New Toy.. No DC welding.. AC Welds good - Help Please
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  1. #1
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    Nov 2016
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    New Toy.. No DC welding.. AC Welds good - Help Please

    Good evening friends,

    I picked up a 1968 Lincoln Idealarc 250 AC/DC machine today. Got it home and found that there is no current for DC welding.. AC will weld just fine.
    Upon removing the covers, it looks to me as if there is a part or parts missing from the back just above the fan. There are (as best as I can describe) flat metal that is bendable connectors with holes machined into them that look like 7/16th holes. There are 4 of these (see pictures)

    They are attached to nothing but look as if they once were attached to something. I believe that this may be the issue. However, I do not know what to attach them to... Any help would greatly be appreciated. Any advice is always welcome.

    I have attached pictures.. can take more if needed or can provide further details.

    Thank you and I always appreciate your help.

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  2. #2
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    Appears to have the Deleted Rectifier option.
    Go to Lincolelectric.com and punch in the model and code numbers and you might be able to bring the prints up.

  3. #3
    Join Date
    May 2010
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    ct.
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    What do the other ends of those straps go to?
    Could those straps be the conductors to that rectifier
    assembly?
    I don’t see anything connected to rectifier assembly.
    Maybe rectifier is shorted and was disconnected for
    testing or for AC welding.
    Miller a/c-d/c Thunderbolt XL
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  4. #4
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    Nov 2016
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    Now that I see what the rectifier is.. (learning curve).. it is the connectors to the rectifier.. So, just re-attach? .... What should I look for that could be a prblem with the rectifier?

    Thank you
    Kell

  5. #5
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    Sep 2012
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    West of Minnesnowta, USA
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    Quote Originally Posted by Virgil5 View Post
    Go to Lincolelectric.com and punch in the model and code numbers and you might be able to bring the prints up.
    Did you do this? If not, it would be a good place to start.

    Quote Originally Posted by jpump5 View Post
    Maybe rectifier is shorted and was disconnected for testing or for AC welding.
    The rectifier is probably shorted and that is why it is disconnected.

    Quote Originally Posted by kjemison1966 View Post
    Now that I see what the rectifier is.. (learning curve).. it is the connectors to the rectifier.. So, just re-attach? .... What should I look for that could be a prblem with the rectifier?
    What do you have for electrical test equipment and experience? The rectifier should be tested. If you reattach and it is shorted, the welder will GROWL at you vs that nice 60 Hz hum. And hopefully not do any (further) damage.

    There should also be a capacitor or several associated with the rectifier. If they are bad, that can cause premature failure of the rectifier. More curves to add to your learning. Good luck.
    Tim

  6. #6
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    Is it obvious from looking at it where straps were
    originally connected?(I.e. little or no chance of
    incorrectly reconnecting it).
    I would want to test the rectifier assembly first.
    Do you have a multimeter?
    I’m thinking someone disconnected it for a reason.
    Miller a/c-d/c Thunderbolt XL
    Millermatic 180
    Purox O/A
    Smith Littletorch O/A
    Hobart Champion Elite

  7. #7
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    Nov 2016
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    121

    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    Thank you for the help, I do have a schematic but not real good at reading it yet... I do have a multimeter ... What should I look for and how to test.?

    Kell

  8. #8
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    May 2010
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    ct.
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    Diodes are like check valves. They should conduct much better in
    one direction than the other. With multimeter set to ohms you
    would measure ohms across diode, swap leads and repeat.
    Miller a/c-d/c Thunderbolt XL
    Millermatic 180
    Purox O/A
    Smith Littletorch O/A
    Hobart Champion Elite

  9. #9
    Join Date
    Oct 2009
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    Austin TX
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    800

    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    Don't connect the rectifiers until you have checked them out with an ohm meter to verify they are ok. The previous owner would not have disconnected them if everything was working properly. The replacements should not be too expensive.
    Miller Syncrowave 350
    Millermatic 252/ 30A spoolgun
    Miller Bobcat 225g w/ 3545 spoolgun
    Lincoln PowerArc4000
    Lincoln 175 Mig
    Lincoln 135 Mig
    Everlast 250EX Tig
    Century ac/dc 230 amp stick
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    Hypertherm 1000 plasma

  10. #10
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    Nov 2016
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    121

    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    Good evening,
    The image that you see here... is this the diode? The black circular thing...The cable strap on the left feeds through a hole and to the back of the machine. It is one of the unattached connectors (see above photos on first post)

    Thank you for all the help.. it is appreciated!

