I have an interesting question about burn-in...

Are there certain types of tubes that are more susceptible to burnin than others? How do they make "burn resistant" CRTs?

For instance, there's an ancient CRT surveillance monitor with the 4-up display (4 squares on 1 screen) at a local Illwill, and it's been there for YEARS. Recently i saw it with the power off, and there weren't any burns. Once, over a long weekend the computer restarted unattended and was at the BIOS screen (I have a password) for lord knows how long... and there weren't any burns on my Trinitron.

Yet, there are some displays at the bank which run a slideshow and they have a horrendous BSOD burn on them....

How long do you think it would take one of those tiny viewfinder, old roundie colour or BW tubes to burn?

Probably cheaper made CRT's will burn in quicker. I guess it's all dependant on how the phosphor coating is formulated.

The biggest risk factor for burn-in (other than length of time a fixed image is displayed) is the contrast setting. Keep the contrast low enough, and you may never get a burn.

Color CRTs have seemed more burn-resistant than B&W ones in general to me.

High-persistence phosphor crt's used in pc monitors are LESS susceptible, because, well, they have to be. Not sure how they would avoid burn-in with a standard display though.

Several years ago, a local store had two 20-inch televisions (RCA and JVC) hooked up to the camcorders on display. Unfortunately, most of the camcorders never had their demo mode turned off and ultimately showed the feed to the monitors. When the store got rid of the display, they had tried to sell the demo televisions with the burn-in, obviously, no one bit.

The tiny viewfinder in older camcorders, from personal experience, took about two weeks of constant use (time stamp graphics) to notice burn in.

Phosphor burn-in susceptibility depends on both the composition and the physical processing of the phosphor. It doesn't necessarily depend on how cheap it was, but maybe on whether burn resistance was traded for other desirable characteristics.

One project I worked on used a flying spot tube. The first tubes we had could be ruined if the vertical sweep collapsed. Later on, we got some samples from Tektronix using some sort of thin film phosphor. They had studied the problem extensively due to the likelihood of burning oscilloscope tubes. Probably every tube in every scope ever put into service had a burn spot somewhere. This new Tek tube could sit with the vertical sweep collapsed for an extended time, and it would creat the barest shadow in the picture when sweep was restored.

For any given phosphor formulation, the amount of burn seems to be proportional to total charge absorbed, so turning down the drive definitely helps.

Very interesting answers :)

I thought that the phosphors in a TV CRT were the same as a computer monitor, just a finer dot pitch or something

NOw i know better :D

I used to see a lot of burn in back when monochrome computer monitors and text based systems were still common. Often the burn would be sharp enough to read the text that had burnt in, usually a login prompt or menu. I've seen monochrome plasma displays with screen burn. Most text based systems have no provision for any kind of screensaver.

Most of the burnt in color monitors I've seen have been embedded displays in gaming machines, ATMs or connected to PCs that are basically unattended (server consoles, etc). A color CRT usually doens't spend enough time on the average users desk to burn in.

I've got a couple of 20 year old Trinitron video monitors that have time code numbers burnt in. They still produce a bright picture with good focus, the burn in isn't really noticable unless you specifically look for it.

On the other hand the other day I say a recent Sony WEGA flat CRT with severe burn in and almost no green. It had only lasted a couple of years as a surveilance monitor. The burn was so sharp you could make out the layout of the store in the shadows on the blue screen.

Screen burn used to be a good thing for those of us who had no money back in the day. I used a burnt 17" PC monitor for a while that cost me $40 when a similar monitors usually sold for $300+. A friend bought a screenburnt 21" TV for $25 when similar sets sold for $200.

Burn in is mainly an issue for projection TVs. I've never seen a direct view TV with burn in from normal use. Even channel logos and video games aren't a problem as long as its use is varied. Just don't leave CNN on your vintage TV for 5 years straight and it will be fine.

Dr.ido, about those WEGA sets and burn-in, I suspect the scan-velocity modulation can be part of the problem since it often results in a pseudo-ultra-sharp image. Yet another reason to disable it. I have a Sony wega and I did some mod where I cut the svm wire. Don't recall where I saw the tutorial, think it was the sony forum. Anyway, svm plus the skyhigh factory contrast setting on these sony's and you have a recipe for severe phosphor burn, especially as a heavily used monitor.

And come to think of it, a LOT of b&w sets I've seen, vintage or not, have some type of burnt screen. On vintage sets its either the center dot due to lack of a spot-killer, or the infamous vertical collapse burn across the screen.

Dr.ido, about those WEGA sets and burn-in, I suspect the scan-velocity modulation can be part of the problem since it often results in a pseudo-ultra-sharp image. Yet another reason to disable it. I have a Sony wega and I did some mod where I cut the svm wire. Don't recall where I saw the tutorial, think it was the sony forum. Anyway, svm plus the skyhigh factory contrast setting on these sony's and you have a recipe for severe phosphor burn, especially as a heavily used monitor.

And come to think of it, a LOT of b&w sets I've seen, vintage or not, have some type of burnt screen. On vintage sets its either the center dot due to lack of a spot-killer, or the infamous vertical collapse burn across the screen.
You can also disable SVM in the service menu

Duane, according to the FAQ the svm isn't totally turned down when you set it to off... Every model is different I guess, though.

I once saw a picture tube that I KNEW came from a Pacman arcade cabinet. It was just the tube itself, but I could see the outlines of Pacman's maze burned into it clear as day.