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Need advice on testing a used 1990 Dialarc 250 AC/DC, no High-Frequency

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  • Need advice on testing a used 1990 Dialarc 250 AC/DC, no High-Frequency

    I am not familiar with the Dialarc units and need advice on testing one before buying.

    I have the manual, (OM-314K = JK674521). Welder is plugged in, and can be tested.
    It was used in a shop, it is now owned by a hobbyist, stored in a garage.
    I will use it for stick welding on things like attachments for my skid-steer, ¼ inch plate and larger.
    It will be occasional use, not daily use in a welding shop.

    I have some 6013 electrodes:
    1/8” = 80 – 130 amps; Dialarc low range = 35 – 155 amps
    5/32” = 150 – 190 amps; Dialarc high range = 90 – 265 amps

    After the basics, checking for damage, bad cables, mouse nests, etc.
    If I can burn a rod on AC high & low and DC high & low, is that it? It either works or it does not?
    What are the common maintenance or failure issues with a Dialarc?

    Thank you for your help. Stefen

    Just to clarify the heading, the unit does not have High-Frequency, not that it is broken. When you make a typo in the heading, you cannot edit, changing 'no' to 'not.' Oops.
    Last edited by Stefen7; 08-15-2016, 06:56 AM.

  • #2
    No responses from Dialarc users; will try to help. Never used a Dialarc but looking at the schematic there is not a lot to go wrong. The Range switch contacts could be worn or burned, I'd look at the current adjust rheostat for damage or overheating, and as you mentioned, other internal signs of damage or overheating. Check the welding cable receptacles on the front-if they got loose somewhere along the line, or the cables weren't plugged in tightly, they could be damaged from overheating. Make sure the fan runs, and power input jumper connections are correct for the input voltage being used. As long as the transformer and mag amp (the other thing that looks like a transformer) are OK, pretty much everything else seems like it would be an easy fix if required. If it welds OK, I'm guessing it's probably OK. Hope it works out for you. I think you can count on it being heavy and a bit power hungry. :-)

    Perhaps someone one with more direct Dialarc experience will have some other input.


    • #3
      Once again Aeronca41, I thank you for your input. Dialarcs are known as reliable, but as Tarry99's problem last week shows, there can be issues that are difficult to troubleshoot. Those are the ones I am searching through past threads looking for so I have a heads up.

      As an aside, I made an offer on the Model 61M and am waiting for the seller to reply. I'm hoping to save it from the scrap pile.


      • #4
        Understand. I think his problem was a bad contactor? Not a big deal to replace. Last time I replaced one (in a commercial air conditioning system, which was very similar or identical to those in welders) I think it cost me $58 or $68. You don't have to buy contactors from welder companies; you go to the local electrical supply house and buy what is called a "definite purpose contactor" with the appropriate number of poles, contact current/voltage rating, and coil voltage. Same with switches if you are careful to get the correct ratings. May have to mess with lugs on cables, mounting, etc, to get a generic to fit, so it's worth considering the factory original if the price is close and it's still available.

        Other failures? Any welder could have diodes fail, just like any car could get a flat tire, but they are more reliable than moving parts like contactors, fans, and switches. Even transformers can fail, but most just go on forever (unless the fan fails, you continue to weld, and they burn up). Of course, if they do, the welder is junk unless you can find a donor machine. The Dialarc is made of very low failure rate parts, with very simple circuitry, so is super reliable. Probably more parts in a square inch or two of a modern welder circuit board than in the whole Dialarc.

        Anxious to hear about the vintage model 61. That is just cool! (Speaking of transformers just going on forever...)


        • #5
          Which is why I love the old machines...flip the switch, the fan and power light comes on, there's a happy little hummmmmmmmmmmmm coming out of her....makes me smile.


          • #6
            Originally posted by ryanjones2150 View Post
            Which is why I love the old machines...flip the switch, the fan and power light comes on, there's a happy little hummmmmmmmmmmmm coming out of her....makes me smile.
            ...And that is really the truth, which is why I have 'em, too. On the other hand, the features and capability of my Dynasty200 are awesome, it's just that you worry about the potential for a thousand dollar plus failure. The old Thunderbolt, and machines like the Dialarc, not so much. Just not going to happen. And, most anything that might fail is no big deal to fix.


