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old miller dynasty 200. found the problems, trouble finding the parts!

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  • Irritantno9
    replied
    My guess, and this is probably wrong is that the Semikron Skiip module has failed. I have bought the caps to replace mine, and I have done all the pre checks.
    I could find nothing wrong with any components during those tests. At some point I may pursue this, but I have not had the time. My sincerest guess is that most older dynasty welders you will find for cheap may suffer from similar problems. Unless you have nothing to lose, I would tend to follow what Cruizer says. I did originally perform a repair on my welder that was preventing the foot control from working. Cruizer was very discouraging about any attempt to repair it. It worked out fine for me. But this is a little more expensive as the caps are $50-60 each and the semikron is ~$300. (thats more than I paid for the thing)


    I suspect that the Semikron fails and passes AC into the board and the caps cant handle that. I'm just reluctant to spend any money on a 10-12 year old welder that was plagued with early design issues.
    Last edited by Irritantno9; 05-29-2016, 05:02 PM.

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  • Aeronca41
    replied
    Never heard of buzzing resistors. Seems like that would require some very high current, either pulsed or AC. Looks like you're going to need a miller service tech. Perhaps Cruizer will see this and have some words to help.

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  • spriggan
    replied
    Bump from the dead, had the capacitors and 4 small resistors replaced by a company called psi, upon starting the welder their is a loud buzz from the resistors...any help?

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  • H80N
    replied
    Originally posted by spriggan View Post
    i have soldered circuit boards before but to be honest i cannot get these capacitors off! i have a gas soldering gun…still, this is a pain. i will looking into more information when i have the time. usually when i get off work at 1030pm I'm not up to try anything with this board.

    will check out that site and report back.
    Still concerned that you might be taking a dubious path in this repair effort..

    BUT... as far as removing components like large caps..

    you may need to resolder with a high quality 60/40 rosin core solder and "Solder-Wick" the joints a few times before it will draw out all of the solder from the joints... PC boards are easily damaged and overheating can lift the copper traces..

    some prefer a "Solda-Pullit".... I think the Wick is gentler on the boards..

    Have some real concerns about using a gas soldering iron for this process... a 100 Watt + sized electric iron would give you more control..

    Have included a couple of "Solder-Wick" pics for those not familiar... it is available in several sizes.. the larger ones would be most favoured in this application..
    Attached Files
    Last edited by H80N; 06-08-2015, 08:05 AM.

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  • spriggan
    replied
    i have soldered circuit boards before but to be honest i cannot get these capacitors off! i have a gas soldering gun…still, this is a pain. i will looking into more information when i have the time. usually when i get off work at 1030pm I'm not up to try anything with this board.

    will check out that site and report back.

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  • H80N
    replied
    Ask Cruizer.....

    Originally posted by H80N View Post
    Have a feeling that the visible failures that you have observed are probably a result of another failure upstream...

    If you could post your serial number... hopefully.."Cruizer" can give you more advice...

    For many of the parts try these guys

    http://miller4less.com/

    after you have looked up the numbers in the Miller parts book.. found here..

    http://www.millerwelds.com/service/ownersmanuals.php
    You might want to read this thread and others that are similar..

    http://www.millerwelds.com/resources...lown-capacitor

    and again... hopefully Cruizer can give you some machine specific troubleshooting advice.... he speaks from experience...

    would hate to see you wasting time and money by just replacing parts that appear visibly defective... while the root cause is elsewhere...

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  • Guest's Avatar
    Guest replied
    The topic I explain here has been used with VFD drives. The same kind of electronics
    exist in your welder. Look up what capacitor reforming does. People do it to repair
    capacitor components. I think in the welding world people don't know anything about it.
    Anyway, look it up. You might learn a little about your capacitors. I briefly looked up
    some on the digikey website, some cost close to $100 each.

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  • Guest's Avatar
    Guest replied
    Originally posted by spriggan View Post
    well, received the capacitors from mouser, they are rated at 400volts not 450 like the panasonic ones.

    I'm confused here again…on the older panasonic capacitors it says 450volts. i am told that is the "VDC working" amount BUT panasonic does not offer a capacitor of this size and nano-farad rate with a 450volt run amount, only a surge amount…I'm assuming the older capacitor is showing the surge amount and the new capacitor is showing the normal operating amount?

    the new capacitor is smaller in size, same nano-farad(1500), but labeled 400volts. both 5 pin snap on.

    mouser does not offer what I'm looking for in a 5 pin, only 4 pin...

    thoughts on this anyone?

    edit: every time i call mouser i learn more information…the 5th pin may just be a guide pin. i will need to take them off the circuit board and see if thats true, anyone know if that is true?
    Your assumption is wrong. The newer ones probably are not going to be equivalent.
    If you use them you will lower the margin of safety.
    And it is not "nano" but "micro-farad". Nano means 10 with a exponent = -9.
    Micro means 10 with a exponent = -6. 1500uf is what you mean.

    If you lived close to me I would help you take a look at it. At the very least you
    should look at what www.Digikey.com has to offer.

