I bought a General Radio 20Amp Variac at a yard sale for a buck :D. It's an impressive piece of fifties technology; weighs twenty pounds and looks exactly like what Igor grabs onto when Dr. Frankenstein shrieks "More voltage! More voltage!"

But it's been pinned at one value for a long time. How long I don't know, but probably 30-40 years. I removed the screw the previous owner used to pin the dial, which should have freed it up, but the plate that carries the brushes is stiff and can only be rotated by tapping it lightly with a mallet.

I suspect the problem is hardened grease. Does anyone know how to dismantle the variac for cleaning, or a site where instructions can be found? I got the cover off it but beyond that we're talking about undoing circlips without any idea of what's beneath them and generally pounding on things in the hope they'll move, a practice otherwise known as Invoking the God of Things That Go Ping!

Man,

The whole "Mallet, and Pounding" thing seems kind of scary to me. Finesse, unless it's flat out welded together.

Good luck,

Ron

Try some penetrating oil and let it soak for DAYS....
Wd-40 is a witches brew of solvents that could be tried
WITH NO POWER APPLIED till the thing has been setting for days...
Carb cleaner (spray type) is also a nasty mix
Something that old shouldn't have modern sensitive plastics in it...
When trying to move it don't force, go back to the other way till it
stops again, like rocking a car out of the snow.

Either it's petrified grease or rust. Let the solvents do the work,
I've ruined stuff before thinking brute force could overcome a
tight fit and petrified grease. SNAPPPPPPPPP :cry:

There have been things that an wrench extender bar and BIG vise couldn't move but the repeated impacts of an impact adapter on a plain jane electric drill made short work of... while I was holding the thing in my hand!!!
I learned a lesson there.

Good Luck :thmbsp:

The shaft is a composite of aluminum and fiber, careful you don't bend it, the disk on the rear with the brush can be removed, should have 2 allen set screws to remove it, you can then remove the whole shaft. Just remember the order that the bushings and spacers go in – or should I say fall out.

WD-40 and lots of patience fix mos problems. Besides, those variacs were meant to survive a nuclear blast.

The shaft is a composite of aluminum and fiber, careful you don't bend it, the disk on the rear with the brush can be removed, should have 2 allen set screws to remove it, you can then remove the whole shaft. Just remember the order that the bushings and spacers go in – or should I say fall out.

What he said.. :yes: