses were completely missing from the machine, so i put two new fuses in. and fired it up with still no power to the 110 outlets and the F1 blown, F2 still intact. i need some help on where to go from here. Thanks Croft

  2. #2
    Join Date
    May 2008
    Location
    Orange, TX
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    Re: Miller bobcat 225g Plus Help!!!

    I would start by checking field bridge rectifier SR2. Review the unit circuit diagram and parts breakdown to identify it if you're not sure what/where it is.

    You should look for one or more shorted legs (continuity in both directions of two adjacent terminals).



    If the welding supply place knew the generator was bad did they not tell you what was defective?
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  3. #3
    Join Date
    May 2010
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    ct.
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    Re: Miller bobcat 225g Plus Help!!!

    Edit- never mind ,i was going to say check field rectifiers
    Duane beat me to it
    Last edited by jpump5; 08-05-2018 at 07:14 PM.
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  4. #4

    Re: Miller bobcat 225g Plus Help!!!

    it was a backdoor deal in which my buddy knew where the welder was and that it ran and was told the generator was bad. i jumped on it because the motor ran good. As far as the field bridge rectifiers, what exactly am i looking for? sorry for my ignorance I'm no electrician but i do know my way around a wiring diagram.

  5. #5
    Join Date
    May 2008
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    Re: Miller bobcat 225g Plus Help!!!

    There should be a circuit diagram on the inside of one of the side panels. Look for SR2 in the diagram and then check the Parts List in the owners manual for its location behind the control panel.

    If you don't have the manual you can download it here . . .
    https://www.millerwelds.com/support/manuals-and-parts

    . . . but SR2 is located near the fuse F1 that you replaced.

    Name:  Bobcat 225G Plus Exciter Diode 001.jpg
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    MM200 w/Spoolmatic 1
    Syncrowave 180SD
    Bobcat 225G Plus - LP/NG
    MUTT Suitcase Wirefeeder
    WC-1S/Spoolmatic 1
    HF-251D-1
    PakMaster 100XL
    '68 Red Face Code #6633 project
    Star Jet 21-110

    Save Second Base!

  6. #6

    Re: Miller bobcat 225g Plus Help!!!

    okay perfect i have located that. now from there how do i test to see if it is bad or not? do i need to go ahead and pull it out to test it or can i do it in the machine? also how do i go about cleaning the inside of this machine its super dusty and all of the wiring is covered in dust. i would assume water is not the go to cleaner here.

  7. #7

    Re: Miller bobcat 225g Plus Help!!!

    ok so i got a new SR2 bridge rectifier. replaced the blown F1 fuse cranked it up and blew the F1 again.. no clue where to go from here..HELP!!

  8. #8

    Re: Miller bobcat 225g Plus Help!!!

    the slip rings are really dirty, could that cause the F1 fuse to blow?

  9. #9
    Join Date
    May 2010
    Location
    ct.
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    947

    Re: Miller bobcat 225g Plus Help!!!

    I don’t know that dirty slip rings would cause
    that,but it would be worth trying.
    I would measure resistance of rotating winding,
    looking for a short in the winding.
    Hopefully someone here knows the proper resistance.
    I’d consider a resistance less than 8-10 ohms
    to be suspect.
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  10. #10
    Join Date
    Jul 2012
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    585

    Re: Miller bobcat 225g Plus Help!!!

    Had this happen to a Hobart champion 16 which is pretty much set up like the Bobcat. Checked the bridge rectifier and it tested bad. Ordered two from Allied Electronics for under $5.00 each, replaced fuse and installed bridge rectifier and fuse blew and toasted bridge rectifier. More testing and found bad capacitor. Then replaced fuse,bridge rectifier and cap, then it worked.

    The reason the machine broke was using Air arc, guess exceeded the duty cycle but has been running great since repair.
    Last edited by guajilloweld03; 08-08-2018 at 07:26 PM.

  11. #11

    Re: Miller bobcat 225g Plus Help!!!

    may need help with that. I'm very green when it comes to electricity and wiring. i can read a wiring diagram but thats about the extent of it. i don't have a volt meter or anything of that nature.

  12. #12
    Join Date
    Jul 2012
    Posts
    585

    Re: Miller bobcat 225g Plus Help!!!

    Know how you feel about trouble shooting as my reading comprehension is very low/slow, if there are no pictures have a tough time understanding.

    This manual has helped me figure things out since do not do this type of troubleshooting often enough.

    https://www.westerbeke.com/troublesh...ing_manual.pdf

    For a meter just get one at Harbor freight

    https://www.harborfreight.com/11-fun...ity-61593.html

    Then find a youtube video on how to use a meter.

    Read your post again, my machine was generating power at outlets but was not welding. You will have to follow a trouble shooting guide and test components as needed.
    Last edited by guajilloweld03; 08-08-2018 at 11:16 PM.

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