Posted by panteltje on 11/07/07 13:15

On 7 nov, 01:36, "Bob Myers" <nospample...@address.invalid> wrote:
> "Jan Panteltje" <pNaonStpealm...@yahoo.com> wrote in message
>
> news:fgqhir$v9j$1@news.datemas.de...
>
> > On a sunny day (Tue, 6 Nov 2007 12:20:43 -0700) it happened "Bob Myers"
> > <nospample...@address.invalid> wrote in
> > <fgqeu2$5c...@usenet01.boi.hp.com>:
>
> >>The shortest-lived component in terms of useful service
> >>life is, of course, the tube itself.
>
> > I think not.
> > I have had a TV repair shop for many years.
> > CRT replacement is relatively rare compared to other problems,
> > like HV, bad joints (thermal), dried out electrolytics, etc.
>
> Read what I said again - the CRT is the shortest-lived
> single COMPONENT.

No, I doubt that, as I mentioned electrolytic capacitors, solder
joints
due to thermal stress, all have a shorter life.
It depends a bit on how you define 'life' in this case,
a bit less brightness from CRT phosphors is easily compensated by
a bit more drive (say contrast) and or brightness.


> > My Samsung Syncmaster CRT did 6 years at 12 hours a day (makes
> > 25632 hours) before I retired it (it is in the attic) this
> > summer, with NO noticeable decrease in anything (brightness,
> > white balance, contrast, convergence etc).
>
> You checked it by eyeball, or did you actually measure the
> brightness?

Well, If you were to do this right, then you would have:
For a new set, measure beam current, and luminance for
a red, green and blue screen.
Also measure EHT, and focus voltages, screen voltages on the tube.
Then after say 25000 hours measure it again.
And to see if it is phosphor you'd have to increase beam current
for the same brightness, if you need more beam current (with all
other parameters equal) for the same brightness, then it is likely
phosphors.
etc.
In this case I did not do that clearly, but I have fixed lighting and
what I normally did, is set white to the same brightness as the CRT
monitor frame.
That is a very precise point, (does not work with the LCD it has a
black case).
But you could use a piece of white paper.
Any loss of light output would have to be compensated for by a
different
knob position of contrast.
(Set black first with brightness, then white with contrast).
I also had a Philips monitor, that needed more and more brightness,
finally opened it up, adjusted the screen voltages and focus.
Samsung monitors are in a quality range that I am very happy with..


> Putting a brand-new monitor next to one that's
> been in service for a few years is very often a literally eye-
> opening experience.
>
> > That estimate could be right.
> > But I must point out that the life expectancy of a fluorescent
> > tube in a LCD is likely much lower then that of a CRT.
> > Maybe once LED backlights are more common, things will improve.
>
> MTBFs of CCFL tubes are currently in the neighborhood
> of about 20-30k hours, barring mechanical damage; longer-lived
> tubes are possible, but at the cost of efficiency/brightness. LEDs
> will certainly improve the situation, as long as the number of
> individual devices is held within reason.

I do notice, as some other poster also remarked, that I
need to run the the Samsung LCD at zero to 30 percent
brightness, as it is extremely bright (indoors, artificial light).
Maybe running the CFL tubes at <= 30% will extend their life, wait and
see.

> > A main issue in LCD monitors is, that you are faced with digital
> > re-size, and digital de-interlace.
> > This reduces resolution by say half.
>
> De-interlacing is hardly a concern for PC monitors, unless we're
> talking about the "multifunction" or "multimedia" sort of monitor that
> also can play TV set and accept standard video.

And that is exactly what I use it for.
Digital satellite TV card in the PC.
Interesting discussion.
Regards
Jan

> Interlacing all by
> itself decreases vertical resolution by a factor of at least 30%, that's
> just the nature of the beast.
>
> Bob M.

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