Refurbishing an old Miller Thunderbolt 225 AC
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  1. #1

    Refurbishing an old Miller Thunderbolt 225 AC

    Not sure where to put this, so I just put it here. Feel free to move if I'm in the wrong place.

    I'm as green to welding as they come. For years I've wanted to learn. I live on and run a small farm. I have dozens of uses for one. I broke a bush hog mower at the mount Saturday and long story short, I've been given an old (very old) Miller Thunderbolt 225 AC style HD-6. According to the Miller website, it was built in 1973 or 74. It has been sitting unused since 1993. I'm told it worked when it was put up.

    My shop is wired with an RV plug and I'm building a extension / adapter cord for a 6-50 receptacle tomorrow night. Before I plug this thing in, I wanted to run it by y'all.

    I downloaded the manual from Miller's website and followed the maintenance instructions to grease the shunt block. I oiled the fan bearings. The fan turned fine and had no wobble to indicate a bad bearing. I cleaned it all up inside and blew out all dust. Checked the wiring for obvious shorts. Cleaned connections. Everything looked to be in running order to my untrained eyes.

    Anything else y'all can think of that I need to do prior to trying it out? Do I have any chance of this 38 year old welder running? Any other tips?

    I intend to clean it up more and repaint if it works. Here's a pic.


    Thanks in advance for any help you can offer.

  2. #2
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    Re: Refurbishing an old Miller Thunderbolt 225 AC

    Those machines are darn near bullet proof. Your's looks like it's practically new from the pict. I've seen ones all rusted and beat up that still welded fine. My guess it it will run with no problems with what you have done.

    The only thing I would do is look over the leads well to make sure they are in good shape and don't have any bad spots from dry rot in the insulation. If they are not all cracked and crumbling, you should be good to go.

    I'd suggest starting out with 7014 in 3/32". 7014 is a drag rod. All you have to do is keep the flux in contact with the steel and drag it along at about a 30 deg angle pointed back at where you have welded. You will find the suggested amp settings on the package. Start in the middle of the suggested range.
    Last edited by DSW; 08-15-2011 at 08:46 PM.
    .



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  3. #3

    Re: Refurbishing an old Miller Thunderbolt 225 AC

    It's definitely not practically new. Maybe it's the distance in the picture or possibly that pretty tractor in the back ground is making it look better It's not in bad shape, though. Definitely doesn't look 38 years old. Has some surface rust on the cover and it was filthy inside. A couple of dirt dobber nests, but it didn't appear to have any mice chewing on the wires. The leads look fine to me. No noticable cracks and seem very pliable.

    We'll see tomorrow. Thanks for the reassurance.
    Last edited by stravis; 08-15-2011 at 08:59 PM.

  4. #4
    Join Date
    Jan 2009
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    Re: Refurbishing an old Miller Thunderbolt 225 AC

    Run the amp adjustment end to end. Listen for squeaking and feel for resistance when turning the handle.
    These welders take objection to being stored in an unheated environment so that the frost and dew can form on it. Corrodes the shunt and makes it harder and harder to move. Eventually results in a stripped adjustment screw.

    I have to take exception to the description of bulletproof. This amp adjustment design is a problem looking for an opportune time to strike. You want bulletproof, get a Lincoln 225-AC
    Gordie -- "I believe you understand what you think I said, but I'm not sure you realize that what you heard is not what I meant."

  5. #5

    Re: Refurbishing an old Miller Thunderbolt 225 AC

    The amp adjustment moves fine, although there is definitely resistance but no squeaking at all. I've never turned one before so I don't know what's normal, though. When I removed the cover tonight I greased the screw and it looked brand new. Not stripped at all. The block, however had some corrosion. Not too bad, but there was some. How big of a problem is that and what should/can I do about it (other than grease it as I did tonight)?

    Thanks for the help.

  6. #6
    Join Date
    Jan 2011
    Location
    South East Michigan
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    322

    Re: Refurbishing an old Miller Thunderbolt 225 AC

    Hey one last thing if y'all don't mind me chiming in. I actually have a little exp. with this model and one of the things that had me stumped for a while was a loose nut on the back of one of the output terminals on the panel.

    One of them (I think its the AC output on the left as you look at the panel) acts as both a connection to where you plug your lead into and an internal jumper connection between the two secondary transformer side commons. Kind of hard to explain in txt. but essentially, if that nut comes loose (even a little) it will wreak havoc inside the welder and/or cause problems with the output.

