Doug:
While I am not familiar with the Century set up, I have solved this problem before with a Miller transformer that had a screw type adjustment, rather than a lever.
What is happening is that the increased vibration of the secondary winding when under load (welding) is causing the winding to slide on the adjusting guides into or out of the primary winding, increasing or decreasing your settings. On the Miller transformer, there were rails that carried the secondary, with set-screws to adjust the fit to these rails, so that you could increase or decrease the friction needed to move the core and /or prevent the core fom rattling (LOUD buzzing when arc is struck). I would look for something similar inside your transformer (with the power disconnected, of course!) or some method of increasing friction on your lever - secondary movement mechanism, to prevent vibration off setting. (possibly using stronger springs?)
Hope this helps, but perhaps Brande might be able to be more specific!
As far as the Miller goes...
There were wooden shims available from the factory to take up the"slop" and vibration.
The Century (aka known as Solar, Powermate, and other designations) had a locking lever on the amp adjustment. This arrangement did not work as well as promised.
Anyway-both of these units are "sliding core" type transformers.
Keep this in mind. If you want steady settings, you must find a way to to keep the cores from sliding. Bungee cords, shims, rope, and other methods have worked from time to time.
Hope this helps a little, if not...contact me directly.
Good Luck
brande
Thanks for the replies. On my set up the sliding cores are riveted onto the handle that you use to slide it up and down to the desired settings. There are two rivets on each slide, they are loose, I was wondering if they are suppose to be loose like that. Also when mine is set the sliding cores are not even, in other words one side ends up higher than the other, could this make it move on me when welding (this is probably due to the loose rivets). I have pushed them down by hand to even them off and it still moves when welding.I hesitate fiddling around with the rivets unless I am sure this will fix the problem. Regarding the wooden shims, would they be hard to make and where exactly do they go. I may have to go with the bungee cords, but it would be nice to get it working like it is suppose to, I am prepared to fiddle with it first.
On my old Linde, you have to turn the lever to loosen it up. After you make a change, you then screw it down. Perhaps you can modify yours.