[MRX37]

Originally Posted by julianburke

Whoa! Whoa! Whoa! I often see misinformation in this group and this is one of them! Here in Knoxville there was a picture tube rebuilding plant of which I worked when I was in high school. I know every facit of tube rebuilding so let me set this straight of what's been said so far.

First, when a tube has gone to air you CANNOT "reseal" a tube and reuse the old gun mount as the cathode has returned to its' original form and will not work again. Once a tube has gone to air it now contains moisture which will attack the phospor if left there. Tube would also be so full of impurities from the tainted gun mount that it would not work anyway.

All of your theories of how they let the air in without damaging the tube are all wrong. After the tube is washed and cleaned and all of the old dag is removed with steel wool it is set into a rack gun side down. There are no dremel tools ever used in the process. (where would anyone get this idea? You scratch the glass on any surface of a live tube and you risk implosion and injury) Here you need a clean cut and a dremel tool cannot do it anyway. I have seen dumbasses scratch tubes before and the outcome is not good. When we inspected tubes for rebuilding, we look for scratches esp on the faceplate and they were REJECTED. At this point there are a pair of tongs with a nichrome wire that is squeezed around the base of the neck where the break is desired, wrapping the wire around the neck. About 12 volts at 10 amps, the wire gets red hot and about 8 seconds later it is removed and I would wet my finger lightly and touch the heated area and it would go "chink" with a perfect break completely around the neck where heated. We would then wrap a plastic bag and tape it to the neck which had a hose attached to it from a nitrogen tank. This kept moisture out of it. The vacuum seeps down slowly and no damage to the faceplate. When vacuum is finally down, you pull the gun assembly out completely intact. Now it's ready for the next step and this entails installing a new gun mount along with a glass lathe.

If a tube has been down to air for a period of time and the break was around the gun mount, it can be rebuilt but depending on the moisture content of the air inside the tube will most likely cause "staining" of the phosphor on the faceplate.

By the way-one more important thing: DON'T EVER *REPEAT* DON'T EVER REMOVE A PRESSURE BAND ON A LIVE TUBE!!! It will implode. I saw a dumbass TV repairman do this to make it fit into a set one time and he found out the hard way!


Summary:

*You don't just put a new cathode in an old gun mount. This is impossible unless you build gun mounts and it's not feasable anyway.
*When a tube is cracked via the hot tongs, you don't put any tape on the break.
*You cannot put a new stem on any gun mount (new or used) and evacuate the tube because the cross fires would damage the pins or wires coming out of the button of the gun mount. The pins or wires were annealed to that button and heating them will ruin that annealing process and cause a leak if not crack the button. New stems come with new gun mounts and you cannot weld on a new stem if broken. If broken, you throw the gun mount away.
*You cannot replace the phospors on a color tube. Again, this is a new manufacturing process and if you could do this, you wouldn't be playing with used tubes.

Any more questions for an expert?

Sounds like you know your stuff. Thanks for the info.