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  11. #11
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    Here is another image clearly showing the back of the machine... as you can see, the 4 strap type connectors that are coming through the hole in back of machine are not connected ... the little square box above the rectifier looks to have a diode and 2 wires on each side that are not connected.

    I hope this helps and clarification on troubleshooting will be better.
    Thank you
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  12. #12
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    Nov 2016
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    Update,

    I think I need one of these diodes or maybe 2 ? (see link below) I don't know how many I am supposed to have..or, how to wire them up. The schematic I have from the manual is not very clear on this. Advice is appreciated!
    https://www.ebay.ca/sch/i.html?_from...All-Categories

    Thank you
    Kell

  13. #13
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    May 2010
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    If you look at the second pic. of your first post,
    there appears to be 6 diodes visible,3 attached
    to one plate and 3 to the other. I’m guessing
    there are 6 more not visible in pic.(?). That assembly
    of plates,spacers,diodes etc. is what I’m referring
    to as the “rectifier assembly”. In the
    schematic drawing, each group of 3 diodes may
    be represented as one diode.
    Miller a/c-d/c Thunderbolt XL
    Millermatic 180
    Purox O/A
    Smith Littletorch O/A
    Hobart Champion Elite

  14. #14
    Join Date
    Jun 2014
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    Southern Illinois
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    In image 5 the black circular thing is a thermal protection device that shuts the welder down in a overheat situation. Your welder has the old selenium diode rectifiers, the newer idealarcs from the mid 80's or so use silicone diodes. There are threads on here that explain how to update to the newer style, more available and cheaper. And the item in the last picture above the rectifier assembly with the 2 wires is a voltage suppressor, if your open circuit voltage is to high at the output lugs, this has failed.

    Here is the newer style rectifier board from a 1989 Idealarc 250
    https://uploads.tapatalk-cdn.com/201...b31821a65c.jpg


    Sent from my iPad using Tapatalk
    Steve

    Miller Dialarc 250 (1990)
    Miller Maxstar 140 STR (2003)
    Lincoln SA200 Redface Pipeliner (1966)
    Lincoln MP210 (2015)
    Victor and MECO torches

  15. #15
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    Nov 2016
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    Thank you for the info Steve! .. I will look into converting the system to the new Silicone diodes. I guess what I really want to know before I convert is... will the welder perform better with the Silicone diodes?

    Always appreciate the advice!
    Kell

  16. #16
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    I can’t really speak to how much better it will weld. I’ve welded with lots of both and I can’t tell a difference. The newer style are cheaper to buy and replace if ever needed. Unless you could find a damaged machine that you could buy the old style rectifier board cheap, update. They are great machines. Here’s my 1989 model I found a few months ago. I got it from the original owners family. It was in almost new condition
    https://uploads.tapatalk-cdn.com/201...d3f4a38e66.jpg


    Sent from my iPhone using Tapatalk
    Steve

    Miller Dialarc 250 (1990)
    Miller Maxstar 140 STR (2003)
    Lincoln SA200 Redface Pipeliner (1966)
    Lincoln MP210 (2015)
    Victor and MECO torches

  17. #17
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    Nov 2016
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    121

    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    Steve, that is a nice looking machine!

    I thought about it over night and I think I would really like to keep it all original if possible. I will spend some time today looking for a rectifier with the selenium diodes for this welder. I uploaded a few pictures.. The cleaner one is a 1984 model and is the same type of welder I went through school with in 1984. It welds sooooo nice!
    The other 250 is from 1968.. All the panels are perfectly straight and not all beat up with dents etc.. I bought from a nice kid. He said his uncle owned it from new and for the last 10 years or so just sat in the corner of his garage. His uncle passed away about a month ago and he had no where to keep it. Once I fix the rectifier and test it.. then I will go ahead and sand down the metal, prime and paint it. I wonder if I can still get the original color red? Anyway, I appreciate all the help... Learning a lot which is always good!
    Have a great day!
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  18. #18
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    Both look good Kell. As far as painting, the ones we restore that have good straight sheet metal. Go to a powder coater in your area and get a price for them to sandblast and powder coat. It will save you s bunch of time and money. We have ours zinc primed and then coated for less than $150. They turn out really nice