            • #7
              Yup and yup.


              • #8
                Thank you for the input. This one was 4 hour drive from my home. Someone else was closer and got there first, so I am still looking. Even worse, the seller’'s computer was compromised, my email was hacked & hijacked, and then it moved into MY computer. Long story, not funny, I spent the past several days doing damage control, trying to clean my computer, closing email & PayPal accounts, notifying financial, etc. NOT good.

                As for the discussion of capability / complexity / reliability / portability / cost, that can be a tough decision, and really depends on each user’s circumstances. I decided the Dialarc is in the ‘sweet spot’ between simplicity & reliability vs capability. The (relatively) low-cost power and reliability of a transformer unit, with the ability to vary the amps during welding with a ‘Hillbilly Remote’ if I set up scratch-TIG. That cannot be done on the more basic / reliable hand-crank units like the Miller Two-Fifty or Lincoln Idealarc. A relatively simple Dialarc avoids the complexity and reliability issues of a more capable unit. I am also (relatively) confident buying a 30 yr old welder that can in many cases be repaired by the owner with readily available parts. I did not even consider the Airco Heliwelder V when it came up for sale (still unsold after 1 month), because it is very complex, and no longer supported by ESAB. One part fails, and it is junk.

                But I will be spending most of my time doing carpentry, or moving dirt with a Skid-Steer. My welder will be for maintenance, repair and other occasional tasks. For those welding on a daily basis, $5000 or more for a welder is just the cost of doing business. A shovel and wheelbarrow are cheaper and more reliable than a backhoe, but no one would hire you to excavate a basement.

                Thanks to all for your input, and may your welders keep functioning.

                Note to Aeronca41, I did get the Model 61-F. It was $80, only a short drive, and a good test of my ability to load & transport a welder on my new trailer. It has a new large gauge 50 ft input cord and good condition 45 ft leads, so I basically got the welder for free. It is going to need some work, but I hear that model has excellent arc performance, better than a Thunderbolt or Lincoln AC-225. I will post more as the work progresses.


                • #9
                  Great deal on the 61F! Nice find. Do keep us posted on progress with it.

                  Sorry to hear about the virus, that is just horrible. If the people doing that stuff would expend all that energy on helping instead of hurting people the world would sure be a better place!

                  Sounds like you've put some good thinking into choice of a welder; hope you can find a good Dialarc. What part of the country are you in? Folks here sometimes post when they see what appears to be a deal on a welder, but it's not much help if you're in CA or TX and one shows up in the New England or mid-Atlantic states.


                  • #10
                    Much of the information about the suitability for my needs and reliability of specific models has been through reading past posts on this forum. Good people with good answers. Many professional welders who are willing to help new people, because there is a steep learning curve and correct information can be hard to find. Google will give you 10,000 answers, much of which is wrong.

                    My first search for "stick vs MIG" sent me to a 'spitting match' with no useful information, on one of the other welding forums. Luckily I found this forum where knowledgeable people answer that question with "depends on your application, since no process is best for everything." Craigslist is filled with ads for barely used (usually low-quality) welders because people bought the wrong equipment based on bad advice. I was able to give the 61 F seller some info on 115v welders that corrected the bad advice from a hardware store salesperson and internet posts. Help others when you can...

                    I am in Nova Scotia, which is essentially an island, with a relatively small population. That means it is a long distance to large cities with used equipment for sale. 'Helga's sister' in Maine is 600 miles away. There are welding shops that work on ships and construction equipment, but they are in the industrial parks with 3-phase power. Miller Goldstar 400 for $300 nearby, but it's 3-phase. The used ads are filled with Lincoln 115v MIG, AC-225 Buzz Boxes, and plenty of cheap 'hardware store' 115v junk. Very rare to see the big units like Dialarc or Idealarc.

                    The search continues, thank you for your help.


                    • #11
                      Wow, you live in a beautiful place, but a tough place to be when you're trying to find a good welder. Hope one comes available. Only been to NS once, for a day, all of which was at the Summerside airfield. Back in a former life, I was on a Coast Guard C-130 flight crew taking spare parts to some of our guys who were flying International Ice Patrol out of Summerside. Got to see at least some of the island from the air. Beautiful place!