    You will be graded by some of the members here on what you do. You will get a high grade
    if you buy the parts from Miller or send in your machine and have them fix it for a few thou.
    A low grade will be given if you identify a problem and find a better part and fix the problem yourself.
    Last edited by bluesky; 06-03-2015, 01:44 AM.

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  • spriggan
    replied
    well, received the capacitors from mouser, they are rated at 400volts not 450 like the panasonic ones.

    I'm confused here again…on the older panasonic capacitors it says 450volts. i am told that is the "VDC working" amount BUT panasonic does not offer a capacitor of this size and nano-farad rate with a 450volt run amount, only a surge amount…I'm assuming the older capacitor is showing the surge amount and the new capacitor is showing the normal operating amount?

    the new capacitor is smaller in size, same nano-farad(1500), but labeled 400volts. both 5 pin snap on.

    mouser does not offer what I'm looking for in a 5 pin, only 4 pin...

    thoughts on this anyone?

    edit: every time i call mouser i learn more information…the 5th pin may just be a guide pin. i will need to take them off the circuit board and see if thats true, anyone know if that is true?
    Last edited by spriggan; 06-02-2015, 12:49 PM.

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  • Guest's Avatar
    Guest replied
    Originally posted by spriggan View Post
    so blue do you think I could pick better components or is that just causing a ripple effect down the line of better parts needed to support, "upgrades"?
    I think the fact that filter capacitors that leak are out of our control. Unless you check them
    regularly and re-form them when you see an issue. That is something I would not do myself.

    With the resistors I see that there are two sets of two resistors in series. The the two sets
    are in parallel. For a 150K ohm value for all four your circuit has the equivalent impedance
    of 150K with the power distributed among four smaller components. I was trying to suggest
    to you that if this was a bleeder resistor you may consider replacing with a slightly larger
    power rating. The burn marks on the circuit board is not good. Since Miller will probably
    not publish the circuit diagram I cannot say for sure what those resistors do, You should
    not have a problem to trace out what they are connected to and decide for yourself. Since
    the resistors are so close to your filter cap that was my first guess.

    In case you don't know, a bleed resistor discharges a high voltage capacitor after the
    power is removed, but it's time constant is not so short as to burden the charging time.
    It is a safety issue with regard to the service person.

    Not to keep going on and on with this but one thing you should do is thoroughly clean that
    board, it needs it. And find out what the purpose of the resistor array is, see if you can
    get the next higher power rating. Ask Miller. You can email me a drawing of that part of
    the control board schematic if you want. I can give you my opinion I don't think it would be
    good to publish it here.

    Leave a comment:


  • spriggan
    replied
    so blue do you think I could pick better components or is that just causing a ripple effect down the line of better parts needed to support, "upgrades"?

    Leave a comment:


  • Guest's Avatar
    Guest replied
    Originally posted by H80N View Post
    an X-Spurt...???.... ... Ho-Boy... now second guessing the design engineers...
    The "H" in H808 must stand for Hijack. You are now on my ignore list.

    Leave a comment:


  • H80N
    replied
    Originally posted by bluesky View Post
    The capacitors are DC used for holding the DC bus in pulse width modulation
    power converters. The resistors have a value of 150K and looking at the trace paths
    on the board it looks like an attempt to use lower power rated components to meet
    a higher power rating. If they are for bleeding the caps, maybe. I wonder if you could
    have done better with a selection here when I see the heat stress areas caused by
    the resistors.
    an X-Spurt...???.... ... Ho-Boy... now second guessing the design engineers...

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  • Guest's Avatar
    Guest replied
    Originally posted by spriggan View Post
    the large can aluminum electrolytic capacitors have crapped the bed. literately dropping its liquid contents on the board. i took the boards off the machine to find it also has 4 burnt resistors.

    large can aluminum electrolytic capacitor:
    ECEP2GP152HA

    now with the resistor, i do not understand which code to use for the 3 digit "packaging" end code. there are, "lead(pb)-free" and "tin/lead"
    Resistor:
    CPF3150K00FK_ _ _


    ryan
    The capacitors are used for holding the DC bus in pulse width modulation
    power converters. The resistors have a value of 150K and looking at the trace paths
    on the board it looks like an attempt to use lower power rated components to meet
    a higher power rating. If they are for bleeding the caps, maybe. I wonder if you could
    have done better with a selection here when I see the heat stress areas caused by
    the resistors. BTW, I have designed and built converters.

    You will probably find that the lead free parts cost more.
    Last edited by bluesky; 06-04-2015, 07:56 AM.

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  • spriggan
    replied
    Originally posted by H80N View Post
    My first guess and first choice for an electronic repair solder would be

    "Kester 60/40 Rosin Core" ...

    (60% Tin 40% Lead)

    thank you that is correct, just called miller to verify…sourcing part numbers now...

    found both on mouser.com, very helpful service


    the capacitor #
    661-EKMH401T152MB80T

    resistor #
    71-CPF3150K00FKR36

    will be updating when they arrive

    edit: mouser is out of the resistors, trying to find them at http://www.questcomp.com/
    Last edited by spriggan; 05-27-2015, 11:22 AM.

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