Problem with AC stick welder

[MillWeld]

I have a 40 year old SD Lee ac buzzbox which has served me well until yesterday. The locking lever will not hold the current constant at high amps, say ~200amps. This unit has a sliding encapsulated iron core that slides between the primay and secondary coils to give the selected current. I have taken the cover off for access and (with power unplugged) I cannot budge the sliding iron core by considerable hand-applied force, yet when welding it slowly moves giving progressively lower current unrill I lose my arc. (I'm using 5/16" E7018 electrode) I'm amazed at the apparent attractive force it must generate.

I'm in the market for another welder but need input from welders in the form of comments and/or suggestions for possibly repairing it.

Thanks,
Bob

 

[SPYDERLK]

Is there a way you can augment the force applied by the locking lever?

 

[MillWeld]

There are a couple of cams and rollers between which I could insert a shim(s), I suppose. Maybe I'll try that. If it works, at least I can finish my current job befoe I decide on another welder.
Thanks,
Bob

 

[rankrank1]

Seems that troublesome locking lever is the downfall of that Century brand welder (also rebranded under many house names). While I see no reason that the original design should not be repairable with some ingeniuity applied it seems too many people simply give up and toss an otherwise working welder.

If it were me: I would first try to fabricate my own repair to make existing design work. If that did not work, I would investigate buying parts from Lincoln (Lincoln purchased Century a few years back). Of course, I would not spend much money on parts as you likely have a $75 welder in value. Replacement parts may not even be available anyway as Lincoln obsoleted many Century parts.

At this point if nothing bears fruit it is time to think outside the box with a cheap backyard new design to operate that lever as well as hold it in place:
a) Option #1: Carefully mount a salvaged car scissor jack (maybe $5 from a junkyard) on an angled shelf attached the front of the welder. Then use the jack crank to adjust the lever. This system if done right will eliminate the need for the locking lever altogether and likely even give more detailed amp adjusting capability than the original lock did.
b) Option #2: Sorta could do the same thing with a threaded rod adjust system with a plate mounted to the top of the welder. (Note: the thread rod system will allow more for angle changes on that adjuster lever if staying parrallel to fixed plates is not possible. Slots instead of holes can be incorporated into the fixed plate and into the extension on the adjuster lever to allow for angle changes

I will try to add crude concept sketches:

 

[CNC Dan]

thats a few good ideas.

I might just atach a metal bar to the front of the welder and use a pair of vice grips to clamp the lever in place.

 

[rankrank1]

thats a few good ideas.

I might just atach a metal bar to the front of the welder and use a pair of vice grips to clamp the lever in place.

I thought of that one too, and I agree it would be extremely easy to fab up, but I would not personally like that set-up because it requires 2 hands to operate it. I like being able to adjust my amps up or down a smidge easily with one hand while still in welding gloves.

Flip my hood up, adjust the welder with my one free one hand, keep the stinger in my other hand, flip my hood down and return to welding.

 

[Shield Arc]

I would not personally like that set-up because it requires 2 hands to operate it. I like being able to adjust my amps up or down a smidge easily with one hand while still in welding gloves.

Flip my hood up, adjust the welder with my one free one hand, keep the stinger in my other hand, flip my hood down and return to welding.

You know what you need? A machine that has a remote, you can adjust the machine as you're welding.

 

[MillWeld]

I got my welder working again, albeit, rather crudely thanks to some comments. 1) the reason the moveable iron core would not stay locked in place was that the locking cam has ruts worn it from many years of the roller riding on it. It just could not maintain the force necessary to keep it fixed in place. Adjustment of a locking nut was all that was necessary to compensate for the wear. 2) the iron core still moves with much difficulty due to worn linkage, however, if I apply force via hand directly to the center of the iron core assembly it moves readily because there is no side component to the hand-applied force. To solve this problem [temporarily] I drilled a hole on the top of the chassis and, using a fiberglass rod, I can push the assembly down quite easily and get the amps where I want it.
At least I have a working welder and can finish the current job until I decide on a permanent solution.

Thanks again,
Bob

 

[rankrank1]

You know what you need? A machine that has a remote, you can adjust the machine as you're welding.

Yeah those look to be just the ticket for a pro level welder, but quite pricey for a backyard hobbyist like me using only a low cost Miller Thunderbolt (buzzbox). Actually, My buzzbox is never more than a few feet away from me. All the manufactures pretty much universally recommend extending the supply power input cable over using longer than standard welding lead lengths on the buzzbox class of welding machines. Hence, I always run stock welding lead lengths and use an extension cord to move the welder close to where I will be welding.

It is No problem to take a step or two away and turn the crank on the welder as long as the adjuster easily operates with only one hand. That said, I do not want it to have to operate with more than one hand as I do not want to have to bother with trying to find a spot to lay the stinger down (especially in damp grass).

The OP AC buzzbox is not really worth much in the way of money ($75-$100 or so max), but it is certainly worth fabbing up something low cost from the scrap pile that solves the issue and actually makes the welder functionally better than it was originally in this case. (I always hated those Century adjuster slide mechanisms even when they were brand new - let alone well worn).

 

[rankrank1]

...the iron core still moves with much difficulty due to worn linkage, however, if I apply force via hand directly to the center of the iron core assembly it moves readily because there is no side component to the hand-applied force. To solve this problem [temporarily] I drilled a hole on the top of the chassis and, using a fiberglass rod, I can push the assembly down quite easily and get the amps where I want it....

Maybe you can do away with all that worn linkage altogether by removing it and adapting the threaded rod idea that I posted earlier directly to the core itself instead of the existing linkage like my concept pictured. (Look on Miller's site at the older generation thunderbolts that had top crank for the amp adjuster. Those manuals are available for free viewing and do contain pictures as well. Newer generation Thunderbolts have the crank on the front instead of the top).