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Thread: Miller dialarc HF

  1. #1
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    Miller dialarc HF

    I recently purchased an old 310 Amp HF.
    I basically saved it from being recycled.
    I have come a long way in resurrecting it.
    The mice had enjoyed living inside for quite some time...
    I have acquired everything I need to attempt to make it work again.
    The first part of the battle had been won. It will stick weld.
    I am venturing into the high frequency tig portion and discovered the points were heavily corroded together...no gap whatsover....I have cleaned the points and I am setting them to .008.
    The next challenge is I see somebody bypassed the small rectangular capacitor?...part #miller 31-602.
    I see it is oozing and nasty and I am wondering since someone bypassed it is there anything else that may be damaged due to someone bypassing it?
    They are a little over $100 and I am getting a little skeptical of putting more and more money into this welder.
    Is there a good chance that this oozing component is all I need to get my high frequency working again?
    Is there a more affordable alternative to this pricy old component that would plug and play?
    I think this welder is from 1975 timeframe...

  2. #2
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    Re: Miller dialarc HF

    That capacitor sets the resonance for the HF circuit. if someone bypassed it I have to image it was to disable the HF start in kind of an awkward way? I am not sure what damage it might have done but my gut says maybe none. However, that being said, it is a sine wave TIG welder. You can buy a half way decent AC/DC inverter TIG welders for under $1000, so you have to really think about how much money you want to put into this unit. It might be better to find another similar welder on the cheap to be parts donor rather than sinking hundreds into new parts that may or may not work, and then you end up with what some might consider a mediocre TIG welder (no balance adjustment, no frequency adjustment, no square wave output, no pulse, etc. etc.) The other approach would be to relegate this machine to stick welding where it really shines the most, and just forget the TIG aspect of this machine.
    Miller Multimatic 255

  3. #3
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    Re: Miller dialarc HF

    I have had no formal training on tig welding. I have been in maintenance for 20 years and all I know is these old machines. Made in America with real copper windings. I don't know these new fancy settings all I know is what a square wave looks like on an oscilloscope.
    I've been taught the basics by old timers. I was then just released into the world to fix things that were in need. I have done a fairly good job of tigging with these old machines. It seems that as long as you have your amperage set right and you keep moving that you can weld without any fancy controls. As it stands I am probably sitting right around the $600 mark for everything, including shielding gas and consumables. I have seen some tig welders out there around a thousand dollars but then I cringe when I discover it's origin and see the crappy circuit boards that will corrode and wither away in a few years of sitting in a non climate controlled pole barn.
    I appreciate the info. I am going to finish up all the obvious things and give it a try as it is and see what it does.
    I have never used an old machine that I didn't like. Maybe some day I will actually take a class and do some backwards learning 🤔..
    Wish me luck.....

  4. #4
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    Re: Miller dialarc HF

    If it stick welds, then you can scratch start TIG weld without the HF.
    What extras came with the welder for TIG ? Leads? Torch? Regulator?
    You will need that and a tank of Argon to get started.
    Last edited by bead-boy; 3 Weeks Ago at 03:20 PM.
    Century buzzbox that I learned on 40+ years ago (was Dad's)
    Crappy Century 110volt mig 70 amp pigeon pooper.
    Lincoln Idealarc TIG-300

  5. #5
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    Re: Miller dialarc HF

    I bought a foot pedal from ebay, torch from a garage sale, new...old stock regulator and used argon tank..I am very resourceful. I tried not to break the bank on the entire outfit. I only paid $100 for the welder.....about 25 cents a pound....I am certainly not going to lose much money...
    Just a lot of work.....had to heat shrink the 50 foot leads....they were way too nice to cut Short. The biggest expense was the old foot pedal I bought....if the capacitor is all I need to get the ac up and running 🏃*♂️ then I will gladly buy one....but it seems they are way overpriced and I should be able to use something else so I don't toss $110 into an old welder....if I buy that capacitor and it doesn't get the high frequency working then I would be putting money into the old welder that I might be throwing away. Everything else I bought for it can be sold or used on the next welder ....so I am at the point where I might be throwing money 💰into components that I might not be able to recoup my cost on. I just want to make researched decisions so I don't throw money at it blindly....$110 or so for a capacitor seems pretty insane to me...especially if it is very old and already susceptible to failure due to the components age. If it gets the welder going to its original design potential then I am OK throwing a little money into it....especially if it runs another 20 years or so....