                      You're a wise man; the number of people who spend $ they can probably never recover on "toy" machines is amazing. Worst thing is people buy them and make absolutely beautiful mig welds that have no penetration, but they don't know that. Can only hope that no one gets hurt.

                      Dont to forget to keep us posted on the 61F.


                      • #12
                        Stefen , I'm a big fan of the Dialarc HF and although after 30 years of use it did just fail me for the first time. Not bad for as much welding as it has seen. As Aero mentioned I did order a New Contactor and hope to have the new part here shortly and get it back up and running soon............

                        But I'm curious with the nature of your business being somewhat outside have you ever considered owning an engine driven welder such as a BobCat? I bought a used one several years ago with just short of 2000 hours that had a recent de-carbon and valve job for under $1k.........Could not be any happier about how many use's that machine provides mounted to my service truck........Arc welding , Yes. power my 211 Mig , Grinding , runs a compressor when needed or lights and just recently kept my neighbor and my Freezer's and refers both powered up for several hours during the day until power was finally restored several days later.


                        • #13
                          Thank you for your input. Unfortunately it is difficult to provide all the relevant information in a short post, leaving people wondering about my choices (and business plan).

                          I am starting a one-person design / build business, and will build one house per year. I will be the designer / supervisor, doing most of the general work, and all of the high-quality finish work myself. If a task requires more than one person, or a certified installer, I will hire day labor and licensed trades-people.

                          I only need one customer per year, in a market that is being ignored by the big developers. (Building small, high-quality, well-designed, energy-efficient, mid-price houses). That should be possible except in the worst recession. I will not become rich, and it is a big risk, but hopefully I will end the constant scramble to find work, and long periods of unemployment that I have in the past, like many people in this region.

                          All equipment will either be at my house, or at one job site, so I do not need the mobility of a service truck for multiple locations. Many contractors and welding shops need engine-drive units and bid the price up, thousands more than a similar size & quality hard-wired unit, so they were crossed off the list very quickly.

                          I used the phrase ‘'my skid-steer’' above so people understood the type of metal I would be welding on, and that I am not going into production making dozens of attachments, which MIG is better suited for. All of the big equipment (skid-steer, mini-excavator) will be rented, I will only own some attachments that are not available to rent. I am careful with equipment I am responsible for. If I did break an attachment I own, I could load it on my truck and take it back to my shop. If I broke the excavator, the rental yard would fix it and bill me for it.

                          I completed training in Oxy / Stick / MIG / TIG in the early 1990’s, literally the same year the economy tanked and jobs disappeared. I have not welded since college, but I remember the basics. I will start my first project next spring, so I have time to study the details again and practice before doing any real welding. If there is any structural steel or very difficult welds in the project, they will be done by a certified welder.

                          Unfortunately college courses do not teach about the selection or maintenance of equipment. They also assume you always have the correct piece of equipment for the task. So I end up asking dumb questions about rectifier diodes; how to test used equipment; and scratch-TIG. (Which is not even discussed in college, never mind taught, even though it is used every day by professional welders).

                          What I equipment need:
                          I am designing the delicate architectural metalwork pieces for gas brazing, eliminating the need for low-amp TIG.

                          I will use a portable stick welder on-site for assembly of architectural metal and other miscellaneous tasks. In the unlikely event I need on-site welding before the wiring is installed, a small generator is cheap to rent for a day. I just picked up a Miller 61-F, 180 amp AC. Supposedly a very smooth arc for a small AC welder. (Hopefully it works, but that’s another thread).

                          I need a 250 amp welder at my house to fabricate a few custom skid-steer attachments out of 1/2 inch thick steel. Plus maintenance on my truck; large architectural metalwork; and the usual miscellaneous stuff. I will not be welding aluminum, so H-F AC is not necessary. H-F DC would be nice, but I can learn how to scratch-start TIG, and brazing is actually a better process for much of the ‘artistic’ work I will do. A basic (non H-F) Dialarc can vary amps while welding with a ‘Hillbilly Remote.’ Hand-crank units (Lincoln Idealarc & Miller Two-Fifty) do not have that ability and would be my second choice.

                          Testing, Reliability & Repair:
                          I know every DC welder has rectifier diodes and other parts that can fail, so they are equal. I have learned how to test diodes on a non-powered unit.

