photo of Finished welder with my assistant, Miles

How to Restore a Craftsman Welder

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The Old Buzz Box needs work

photo of A Well-loved 60's-era Craftsman Welder
A Well-loved 60’s-era Craftsman Welder

After learning the basics of welding from my friend Bob, I needed to decide how to restore a Craftsman Welder. I needed practice. Welding concepts are simple, physical skills are hard. Bob anticipated this and offered to send his Dad’s old Craftsman welder home with me. It was generous  — giving me a tool that his dad used a lot, and saving the cost of  a welder before I’ve established my skills. A real jump-start.

It hadn’t been used on decades. One might say it was well-loved, but in need of some work. Also, it’s a simple A/C welder, similar to the old Lincoln buzz box my grandfather had on the farm. Perfectly serviceable, but bare-bones by today’s standards. Nevertheless, I saw possibilities and was thrilled. I wanted to learn welding at its most basic and stick-welding with a buzzbox was it


Single Phase Diode Bridge Rectifier, 300A 1600V 110x67x40mm 4 Terminals Bridge Rectifier
Diode Bridge Rectifier, 300A 1600V
I’ve been looking at welding  videos on YouTube for months now, and there was one upgrade I could make easily. Turning the buzz box welder into a D/C machine. It would involve a big honkin’ rectifier bridge, and some additional connections on the front panel. Also, new cables and a stinger were needed. The insulation on the  old cables was brittle and cracking off and the stinger was worn.

How to restore a Craftsman Welder

photo of welder Interior after cleaning
Interior after cleaning

Cleaning was first to remove decades of funk. I removed the cover to expose — surprisingly little. These welders are simple and consist mainly of a big transformer, switches to select the welding current and — well, that’s about it. I also removed the A/C power switch. It had been bypassed, and I wanted to make sure there were no issues with it. Liberal application of Simple Green  and a scrub brush, followed by a rinse made a big difference. Left in the sun, it was dry in a few minutes.

We can make it better!

Studying the interior wiring, it was clear that the amperage switch selected between two ranges. They allowed welding currents from 25 to 140 amps. Final selection of either the “A” or “B” range was done by plugging the “hot” welding cable into either the “A” or “B” jack. Pretty simple. In theory, the addition of a high-current rectifier bridge would convert the A/C current into D/C. Welding with D/C current was preferred on most on the YouTube videos I had watched. Also, Bob’s welder (that I had just learned to basics on) was set to D/C. Hard to argue with a pro’s choice.

I decided to keep A/C current as a choice and add the D/C capability. This meant I would need to install two sets of new output connections — one pair for A/C and another for D/C. The rectifier would be connected between them. At the same time, I wanted to preserve the amperage switch and “A” and “B” range selection. Putting it all together, I came up with the following diagram.

Craftsman Welder circuit diagram
Craftsman Welder circuit diagram

We’ll need a few parts

This provides the most choices. A/C and D/C either Positive or Negative polarity by simply plugging the welding cables into the correct jacks. Some parts were needed:

Let’s build it!

Parts in hand, it was time for assembly. The 300-amp bridge rectifier was first bolted to the front panel. Because the bridge will generate some heat, I coated the back of the bridge with silicone thermal compound to help transfer heat  to the front panel.

The welding cable connector sockets were next. I made four notched holes in the front panel. The holes are large, and a step drill was really helpful. A small triangular file made the notches, and Voilà — we were done.

photo showing the finished interior wiring
All wired up!

Now the fun part. Connecting all the parts. Normally, this wouldn’t be so bad, but when working with high current, large wire is needed. In this case, #2 AWG stranded copper. About as big as my little finger, it doesn’t bend easily, and tight bends are needed in tight quarters. Also, each jumper has a copper lug swaged on. A hammer lug crimper is really handy for this purpose. The lug is fitted on the cable end and placed into the lug crimper. A stout hammer-blow or two, and the two are as one. Ready to carry some current! Large pliers or even a vise are helpful for making the wire bends.

With the secondary wiring done, a new power cord was needed. The old cord was worn, and didn’t fit the 240-volt outlet in my shop. A new dryer cord did the trick. The final refinement was a furniture dolly to roll the welder around the shop. It’s heavier than a single person can lift easily. Plugged in and turned-on, everything seems right. The fan runs and appropriate voltage is present on the A/C and D/C jacks.

It works.

Lincoln Electric VIKING 2450 Black Welding Helmet with 4C Lens Technology - K3028-3
Lincoln Electric VIKING 2450 Black Welding Helmet
I came back from Omaha with accessories. A new auto-darkening helmet and cotton cap, welding gauntlets, chipping hammer and wire brush. I was even able to get +1.5 optical correction for the helmet. Some scrap from a local metal crafter and a welding table completed the welding suite. Now I just need to practice!

 

11 Replies to “How to Restore a Craftsman Welder”

  1. Hello:

    I have a similar old welder, but mine is the 230 amp model. I’ve been contemplating doing the same kind of conversion to mine, and so I am wondering how yours has held up. Any problems? I noticed you did not add a capacitor or a choke coil to yours – how well does it work without one?

    Regards, Jim

    1. To be honest, I haven’t used it much in the last few months. Busy with other projects. I don’t expect any problems however. With regards to a capacitor and choke coil, the conversions I’ve seen on the ‘net didn’t use one and the people who made the mods reported excellent results. The couple of times I’ve used it with the mods, it’s worked just fine.

      Jim

  2. Good evening,

    I am working to repair and use a welder just like this. It was my grandfathers and has sat for probably 15 years. The cables were all falling apart so I have been working to replace them. I am having difficulty securing the ground back to the adjustable amperage slider on the front. Any suggestions on how to get the cable not to slide out of the piece that it is crimped in to?

    Thanks,
    Matt

    1. That’s definitely a weak part of the original design. The best thing I can think of is to flow solder into the crimped connection. You’ll have to take the slider mechanism apart to avoid damaging the plastic parts with too much heat, and use plenty of flux to help with the solder connection. Since is is already loose, I would make an effort to clean the inside of the copper crimp and outside of the cable so that they’re bright and shiny before soldering. You’ll have to use a stout soldering gun (140 watts or more) or perhaps even a propane torch to get it hot enough. Good luck!

  3. Hi Jim, I’m currently restoring one of these myself and plan to keep it AC only. Would adapting the lenco connectors in place of the old style A/B connectors be any issue at all with it being just AC? Hopefully I’m not overthinking this.

  4. Liked video very much , need better picture of hook up on the bridge rectifier, bit confused. Could you help? Thanks Gary

  5. Wirering in drawing does not correspond to photo of rectifier . Photo shows terminal ac plus going to terminal negative on rectifier, also terminal negative on ac going to positive on rectifier. The two don’t seem right, confused maybe the photo hard to capture the cables correctly. Please verify. Thank you very much. Article is very good.

    1. Gary – On the rectifier shown, the two top terminals are DC current out — minus on the left and plus on the right as pictured. The two bottom terminals are for the AC input. Since the AC is coming from the secondary of a transformer, it is not polarized. The two terminals could be reversed with no change in function. It works fine as shown. I’ve used it to weld many times. I agree it is a little hard to see in the picture though — limited space to position the camera. — Jim

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