What is the best way to clean a 40 year old tube without removing the markings stamped on it? I've used various cleaners on cheap tubes but I have a few large 7971's that I want to clean and leave the markings unharmed.
Don't get anything wet anywhere near the print. Many tube companies used water soluble paint, and Burroughs tubes do not have particularly resilient paint. When I clean a tube, I use a lightly damp cloth (water only) on the bulk of the tube, and I do not touch the print at all. If you need to clean near the print, use something delicate and precise to do the cleaning so you do not actually touch the print. We treat the print on all tubes as no-touchy.
A little-known fact, Burroughs had such a problem with the print rubbing off their beam switching tubes inside the box that later beam switching tube boxes have very tiny protruding nubs in the styrofoam insert, which hold the surface of the tube away from the foam by a fraction of a millimeter.
I think I'm going to take everyone's advice here. I had some luck using a microfiber cloth and avoiding the markings altogether. I read a few suggestions on The Google where people had luck with Windex and CLR but I don't really want to try this method.
Regarding the orange coating - I know that warm water will remove that film :-/ Maybe an ultrasonic cleaner would work...but not many people have one sitting around.
The red paint isn't exactly water soluble, but it will definitely peel off in chunks under warm water. I think if you're very gentle and avoid the yellow print, you should be able to clean it with a moist cloth. Don't apply too much pressure, use cold water, and don't use so much water in the cloth that it leaves standing beads on the tube. Isopropyl alcohol may also work, and evaporates faster than water. If the dirt requires CLR to remove, I'd just as soon leave the tube dirty.
I think an ultrasonic cleaner would completely destroy the print and possibly even break internal spot welds, but if somebody wants to donate the tube, I can drop it in my cleaner and see what happens.