                          Dialarc has an electronic amperage control mechanism which can fail, unlike a hand-crank Idealarc or Two-Fifty. But the Dialarc seems to be reliable, and parts are supposedly around $150. The operational convenience would be worth the possibility of failure.

                          My question is how to test the amperage control before buying the welder? Does it need to be set at all ranges from 10 to 100%, or does the entire control unit work or not? Can I simply test one amperage on high and one on low, or do I need to test across the entire range in both high & low?

                          I know how to test if the High-Frequency is working, but I do not know how reliable and / or maintenance intensive it is and how much it costs to repair.

                          That is a long post and lots of info, but that is how I chose the Dialarc. I hope I explained it well.
                          Thank you again for your input. Stefen
                          Last edited by Stefen7; 08-17-2016, 08:45 AM.


                          • #14
                            Stefen, nice write up with good thinking behind it. Some thoughts in response to your questions. There are no doubt others here with much greater depth of knowledge but here's my two cents worth.

                            The Dialarc controls welding current with a transformer-like device called a magnetic amplifier that is in turn fed by a very simple variable resistor that is essentially like the dimmer in your trucks dash lights; it just controls how much DC current flows through a control winding on the mag amp, which in turn controls the (welding) output current of the amp. The power to run the control circuit comes off the main transformer and through a simple diode bridge rectifier. Mag amps are an absolutely amazing technology perfected by the Germans in WWII, operating on the principles of a device called a saturable reactor. There is a LOT more tech info to it, but that should be enough to understand what's going on in there and give you confidence in the machine. It is just specially desiged coils of wire on a special magnetic iron core. They are essentially like the transformer in your 61F--unless you get a lighting strike, or overheat them dramatically, iron and coils of wire are pretty much bulletproof. So, for testing before you buy, simply test on high and low ranges, using several diameters of rods, and pick a few points on the current adjust knob on each range to see if it welds. Unless the variable resistor has a couple of bad spots, (like if your dash lights go out at some settings of the dimmer when it gets old) there is just nothing besides the control rectifier and the wire to go bad. As long as it welds on various positions of the dial, it's gonna be OK. And, worst case, I can't imagine a new rheostat would be a fortune, and certainly the diode bridge wouldn't.

                            The HF is generated by a spark gap, which is just a couple of finely machined surfaces that need a bit of special care for cleaning and adjustment. No failures there other than misadjustment or improper treatment. The only issue in this area would be the transformer that couples the HF into the output weld current. That could be an issue if it failed; guess is it could be expensive and hard to come by, but I don't know.

                            Remaining are the fan motor, main transformer, thermal cutout switches to prevent overheating, diodes, and switches. Except the main transformer, all these parts are replaceable with generic parts, I would assume.

                            Hope you can find one.
                            Last edited by Aeronca41; 08-16-2016, 09:28 PM.


                            • #15
                              Thank you for the explanation of the Mag Amp. I saw it on the wiring diagram and have not had the time to do any research on it. It makes perfect sense that the 'heavy amp' section is an essentially bulletproof coil of wire; and the 'fragile' part that can fail, carries very little load, so it can be inexpensive and easily replaced. Nice design.

                              In my research I saw several posts where people stated they adapted a foot pedal remote to a Lincoln Idealarc using a potentiometer. But no explanation HOW they did it. That's research I'll have to do if I end up with a hand-crank machine.

                              I actually used the wiring diagram for each model to narrow down my possible choices for used units. 61-F is only slightly more complex than a floor lamp. Miller 250; Two-Fifty; and Lincoln Idealarc hand-crank machines, are very simple but lack remote capability. Dialarc looks reasonable. The Miller 330 (Helga) looks like a plate of spaghetti dropped on the floor. Too complex for me to even think of tackling. My respect to Ryan and all the others who can.

                              Do you know if Miller makes the service manuals available? The operator's manual explains how to gap the H-F points and replace them if necessary, but not how to troubleshoot the system or replace the more complex parts. With a Chilton or Haynes repair manual for my truck, I can work my way through most problems. I'll be OK with the operator manual for the basic unit, but a service manual might be nice in the unlikely event I get a H-F Dialarc.

                              Thanks again. Stefen.