Restoring a RCA 21CT55

[Electronic M]

Originally Posted by etype2

It looks like a hole opening up. If I could get a macro on it, we’d see more. I will keep my eyes on it to see if it changes in appearance.

A hole opening up in what?

Unless that is the point the beams light up for a moment after power down it should never change*.
*Unless there is some abrasive debris between the phosphor and shadow mask and you set the tube face down and shake it.

[SwizzyMan]

Likely its been there the whole time and you are just now noticing it. Phosphor just doesnt fall off the screen. The conditions inside the tube have been the same for over 60 years. The only real way it will get bigger is if the tube is under heavy vibration or shock.

It's nothing to worry about.

[etype2]

Originally Posted by SwizzyMan

Likely its been there the whole time and you are just now noticing it. Phosphor just doesnt fall off the screen. The conditions inside the tube have been the same for over 60 years. The only real way it will get bigger is if the tube is under heavy vibration or shock.

It's nothing to worry about.

I believe your right.

[etype2]

Originally Posted by Electronic M

A hole opening up in what?

Unless that is the point the beams light up for a moment after power down it should never change*.
*Unless there is some abrasive debris between the phosphor and shadow mask and you set the tube face down and shake it.

Like a new tile job with pinholes of collapsed grout. Likely been there, just never noticed it.