New to me DOA Millermatic 250 Miller Mig

Hello,
I haven't posted in a while, but thought I'd start a thread related to my latest welder purchase. This is my first (let the games begin) Mig welder. While I probably should have bought a new, or lightly used smaller welder, like a Hobart handler, or Lincoln Weldpak (nothing against Miller, just don't know what their cheapest migs are called.....if they even make any "cheap" ones).

But I happened upon a surplus auction for this Millermatic 250 in non working condition, and one the auction. All in, bid price, buyer's premium, and taxes....$59!

It came out of a vocational technical high school (possibly abused?).

It's missing the gun/cable assembly (M25??), but I can get one off Ebay when the time is right, and I'm not buying one until I know just what I'm in for repair wise.

More bad news.....I insist on trying to repair this myself:eek:

I have an electronics background, so I know what a rectifier is, and understand basic electricity, but I'm a far cry from a welder repair professional.

But I'm hoping the friendlier amongst you might offer some helpful advice, and I do not mean "scrap it". or "bring it to a professional". Not that the latter isn't good advice, it's that I'm too stubborn to take it.

I have started a youtube series chronicling this project. Here is part one with an initial first look:

https://youtu.be/PpfpThu4G6U

I'll add some photos later for anybody that wants to see the welder and not watch a video.

Looking forward to learning from those in the know.

Steve.

Here is a link to the owner's manual for that machine https://www.millerwelds.com/files/ow...O1308M_MIL.pdf

Seems like that is built very similar to a syncrowave. It has a main circuit board (PC1 184316) that controls the SCRs, and they regulate the output. Assuming it is not something simple, it is probably a fired circuit board or a problem with the SCR/thyristor array. At least that is what usually seems to cause trouble on the syncrowaves. If the circuit board is fried a new one from airgas is ~$550. You may be able to fix it yourself, or send it out for repair for less money.

what are the websites you search to find these surplus welders? I am always up for bargain.

Contact Miller. They should be able to get you a copy of the repair manual, or at least walk you thru the trouble shooting portions.

Get the manual and start checking with a dvom. Gotta start somewhere.
Are you sure it doesn't work?
I've bought several in " non working" condition and they have been fine. Most out of schools here are missing leads and such and most are listed as non working so it makes the sale final. I picked up a dialarc they said wasn't working and it's a sweet running welder.
Does it power up at all or dead with no response?

The owners manual I posted has the schematic. You will want to get the tech manual if you want to try any serious repairs yourself.

PM me your email address. I'll send you a copy of the tech manual.

You may be in for an expensive and difficult repair. It really just depends what's wrong with it. A service tech in Austraila walked a member thru a difficult repair on one of these a few years ago. I'll see if I can find the thread. I work on welders, but not those and my knowledge base is somewhat limited.

You're gonna want to start with the sequence of operation flow chart in the manual. It will give you a basic idea how power flows thru the machine. The troubleshooting sections in these manuals are usually vague at best, youll probably want to refer to the testing schematic in the tech manual which will tell you what to test and what the values should be. There are also detailed test value charts for the board too, which will tell you what you want to look for and where to place your meter probes to read the values. There isnt a pre power checklist for this unit unfortunately, that mostly applies to inverters.

ccawgc here is a very sharp tech and may be able to offer some assistance. He's usually pretty busy but has never turned anyone down that's asked for help here. You may wanna PM him and see if he has some time to offer some advice. He's a great guy and has helped me more than I can even remember.

If you do not have a good meter, GET ONE. A cheap junk harbor freight meter is as good as a magic 8 ball and will be a waste of time to try and use. I assume you already have one, but a decent unit can be purchased at any big box store or place that sells tools. $60 is more than enough to get a good unit with ohms, capacitance and diode reading.

PM me that email.

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Originally Posted by Louie1961

what are the websites you search to find these surplus welders? I am always up for bargain.

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I won this auction on publicsurplus.com unfortunately I rarely get good deals on there. Im on the Massachusetts Connecticut border and most of the close items are over an hour drive into Connecticut and the prices run high. I got lucky on this welder because a Massachusetts school decided to dump 3 welders. One auction was for a shopmaster 300 with a coolmate cooler in working condition. I think that brought over $600. The other 2 were millermatics. A working 250x and my 250. Maybe you'll have better luck in your area.

Steve.

