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I have a 10BP4 out of a Zenith that is totally worn out. The face has brownish blotches across it-I can only guess these are ion burns. I was able to get a raster after heavy rejuvination but it didn't hold.
I have a Sel-Son test crt, the type that is in a seperate box and connects with extensions cables. Sets that don't use yoke plugs need jumper wires to make the connection. Once while working on such a set I didn't have the connections tight enough so the test yoke saw no voltage. For a second (until I hit the power) the raster was concentrated in one point in the middle, and glowed orange. There is now a hole in the phosphor; crt still works fine.
My mother bought an RCA console from a freight salvage in the mid-90s. One corner had an obvious ripple in the shadow mask. I never heard her complain about it, though it always bothered me. I can't remember if I ever tried to degauss it out of there, but I don't think it would have helped.
I have noticed, mostly on DuMont built picture tubes, that the finish on the glass face will have imperfections. It is not uncommon on older color crt's to see bad phosphor dots with either a color missing or maybe a red dot where a green one should be, etc. GE seemed to be good for this.
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Bryan
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