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Thread: Miller Bobcat 250NT help please

  1. #1
    Join Date
    Jun 2022
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    Miller Bobcat 250NT help please

    Hey guys I picked up a 250 NT, after getting it home its quite the mess but the price was right, I was told it ran and welded years ago when put into storage then when started years later it would not put out power. I found F6 and F2 both to be bad and blown. I popped the flywheel and found a destroyed stator and no magnets left in the flywheel, so before I buy any parts I would like to make sure the welding/generation portion of the machine is functional. On that end I found F2 to be open and the CAP to be shorted, the bridge and other diode are fine but I will change them anyway, the ohms across the slip rings is about 3ish, this is an 8k generator model. What else should I look for before I start ordering stuff?? I appreciate any and all help


    Thanks Mike

  2. #2
    Join Date
    Jun 2012
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    Big Lake/Monticello MN
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    Re: Miller Bobcat 250NT help please

    I would probably buy another 250nt and use this one for random parts as needed.
    Do you have an approximate price for parts yet?
    Dave J.

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

    Syncro 350
    Invertec v250-s
    Thermal Arc 161 and 300
    MM210
    Dialarc
    Tried being normal once, didn't take....I think it was a Tuesday.

  3. #3
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    Jun 2022
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    Re: Miller Bobcat 250NT help please

    Im looking between 4-500, I have 350 into it so if its 5 in parts all said n done ill be under 1000.

  4. #4
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    Jun 2022
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    Re: Miller Bobcat 250NT help please

    making some headway on this machine, had it running today engine sounds good, will not run without batt connected, i just put a stator and magnets in it, the origs were destroyed, batt shows 12v when starting n near that at idle if you rev it up voltage goes down , i am guessing the regulator is bad,correct me if I am wrong , Thanks Guys ....if batt is disconnected it stalls.

  5. #5
    Join Date
    Dec 2008
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    Lockhart,Tx (BBQ capitol of the world)
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    Re: Miller Bobcat 250NT help please

    Sounds like the voltage regulator is bad.

    By the way you should never disconnect the battery on a running engine!
    It will probably wreck the regulator and possibly the alternator also!

  6. #6
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    Jun 2022
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    Re: Miller Bobcat 250NT help please

    Few questions guys,
    My machine has a 950uf 75vdc cap in it which is shorted I ordered a replacement but the serv manual says its a 100uf 75vdc, was there an upgrade or bulletin out on this unit at some point beefing up the cap ?? also the F1 fuse was blown as a result of that, are these ceramic fuses any different than any other 25A fast acting fuse ??

    Thanks

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