    Its unlikely that this is the case with your almost new looking buzzbox but it can happen and since you've already checked everything else, why not right?

    Have fun!

    Eric

  7. #7

    Re: Refurbishing an old Miller Thunderbolt 225 AC

    I'll check it. Thanks for the tip.

  8. #8
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    Re: Refurbishing an old Miller Thunderbolt 225 AC

    Quote Originally Posted by stravis View Post
    The amp adjustment moves fine, although there is definitely resistance but no squeaking at all. I've never turned one before so I don't know what's normal, though. When I removed the cover tonight I greased the screw and it looked brand new. Not stripped at all. The block, however had some corrosion. Not too bad, but there was some. How big of a problem is that and what should/can I do about it (other than grease it as I did tonight)?

    Thanks for the help.
    According to the manual, grease is what is needed to keep the shunt sliding freely. Greasing the screw is not what you have to do. Grease the shunt (what you called the block). There are 4 points to apply grease to.

    I like to keep a rag on top of my welder. Keeps grinding dust out of the adjustment screw.
    Gordie -- "I believe you understand what you think I said, but I'm not sure you realize that what you heard is not what I meant."

  9. #9

    Re: Refurbishing an old Miller Thunderbolt 225 AC

    Quote Originally Posted by Nitesky View Post
    According to the manual, grease is what is needed to keep the shunt sliding freely. Greasing the screw is not what you have to do. Grease the shunt (what you called the block). There are 4 points to apply grease to.

    I like to keep a rag on top of my welder. Keeps grinding dust out of the adjustment screw.
    I did grease both outside and the inside of the shunt block as it's called in the manual. Four points in total. The diagram in the manual looked like it called for you to grease the screw as well, so I did.

    So the light corrosion on the shunt shouldn't be a problem, then? As long as I applied grease as called for?

  10. #10
    Join Date
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    Re: Refurbishing an old Miller Thunderbolt 225 AC

    Sounds like the time to plug it in and flip the switch has come. Enjoy the Thunderbolt in good health.
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  11. #11
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    Re: Refurbishing an old Miller Thunderbolt 225 AC

    Quote Originally Posted by stravis View Post
    I did grease both outside and the inside of the shunt block as it's called in the manual. Four points in total. The diagram in the manual looked like it called for you to grease the screw as well, so I did.

    So the light corrosion on the shunt shouldn't be a problem, then? As long as I applied grease as called for?
    If the corrosion provides extra resistance when you turn the crank to adjust it is time to take things apart and clean. If not then no problem.

    The problem cropped up when I had to adjust beyond my normal comfort zone. Now, I will take and run the adjustment from min to max once before every use of the machine.

    When I had the shunt out to replace the lead screw I took my Dremel and with a tiny wire wheel, cleaned the shunt. All problems went away at this point. Am not a fan of this design by any means.
    Gordie -- "I believe you understand what you think I said, but I'm not sure you realize that what you heard is not what I meant."

  12. #12

    Re: Refurbishing an old Miller Thunderbolt 225 AC

    It worked perfectly fine. I had an issue last night with the breaker tripping and before I could figure it out, the gnats ran me out of my shop. Tonight I found that I had the uncoated ground touching one of the hot lugs in a plug. Fixed that and all was well.

    I appreciate the tips and look forward to learning more from y'all.

  13. #13
    Join Date
    Jan 2006
    Location
    Snellville GA
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    215

    Re: Refurbishing an old Miller Thunderbolt 225 AC

    Thanks to everyone for all the information. I just bought a 1990 vintage Thunderbolt AC/DC last night and will start reconditioning in the near future. It works OK looks but is sad looking machine.
    I'll take some pictures and start a thread when I get into it.

  14. #14
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    Re: Refurbishing an old Miller Thunderbolt 225 AC

    I've had 2-3 of these. Now I have the newer Thunderbolt.
    I agree with DSW, these are pretty rugged machines. Clean them up, follow the manual with oiling the shunt, etc. I have found the surface rust is not much of a problem, just clean it up, wax it and it will look like new. Rustoleum Industrial Blue paint is a close enough match if you're not a perfectionist. Afterall, it's just some wire and copper moving up and down. No circuit boards or electronics to foul.
    Clean it up, use common sense in checking the electrical connections, and let 'er rip! I'm sure you will be pleased and can always get your money back.
    Burt
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