    Sent from my iPhone using Tapatalk
    Steve

    Miller Dialarc 250 (1990)
    Miller Maxstar 140 STR (2003)
    Lincoln SA200 Redface Pipeliner (1966)
    Lincoln MP210 (2015)
    Victor and MECO torches

  19. #19
    Join Date
    Nov 2016
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    121

    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    Hi Steve,

    I'm in luck! There is a powder coater about 1 mile from my shop.. I will take the pieces to him and see what we can work out. On another note, it seems as if I am striking out on finding original parts for this machine (1968)... I will probably got to the conversion and just be done with it. Sometimes you just have to do what you need to do ... Would you say that the "red" on the original machines actually have a little orange in them ...?? or , are they just red?
    Thank you
    Kell

  20. #20
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    Southern Illinois
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    That was the old Cinamon red. The newer machines are more like International red. If you want to really be accurate you can call Lincoln and they can give you the paint code for both.

    As to the rectifier board, one place you might call is Stumpf’s Welding in Mascoutah, Illinois *(618) 566-4733‬ they have been a Lincoln dealer since 1952 and have lots of parts and knowledge. Ask for Jim if you call,he’s been there since 1971


    Sent from my iPhone using Tapatalk
    Steve

    Miller Dialarc 250 (1990)
    Miller Maxstar 140 STR (2003)
    Lincoln SA200 Redface Pipeliner (1966)
    Lincoln MP210 (2015)
    Victor and MECO torches

  21. #21
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    Nov 2016
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    121

    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    Steve,
    I must really say that you are awesome! Thank you do much for the tip! .. I will call them tomorrow.

    Appreciate your help as always!
    Kell

  22. #22
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    No problem and good luck


    Sent from my iPhone using Tapatalk
    Steve

    Miller Dialarc 250 (1990)
    Miller Maxstar 140 STR (2003)
    Lincoln SA200 Redface Pipeliner (1966)
    Lincoln MP210 (2015)
    Victor and MECO torches

  23. #23
    Join Date
    Mar 2010
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    Ceres, California
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    The diodes on the heat sink are silicone. Press fit diodes soldered to the plate. Have been obsolete for many years.
    You have a couple of choices. Replace just the shorted group with one stud diode or replace all 4 at the same time.
    You can buy a rectifier assembly that fits in the current welders. and mount that in there.
    If it wasn't lost. there is a thread with pictures on one way to convert to stud mount diodes.
    You can get to the Lincoln service book site. its now open to any one. Go to Lincolns main site.
    Then the support tab, select parts and wait for it to open. once there enter the code number and it will take you to the parts and service information. If the code number is gone you can work your way through the picture tree.
    To your welder. You will have to look at several to find the one that matches your machine code.

  24. #24
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    Nov 2016
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    Good evening,

    So... be patient with me.. new to this electrical stuff... I have attached a photo with arrows. I called Stumpf's Welding repair today and the gentleman was doing his best to explain how to check the diodes. He said typically one will be faulty and that I would just have to replace one with a new circular type diode. He said that I should "touch" the diode with one lead from my multi-meter in "diode mode" and the other lead to the connector. As you can see by the red arrows, there are 2 connectors for each side separated by a very small gap. My question is this.. is the diode the plate that the black arrows are referencing? and is the connector he is talking about the one's referenced with red arrows? ... Then he wanted to know about weather or not it was the "tail" of the diode..? (I have no clue).. said once I figured this out he could sell me the correct replacement diode. Any help / guidance would be greatly appreciated!
    Thank you
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  25. #25
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    Re: New Toy.. No DC welding.. AC Welds good - Help Please

    Update...So, I figured out that I had a faulty multi-meter.. bought a new one...now I see if I touch the back plate on the left side with my RED lead and the BLACK lead I touch the left rear connector.. I get a reading of 466 on my multi-meter. If I switch the leads around I get OL on my multi-meter display.

    Now, move to the front left plate and connector. I touch the RED lead to the connector and BLACK lead to plate.. I get a reading of 452 and when I switch them I get OL on my multi-meter.

    Right side

    Rear plate and connector on right side: Rear connector I touch with BLACK and plate I touch with RED I get a reading of 469 and switch the leads I get OL on multi-meter

    Front plate and connector on right side: Front connector I touch with RED lead and plate I touch with BLACK lead I get a reading of 456 and when I switch them I get OL on multi-meter.

    My guess is with knowing what little I have learned in the last week... this means that the diodes are working properly... What do you all think?

    Thank you
    Kell

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