Author Topic: CRT TVs glowing when off  (Read 1379 times)
Cole D.
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CRT TVs glowing when off « on: October 27, 2018, 03:56:03 PM » Author: Cole D.
Has anyone noticed this before? We have CRT tube TVs in my room plus my parents room, and I noticed after I turn the lights off sometimes the screen has a glow. It does it even if they haven't had the TV on. It kind of reminds me of how fluorescent lights and CFLs have a phosphor glow for a few seconds after turning them off. So I guess the light causes some reaction with something in the CRT. I haven't seen this with LCD or LED TVs that we have.
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Re: CRT TVs glowing when off « Reply #1 on: October 27, 2018, 10:51:02 PM » Author: Medved
This is normal behavior of the screen phosphor, it get excited by rhe ambient light. Most phosphors do that in some extend.
With CRT the phosphor is directly on the screen, so quite exposed.(the front glass uses to be darkened (to improve contrast against reflections, picture has to pass once, but the reflection twice), but still passes more than half of the light.

The LCD panel itself has no phosphor at all, it just regulates how much of the backlight passes through.
The only rhing with phosphor is the backlight (either tube or LED stripes), so for the afterglow to be visible the ambient light has to first pass through the panel, then excite the phosphor, the phosphor afterglow then has to pass through the panel back to become visible. As the panel itself passes just about 10% of the light even when displaying white and few orders of magnitude less when dark (off; see the rated screen contrast) and the light has to pass twice through it, there is no chance the afterglow to be any visible at all, even when the lamp phosphor would be very strong glowInDark...

And OLEDs do not have phosphors at all, there the subpixels are LED junctions directly of the required color.
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ace100w120v
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Re: CRT TVs glowing when off « Reply #2 on: October 28, 2018, 01:56:41 AM » Author: ace100w120v
I've seen this too!
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Re: CRT TVs glowing when off « Reply #3 on: October 28, 2018, 02:11:11 PM » Author: Medved
I remember as a kid I was "drawing" ghosts on the screen using a small flashlight, to scare my younger brother at the evening...
It was on a BW TV, there the effect is stronger...
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Re: CRT TVs glowing when off « Reply #4 on: October 28, 2018, 04:04:27 PM » Author: FGS
Camera flashes set them off too. An odd way to find that missing 5.5 portable TV. Just take a pic of the area with the flash and look for the glow. Cheesy
« Last Edit: October 29, 2018, 07:44:39 AM by FGS » Logged

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Re: CRT TVs glowing when off « Reply #5 on: October 28, 2018, 10:50:09 PM » Author: tolivac
Remember the really old BW sets-A Hoffman that was in the basement-this was "our" sets used by us kids-this was back in the fifties.Mom and dad used the brand new table model Zenith in the metal cabinet.Both of these would give a glowing dot in the center of the screen after being turned off-the HV in the crt circuit bleeding off.The Hoffman had green phosphors in its pix tube.The Zenith was true BW or monochrome.Surprized our eyes didn't get rotted watching that green Hoffman.Remember Micky Mouse,Sky King.Sea Hunt,Howdy Doody,Rooty Kazootie,Winky Dinks, and many others from that old TV!Have some of these on DVD-they look so much better on a modern flatscreen set!
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Lightingguy1994
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Re: CRT TVs glowing when off « Reply #6 on: November 23, 2018, 10:06:30 PM » Author: Lightingguy1994
I noticed this as well. I have a violet laster pointer and when i shine that on a crt it make it glow very brightly and can draw long lasting things on the screen. Upon closer examination
i see that it is only the green phosphors in a colour set that respond. The red and blue do not so the dot is always greenish blue (blue from the lasers colour + green from stripes) I can make the entire face of the crt glow brightly if i set the laser lens to 'wash' making the beam more like a flashlight
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Re: CRT TVs glowing when off « Reply #7 on: December 02, 2018, 03:58:42 AM » Author: mefurd98
I've seen that before! It always scared me as a kid!
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Re: CRT TVs glowing when off « Reply #8 on: February 04, 2019, 06:57:15 PM » Author: icefoglights
Remember the really old BW sets-A Hoffman that was in the basement-this was "our" sets used by us kids-this was back in the fifties.Mom and dad used the brand new table model Zenith in the metal cabinet.Both of these would give a glowing dot in the center of the screen after being turned off-the HV in the crt circuit bleeding off.The Hoffman had green phosphors in its pix tube.The Zenith was true BW or monochrome.Surprized our eyes didn't get rotted watching that green Hoffman.Remember Micky Mouse,Sky King.Sea Hunt,Howdy Doody,Rooty Kazootie,Winky Dinks, and many others from that old TV!Have some of these on DVD-they look so much better on a modern flatscreen set!

Green screen TVs?  I didn't know they made them.  I grew up using green screen computer monitors.

My parents had a small portable black and white TV.  I remember if I turned it on than off, I could get a really bright and persistent dot in the middle of the screen.
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Cole D.
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Re: CRT TVs glowing when off « Reply #9 on: February 09, 2019, 04:21:25 PM » Author: Cole D.
I noticed my TV glowing again this week when the light was on in room. I turned TV on and then off in dark, and I could tell the four corners had white light and the center had a white going up and down for about 40 seconds after I turned it off.
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Re: CRT TVs glowing when off « Reply #10 on: February 09, 2019, 06:04:25 PM » Author: Ash
Flashes after the TV is switched off can be caused by electrical discharge in the CRT itself - as i understand it, negative charges trapped on the Glass inside surface escaping towards the edges of the screen, where there is a metallized layer
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