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Thread: Miller 250 AC/DC HF Restoration and Manual assistance please.

  1. #1
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    Miller 250 AC/DC HF Restoration and Manual assistance please.

    Just picked up this unit for a mere $75. It is an Airco, but i know it's the same machine as the Miller 250 AC/DC HF. Now I am attempting to make it function. It came with no cord, leads, torch,pedal. I have removed the case and blown it out, nothing appears burnt, no leaking caps, BUT the amperage control does not move. I am hoping that the sliding core in the transformer is just sticky from a long period of storage and not welded together...any manuals and advise is greatly appreciated.Name:  wel3.jpg
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  2. #2
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    Welcome to the forum.

    Model# 2.5A/DDA-24-HF-B or 2.5A/DDA-24-PHF-B?

    SN?
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  3. #3
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    Model# 2.5A/DDR-224-PHF-B
    Serial# P349413

  4. #4
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    224 or just 24? Should be just 24.

    I suggest you contact Miller Customer Service (920-734-9821) with your Model/SN and ask if they'll email you form SPM-312 and Circuit Diagram No. A-592-A03 (that should be adhered to the inside of the housing wrapper).
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

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  6. #6
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    I found the amperage control issue....someone welded these tabs and installed a setscrew on each side locking the amperage setting. Why on Earth would someone want to do that? This unit came from the local high school...Name:  setscrew.jpg
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  7. #7
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    I stand corrected on the Model No.. Perhaps my info is a misprint. ???

    On the "fixed" amperage setting, if it came from a high school perhaps the teacher fixed it at that setting for a specific material that he/she taught (if you could call it that) welding technique with. Who knows? Your guess is as good as anyone's.
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    Thanks Duane. Will be getting in touch with miller one of these days. Gotta go pick up a plug and make a cord. Flip the switch and see if it's worth further investment(ground, stinger, torch, and pedal. I'm so exited....like a fat kid in a candy store!
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    I understand your excitement. I just bought a Dialarc HF.

    Hey Duane, your PM space is full.
    Gravel

    The difference between theory and practice is that in theory there is no difference.

  10. #10
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    Quote Originally Posted by Gravel View Post
    Hey Duane, your PM space is full.
    Should be good now.
    Thanks.
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  11. #11
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    I'm going to wire the beast directly to the breaker box. I am thinking 100A breaker and 4/3 wire. Overkill or just right??? I hear these are pretty power hungry.
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  12. #12
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    My Dialarc HF will run full out on a 60A breaker but I don't know how long.
    Hard wire on a 100 w/#4 will be nice.
    Gravel

    The difference between theory and practice is that in theory there is no difference.

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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    Hi Christopher! Nice catch!
    I have one of the same model on its way that I have never seen up close. Is the fitting on the lower right Argon output and the one above input?
    What is behind the caps for water in+out?
    Thanks,
    Fred

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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    Quote Originally Posted by fred g View Post
    Is the fitting on the lower right Argon output and the one above input?
    Yes.

    Quote Originally Posted by fred g View Post
    What is behind the caps for water in+out?
    Nothing as it doesn't have the optional valve for a water cooled torch.
    MM200 w/Spoolmatic 1
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    Hi Christopher,
    These will last forever. I just noticed that this one seems to have the selenium power rectifier, that could go bad over time.
    Things to look for are leaking caps on the HF, relay contacts wearing out (one is 24V DC and I think the other is 24V AC) and replacing the smaller selenium rectifier that controls the "start" mode of HF with a simple 50A bridge. Gotta love that massive switch they use to turn it on- looks like a standard light wall switch, except huge! While doing repairs I fired mine at night and when I hit that switch there were definitely some sparks just turning it on.

    Keep in mind that the HF control start plug (upper right) must have the pins shorted for HF to fire on this machine.

