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Question CRT TV

KeepItSimpleStupid

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The electron gun has a finite life because of the filament. The less brightness, the more life. That's what kills the tube most of the time.
Mechanical shock is another. Don;t get mad and throw a pair of scissors at it. My father replaced the tube when someone did that. That image of the struck tube is still in my head.
 

AnalogKid

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Most Helpful Member
Another factor is thermal cycles. Do not turn on the TV for just a few minutes. The electron gun elements are very close together, with hundreds of volts across very small gaps. Everything moves around as the tube warms up and cools down, and inter-element shorts are common in old tubes. You can delay the onset of this potential problem by limiting the number of thermal cycles.

ak
 
If I reduce the brightness of the CRT TV, will the tube have a very long life? some people say that this is a myth and the only solution is to decrease the voltage of the filament using a resistor but I have little experience to perform this procedure
 

Nigel Goodwin

Super Moderator
Most Helpful Member
The electron gun has a finite life because of the filament. The less brightness, the more life. That's what kills the tube most of the time.
Mechanical shock is another. Don;t get mad and throw a pair of scissors at it. My father replaced the tube when someone did that. That image of the struck tube is still in my head.
To be fair, smashed CRT's via thrown objects were EXTREMELY rare - as the front of a CRT was hugely strong, for that very reason.

However, with flat screen sets (Plasma or LCD) it's quite common, as they are fragile and easily smashed - and countless ones were smashed by WII controllers :D

Best (worst?) I've seen was a Sharp LCD we wall mounted in a pub - and you could plainly see the multiple pool cue marks on the screen where someone deliberately smashed it.
 

AnalogKid

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Most Helpful Member
Technically, you want to reduce the contrast. In a well-designed TV, the brightness control sets the brightness of the black parts of the image. You turn this up in a well-lit room to be able to see subtle differences in things like shadows. But in a darkened room, that same setting will make all of the dark image areas look grey, so you turn the brightness down so the dark areas are dark again.

The contrast control sets the difference between the darkest and lightest parts of the image. Again, you turn this down in a dark room so the bright areas are not uncomfortable to watch.

To your question, using both controls to reduce the beam energy of the brightest portions of the image will extend the life of both the electron gun and the phosphor. Enough to matter ... don't know.

ak
 

Nigel Goodwin

Super Moderator
Most Helpful Member
If I reduce the brightness of the CRT TV, will the tube have a very long life? some people say that this is a myth and the only solution is to decrease the voltage of the filament using a resistor but I have little experience to perform this procedure
It's mostly a myth - and I would suggest not worth doing.

There are essentially two 'wear out' mechanisms:

1) The cathode - this generates the electrons, and is directly dependent on the heater in order to work. Less heat means less electrons, so it's self defeating to reduce the heater voltage - and a common 'boost' technique was to add an extra transformer to boost the heater voltage, and extend the life of the tube.

2) The phosphors - the phosphors, just like in a fluorescent tube, age and wear, rapidly at first (which is what causes screen burn on CRT's and Plasma) and then gradually after that. This wear is rarely a problem, and regunned CRT's still used the original old phosphor.

Basically, to make it last as long as possible, use it as little as possible - we had an old-lady a very long time ago who bought a B&W TV from us - and she never turned it off. She simply turned the volume and brightness right down - and while this is good for reliability (it never once went wrong), the CRT wore out in about 5 years.
 

KeepItSimpleStupid

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Most Helpful Member
I worked on a CRT terminal and the brightness was uncontrollable. It was an internal tube short. CRT brightners were used on older sets,
Probably, the lower the filament voltage the better because the filament is more robust, but it costs more to make.

Then there is the object thrown at the CRT.

Color TV's had a set up switch where you would set the convergence of the beams because the Earth magnetic field changed the deflection.

On the other end of the spectrum, I've worked with 30 killowatt electron beams. they are nothing to sneeze at.

At the other end, the electron optics on a scanning electron microscope. The possibilty of shorts was a common occurance and the power supply had to handle that. The filament had to be aligned, both course and fine adjustments.

As Nigel just said, the phosphors can be damaged with what's called burn-in. it's really evident with CRT terminals/

The Trinitron is a really nice CRT. If you look really close there are a couple of wires down the face of the tube suspending the aperature. I have a home set with a trinitron tube and my first monitor for a macintosh computer had a trinitron. It suffered from burn-in.

I recently got a signed copy of The Cathode-ray Tube, and applications through a group buy indirect from the author. Peter A Keller, isbn 0-9631559-0-3. it's hardbound and 300+ pages. I haven;t read it yet, but I skimmed through it.

The section on reliability says they were ruggedized for the military and the Space Shuttle. primary improvements were high efficient phosphor, low deflection angle and the changing of the connector to wire leads.

At one point, The CRT and Yolk were pre-aligned at the factory.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Color TV's had a set up switch where you would set the convergence of the beams because the Earth magnetic field changed the deflection.
Not quite, there was no 'switch', on very old colour sets there was a huge variety of adjustments, both mechanical and electrical. The convergence wasn't affected by magnetic fields, that was the purity - completely different things. Basically you had static and dynamic adjustments for both, and you did the static first, followed by the dynamic - and purity before convergence.

At one point, The CRT and Yolk were pre-aligned at the factory.
They were called PIL tubes - and (as far as I know) the first set to use one was the Thorn 9000 series, a unique set in many ways.

It was a great relief once PIL tubes appeared, it made life MUCH easier :D - however, NOT for Trinitron tubes, presumably their limitations meant it wasn't possible to create PIL Trinitron tubes?. Their 'unusual' design also meant they had vastly more setting up required, including sticking little magnets all over the bowl of the CRT to try and correct the errors.
 
I have a CRT 29 "Toshiba curved screen and I use it constantly on the PS2 and I have another CRT 29" flat Philco stored in reserve which tips do you recommend?
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
Not quite, there was no 'switch', on very old colour sets there was a huge variety of adjustments, both mechanical and electrical. The convergence wasn't affected by magnetic fields, that was the purity - completely different things. Basically you had static and dynamic adjustments for both, and you did the static first, followed by the dynamic - and purity before convergence.
My point was to make the reference brief. Thanks for expanding.
 

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