10BP4 - bubbles in glass

[bandersen]

I took a chance and picked up an untested CRT on eBay. It turned out to be a 10BP4 removed from an RCA 721TS. Too bad the set didn't come with the tube.




At first, it tested very weak.


After about two hours right in the middle.


After using the "rejuvinate" function, it read a little better. I popped it into an Admiral 24A12. I need to adjust the ion trap and centering a bit, but otherwise it's working fine.
That means I have a good CRT for my GE 802


Something I noticed in both this 10BP4 and the old GE 10FP4 is a lot of bubbles in the face. So do some of my 7JP4s. The newer CRTs I have of those types don't have any bubbles. I wonder if these defects were common in early tubes ? They are somewhat visible if you sit cloes and know where to look. I suppose they're the equivalent of a dead LCD pixel today.