    Got mine for $100 with a cart and 50 feet of 6-3 SOOW, so it was worth the money just for the cord.
    Enjoy,
    Tim

  16. #16
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    Been a while and thought I'd post an update. Rigged the unit with a temporary cord and fired it up. Everything is working so far..well at least on the DC, I have not even tried AC yet. Burns rods clean and smooth. Scratch start tig works well. Only real issue I have is the gas solenoid seems to be stuck open. It just blows gas all day. Just picked up some nice long leads for it. Now I can stick anywhere in the driveway. Working towards doing some AC tig once I get everything worked out. Anyone have a spare gas solenoid for these things?

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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    Well, the timer never moves, but if I turn in to zero I the solenoid closes. It appears someone has put a pair of pliers to it once before so it's the obvious culprit. When I get some time I'm gonna open the case and poke around with my meter and be sure relays are all good. Then hopefully get some flea bay parts and be good to go. Thanks for the info.
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    I picked one of these welders up last Sunday. Got everything cleaned up and wired in. Was able to get a nice weld in AC/DC-/DC+. The caps for the HF section have oozed out, so I've got replacements order for that. I don't believe the HF works as it should be. (I did set the arc gap though) Anyhow, I'm setting this unit up as a workhorse for everything around the house/shop. I have a TIG torch setup on the way as well as a regulator. Going tomorrow to look at/buy a cooler setup for it as well.

    Anyhow, I'm sure I can get the HF stuff sorted. The torch I bought has a switch on it as well. But my real question is, can a pedal be retrofitted into these units? I see the Miller RFC-23A is the pedal of choice for the Dialarc 250. But I know there's no provision for remote current controls on this unit. Is there a means of adding it to this welder? Or has anyone split up the internal wiring to feed 110V to the HF side and Low voltage to the gas solenoid. (Alternatively, I could swap out the solenoid to a 110vac I guess) I've been reading about SSVR's which I could use a 10K foot pedal to control and vary input voltage to the transformer that way. But I'd be more interested in constructing something "factory" for it.

  19. #19
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    So I was able to find a parts manual on this welder. Luckily it has a schematic at the end.

    Here's the factory wiring:
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    Now, I've purchased a SSVR setup to control it. It uses a 10k ohm pot, which happens to be the same value as all the TIG inverter welders from china. So I'll use one of those to control it.

    So this is what I've come up with so far on how to adapt a pedal. I also plan on adding a DPST switch as well. One side of the switch will revert from foot pedal to a 10K resistor to allow the welder to be switched between normal and pedal mode. The other side of the switch will be used to power the 110v circuit tapped from a leg and neutral. But I'm trying to figure out how I need to make this happen from the schematic. I see from the schematic there's a tap on the welder side of things at 25 and 28. I know TD1 is the timer for postflow as well. I will use the microswitch to plug into the remote HF start on the pedal. (RC1) I'm just trying to figure out how to feed the Gas solenoid/timer/HF side of things 110v but still work the relays. Any thoughts?

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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    Oh and I understand the varying the input voltage will mean the dial will still set the upper limit output. So if I set it to 150 amps, full pedal will only deliver 150 amps.

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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    4 wire seems like overkill to me. I am running 6 wire with a 100 amp breaker. I can't imagine the dialarc draws any more than a sync 250.
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    Quote Originally Posted by Louie1961 View Post
    4 wire seems like overkill to me. I am running 6 wire with a 100 amp breaker. I can't imagine the dialarc draws any more than a sync 250.
    Dunno, It isn't a Dialarc. I'd check the nameplate, or the manual.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

  23. #23
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    No, it's not a Dialarc, it's just an HF 250.

    Probably calls for 100+ amps for full!power operation.

    Best guess without looking it up.

  24. #24
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    Re: Miller 250 AC/DC HF Restoration and Manual assistance please.

    Because it came from a high school and they didn't want the kids messing with it I imagine. That gets done alot where shops, etc. don't want operators messing with settings, speeds, feeds and so on

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