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Originally Posted by Michael ray

Get the manual and start checking with a dvom. Gotta start somewhere.
Are you sure it doesn't work?
I've bought several in " non working" condition and they have been fine. Most out of schools here are missing leads and such and most are listed as non working so it makes the sale final. I picked up a dialarc they said wasn't working and it's a sweet running welder.
Does it power up at all or dead with no response?

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I think you hit the nail on the head. I did some tests tonite and jumping the pins on the trigger connector opened the gas solenoid, started the feed motor, and produced a dc voltage output! I'm buying a gun and a couple small parts missing on the spool tensioner.

sweet.

Quote:

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Originally Posted by stevewatr

I think you hit the nail on the head. I did some tests tonite and jumping the pins on the trigger connector opened the gas solenoid, started the feed motor, and produced a dc voltage output! I'm buying a gun and a couple small parts missing on the spool tensioner.

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If all you have to do is buy a new gun, that's cuase for a celebration beer!

Awesome buy

Thanks for all the support, and words of encouragement. Here's a little video I did of me and my kids getting down the basement.

https://youtu.be/KSoWC-v744I

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Originally Posted by stevewatr

Thanks for all the support, and words of encouragement. Here's a little video I did of me and my kids getting down the basement.

https://youtu.be/KSoWC-v744I

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Basement have good ventilation??
Be careful welding inside your house..fumes and fire danger but I'm sure you know what to do to be safe
I tig weld in my kitchen sometimes...turn the stove vent on and burn metal

Quote:

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Originally Posted by Michael ray

Basement have good ventilation??
Be careful welding inside your house..fumes and fire danger but I'm sure you know what to do to be safe
I tig weld in my kitchen sometimes...turn the stove vent on and burn metal

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Thanks. I'll have to rig up something for improved ventilation.

Steve.

I just posted part 3. I shot this video before I had a chance to print out and see the tech manual Steve (7A749), was kind enough to email me. But using my meter, and the basic wiring diagram in the owners manual, I was able to figure some stuff out. I make a few incorrect assumptions along the way, but in the end I was able to figure out quite a bit.

https://youtu.be/MVIt1D1zloQ

The hum you are hearing is more than likely just the transformer. I haven't ran our 250 at work in quite a while, if I am remembering correctly though it has a hum to it when it's sitting idle and powered up.

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Originally Posted by Dan

The hum you are hearing is more than likely just the transformer. I haven't ran our 250 at work in quite a while, if I am remembering correctly though it has a hum to it when it's sitting idle and powered up.

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Yeah, I kind of over reacted there. Appears to be normal transformer hum, and I'll bet it varies with age as the windings probably "loosen up" over time. I've had older fluorescent lights that were noisier [emoji4]

Go to HTP America, buy a nice swan neck gun for that beast and get to welding. Doesn't seem like there is much else to do...congrats.

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Originally Posted by Louie1961

Go to HTP America, buy a nice swan neck gun for that beast and get to welding. Doesn't seem like there is much else to do...congrats.

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Thanks. I just snapped up a deal on a new Miller M25 off Ebay.

Won't be long now before I'm burning wire......hopefully.

https://youtu.be/99SJLYx-LPg

You should be able to put a smaller liner in for .023 wire and change out the tip to match the wire. Although it's not cost effective for a hobby welder, in theory it would be much easier to have a gun set up for .023, one for .030 - .035 and a third for .045 up to 1/16 for dual shield flux core wire. This way any time you change the wire spool out for your needs you can change the gun at the same time to match the wire and boom you are welding in no time. It makes doing a quick change over for wire and gun easy with out the hassle of fiddling with the liners for a how ever long it takes. .02¢

You are gonna have a very capable welding machine for a killer price as long as the machine performs as it should. :cool2:

You only need one compression spring for the spool hub drag tension. The second larger compression spring is for helping retain a narrower 8" diameter (compared to a 12" diameter) spool of wire on the spool hub. I could pick up an acceptable (doesn't have to be an exact match) compression for the spool hub tension at my local ACE hardware store.

Quote:

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Originally Posted by Dan

You only need one compression spring for the spool hub drag tension. The second larger compression spring is for helping retain a narrower 8" diameter (compared to a 12" diameter) spool of wire on the spool hub. I could pick up an acceptable (doesn't have to be an exact match) compression for the spool hub tension at my local ACE hardware store.

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Thanks Dan

Zombie thread, I know, but stevewatr, did you ever get the 250 running? If so, how did it do for you?