  6. #6
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    Re: Miller dialarc HF

    Century buzzbox that I learned on 40+ years ago (was Dad's)
    Crappy Century 110volt mig 70 amp pigeon pooper.
    Lincoln Idealarc TIG-300

  7. #7
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    Re: Miller dialarc HF

    Thanks, I ordered up 2 . Now since they were pigtailed together I'm not sure if I need to figure out the polarity or not....I guess since I bought 2 I can always resort to trial and error. I do enjoy blowing things up but I prefer to not unintentionally commit a terrorist act on my own welder. ...what do you think?...the blue wire or the red wire?
    Do mice enjoy negative wires over positive wires?....only one is chewed. He didn't like the other wire.......

  8. #8
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    Re: Miller dialarc HF

    No polarity if its not marked. The real question is : .00024 uf, or .02 uf I think both are available .
    Another thread from another site that never really posted a resolution.

    https://forum.millerwelds.com/forum/...ller-capacitor

    Nothing wrong with an old sine wave AC tig welder, so long as you have the space to keep it, power to feed it , and don't need portability. Can/have you measured the caps for capacitance, the other poster said his ran, but the caps were oozing .

    @ Bead-Boy - Thanks for posting that link, I was surprised to find none of my usual electronics part sources had any of the parts. Looks like a part from a wwII vintage radio. Never heard of All Electronics before , but after looking at their site , I will be using them. They seem to have a lot of old stock items that DigiKey , Mouser, AlliedElec, and Newark electronics no longer carry.

    good luck with the machine

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    Last edited by albrightree; 3 Weeks Ago at 12:43 PM.
    Airco 250 ac/dc Heliwelder Square wave
    Miller Synchrowave 180 sd
    Miller Econo Twin HF
    Lincoln 210 MP
    Dayton 225 ac/dc
    Victor torches
    Snap-On YA-212
    Lotos Cut60D

  9. #9
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    Re: Miller dialarc HF

    Quote Originally Posted by Darin1925 View Post
    Thanks, I ordered up 2 . Now since they were pigtailed together I'm not sure if I need to figure out the polarity or not....I guess since I bought 2 I can always resort to trial and error. I do enjoy blowing things up but I prefer to not unintentionally commit a terrorist act on my own welder. ...what do you think?...the blue wire or the red wire?
    Century buzzbox that I learned on 40+ years ago (was Dad's)
    Crappy Century 110volt mig 70 amp pigeon pooper.
    Lincoln Idealarc TIG-300

  10. #10
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    Sep 2021
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    Re: Miller dialarc HF

    I wish I would have done my homework rather than jumping at the" suggested" part that cost $3.50 each...I was bamboozled.
    They cost me $15.50 and I can hang em on the wall and remember that haste makes waste. They are not the correct value. I got caught up in the excitement of a reasonably priced solution.
    I did manage to find a few that should work but they aren't here yet.
    If they work I will post the manufacturer and part numbers for others to use.
    For now I will sit back and luck my wounds.....

  11. #11
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    Re: Miller dialarc HF

    Just looked at the DialarcHF (1980) Manual - Item #127 C2 Capacitor, Mica .002 uF 5000 VDC

    .002uF = 2000pF ?

    https://www.surplussales.com/capacit...sB-E-CCap.html

    Manuals can be found for free at Millers website : https://www.millerwelds.com/support/manuals-and-parts

    Have you verified the capacitance of the existing caps yet ? Then verified the rest of the wiring to the capacitors/HF circuit ?

    Check twice, buy once.

    Good Luck
    Airco 250 ac/dc Heliwelder Square wave
    Miller Synchrowave 180 sd
    Miller Econo Twin HF
    Lincoln 210 MP
    Dayton 225 ac/dc
    Victor torches
    Snap-On YA-212
    Lotos Cut60D

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