What could cause a handful of dead phosphors seemingly overnight? RCA MM36110

[Bard_the_Bowman]

Hello, I've got an RCA MM36110 TV and seemingly overnight it developed a small vertical row of dead phosphors (maybe 1/4" to 3/8"). I've not been displaying anything that would have caused burn-in in that specific spot, at least not that I'm aware of.

Sometimes on startup there is a brief vertical flash in the center of the screen, but it's an inch or two ABOVE these burnt-out phosphors so I doubt that caused it.

I'm assuming at this point that its not fixable, I'm just very curious what might have caused such a thing to happen.

[Josh128]

Hello, I've got an RCA MM36110 TV and seemingly overnight it developed a small vertical row of dead phosphors (maybe 1/4" to 3/8"). I've not been displaying anything that would have caused burn-in in that specific spot, at least not that I'm aware of.

Sometimes on startup there is a brief vertical flash in the center of the screen, but it's an inch or two ABOVE these burnt-out phosphors so I doubt that caused it.

I'm assuming at this point that its not fixable, I'm just very curious what might have caused such a thing to happen.

Theres really no such thing as "dead phosphors". They are simply chemical compounds that glow/emit light when struck by a cathode ray. They can lose luminance gradually over time or quickly if blasted by a high intensity/ non moving cathode ray, but for your CRT to lose some of them overnight can only mean one thing-- they flaked and fell off. When they fall off, it will leave a completely black "speck" or "flake" where they are missing.

One of my "Hitachi Heist" 27MM20B/27MMV30B dual scan CRT sets had a fantastic picture other than a roughly 2mm diameter "black spot" right in the center of the screen. Upon inspecting the tube when powered down, you could see that the phosphors were missing in that spot. They had flaked off. There was literally nothing that could be done to bring them back.

Take a look at your set, powered down, with a bright flashlight in the area in question. you should be able to see if the phosphors have flaked off.

[Bard_the_Bowman]

Hello, I've got an RCA MM36110 TV and seemingly overnight it developed a small vertical row of dead phosphors (maybe 1/4" to 3/8"). I've not been displaying anything that would have caused burn-in in that specific spot, at least not that I'm aware of.

Sometimes on startup there is a brief vertical flash in the center of the screen, but it's an inch or two ABOVE these burnt-out phosphors so I doubt that caused it.

I'm assuming at this point that its not fixable, I'm just very curious what might have caused such a thing to happen.

Theres really no such thing as "dead phosphors". They are simply chemical compounds that glow when struck by a cathode ray. They can lose luminance gradually over time or quickly if hammered or blasted by a non moving cathode ray, but for your CRT to lose some of them overnight can only mean one thing-- they flaked and fell off. When they fall off, it will leave a completely black "speck" or "flake" where they are missing.

Sounds like that might be what happened. I did (lightly) bump into the screen with something I was carrying earlier today.

Here's an image: https://imgur.com/a/VKnfOSA

[Josh128]

Sounds like that might be what happened. I did (lightly) bump into the screen with something I was carrying earlier today.

Here's an image: https://imgur.com/a/VKnfOSA

Yep, 99.999% certain that is what you are looking at. If it was dust or trash that somehow got stuck to the back of the phosphors and was blocking the cathode ray in that spot, it wouldnt be visible on a powered down screen like that. Sorry man, I don't think theres anything you can do to remedy that.

[Bard_the_Bowman]

Sounds like that might be what happened. I did (lightly) bump into the screen with something I was carrying earlier today.

Here's an image: https://imgur.com/a/VKnfOSA

Yep, 99.999% certain that is what you are looking at. If it was dust or trash that somehow got stuck to the back of the phosphors and was blocking the cathode ray in that spot, it wouldnt be visible on a powered down screen like that. Sorry man, I don't think theres anything you can do to remedy that.

Well shoot. Took me years to find this set and I guess it's time to start looking again. Thanks. I really do appreciate the input.