Does leaving a CRT on without a signal cause any damage?

[BillyHW]

Just curious. Does leaving a CRT on without a signal cause any damage? I'm not talking about static. Just the black "glow-ey" screen you get from the composite video jack if your box/system is turned off, for example.

 

(And while I'm here, I guess I can ask if static causes any damage.)

 

Merci.

[atarian63]

We sold alot of CRT composite and vgas monitors back in the day (thousands and thousands) manufacturers always said to turn them off, I never saw any screen issues from being left on with no signal however have seen them die from excessive time on, everything has a certain MTBF. Magnavox composites were known to not come back on if you shut them off after being on for a long time, but those were not well constructed and had thin boards. not uncommon to see a flyback come loose in shipping.. anyway I personally always turned mine off but either way you should be good.

 

Static like on the face of the tube is generally cleared on most newer crt monitors at power on, they have a degaussing ring around the front of the tub, the degausses with each startup. does not always remove all static but that is really not it's purpose.

Edited January 16, 2014 by atarian63

[Osgeld]

unless you physically see the tube shut off like in a more modern computer monitor it is running the screen. Now a blank screen is not wearing out your phosphors or burning anything into them, but the power supply and the scan gear is still running full tilt and at high voltage.

 

so while I wouldnt turn it off for a break or something, I wouldnt make a habit of leaving it on all night or something

[BillyHW]

We sold alot of CRT composite and vgas monitors back in the day (thousands and thousands) manufacturers always said to turn them off, I never saw any screen issues from being left on with no signal however have seen them die from excessive time on, everything has a certain MTBF. Magnavox composites were known to not come back on if you shut them off after being on for a long time, but those were not well constructed and had thin boards. not uncommon to see a flyback come loose in shipping.. anyway I personally always turned mine off but either way you should be good.

 

Static like on the face of the tube is generally cleared on most newer crt monitors at power on, they have a degaussing ring around the front of the tub, the degausses with each startup. does not always remove all static but that is really not it's purpose.

 

I mean static in the sense of noise. Like you'd get on a TV channel that has no broadcast.

[+save2600]

No.

[AussieChris]

Hello,

 

In my opinion, it will still " wear " the tube. By this I mean the heater will age, and as you wind up the brightness to compensate the display will get blurry. And on a different note, an LCD can also get " burn in " Many people are not aware of this either.

 

Regards Chris

[Osgeld]

yea I did it to my 5 inch LCD I use on my apple II, it eventually went away but a good solid day with ADT on the screen left a nice giant ghost on the LCD for many months

[BillyHW]

yea I did it to my 5 inch LCD I use on my apple II, it eventually went away but a good solid day with ADT on the screen left a nice giant ghost on the LCD for many months

 

Next time run the flurry screensaver on Mac OS X for a few hours. Worked like a charm for me. Felt like I had a brand new monitor too.

[Osgeld]

yea cause a 1984 8 bit apple II with 128k runs osx so well

[Kyle22]

Hello,

 

In my opinion, it will still " wear " the tube. By this I mean the heater will age, and as you wind up the brightness to compensate the display will get blurry. And on a different note, an LCD can also get " burn in " Many people are not aware of this either.

 

Regards Chris

The heater may age very slowly, but the cathode (what the heater heats) will not give up electrons very quickly if there is no anode current. I have seen TeleVideo terminals run 15 years non-stop with a bouncing box type screensaver. There is a small current in that case, because there is something on the screen.

 

A completely blank screen shouldn't draw any amount of current (electrons) from the cathode.

 

There are two schools of thinking on this one. Some old TVs had an "instant on" feature which kept all the tubes heaters energized at half power so they would warm up faster, this also eliminated the "thermal shock" of going from cold to hot every time the TV was turned on. In theory, it made the tubes last longer.

 

Others disagree with this theory.

 

I have had both types of TV, and I really can't say which ones lasted longer. I had (in the 90's) a 1964 RCA NewVistaColor that was excellent. The NuVistor tuner was amazing, it would pick up channels from far away. The Nuvistor is a small vacuum tube in a metal can that is slightly larger than a pencil eraser. http://en.wikipedia.org/wiki/Nuvistor

 

I don't remember if it was the instant on kind, or not, but It worked beautifully for years. Yes, I left it on for days at a time.

 

I think a lot of it simply boils down to quality of manufacture.

[Keatah]

Hello,

 

In my opinion, it will still " wear " the tube. By this I mean the heater will age, and as you wind up the brightness to compensate the display will get blurry. And on a different note, an LCD can also get " burn in " Many people are not aware of this either.

 

Regards Chris

 

Hello,

 

In my opinion, it will still " wear " the tube. By this I mean the heater will age, and as you wind up the brightness to compensate the display will get blurry. And on a different note, an LCD can also get " burn in " Many people are not aware of this either.

 

Regards Chris

There would be a slight "burn-in" over a long period of time, really hard to notice because it's an evenly distributed glow across the whole screen. This would manifest itself a subtle loss of contrast. I don't recall anyone complaining about it.

 

Yes, LCD can get burn in. The crystals squish the fluid out and can get stuck in position by Van der Waals force. Think surface tension and meniscus, but electrostatic in nature.

 

You can make your own refresher that cycles through the following colors:

Black, white, 25%gray, 50%gray, 75%gray, red, green, blue, cyan, magenta, yellow, and repeat. This twists all the triads through their full range and allows for the fluid to evenly redistribute. It also allows the crystal to re-stack itself evenly; think combing your hair prior to styling. With the crystal stack more orderly, light is transmitted through the panel slightly more vibrantly.

 

Some Dell LCD monitors have this color sequence built-in. It runs when there is LOS. I don't believe it has the 25-50-75 grays though.

 

 

 

Next time run the flurry screensaver on Mac OS X for a few hours. Worked like a charm for me. Felt like I had a brand new monitor too.

 

yea cause a 1984 8 bit apple II with 128k runs osx so well

 

OMFG.. more useless prattle. You'd hook the "failing" monitor to a system that can run flurry (or similar).

[AussieChris]

Hello,

 

I can see everyone's point of view, but many components will only work for a certain number of hours. Caps in the deflection circuit for example. In the good old days, a Japanese TV would last 20 years or so. Many Chinese TV's would be lucky to get 5 years. I don't want to start an arguement about this, as it is my opinion only. I used to replace Caps in the deflection circuit 20 years ago in a large computer companies monitors. There was also a " grey scale " monitor that had a tube life of around 12 months. ( burn in was bad )

 

You do what you feel is right, and everyone else can do what they want. I remember many years ago on a mainframe site it would be powered off over Christmas, on power up there were always many Disk's and fans that would fail. Leaving them on caused less problems. Even Caps in the start circuit for Disk drives would stop them starting. The thermal issues from start / stop are the main reason not to power off IMO.

 

A CRT without sleep mode I would power off when not in use, as with the high voltage inside and with the chance of water leaking in there is a fire risk. ( from a roof leak ) Why is it that when water leaks into an appliance that would be fine when dried, people always turn it when it is wet to " see if it works "

 

Regards Chris