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'[EE]:Monitor Life'
2001\08\09@115342 by robertf

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Hello,

I have a pc that is always
running but not viewed all the
time except for about once to
several time a day depending
on the activity. Is it better
to turn it on/off or lower the
brightness and the contrast?
Other sugestions?
I use DMPS on one and because
the other two is older( not
dmps capable), I turn them
down.

Regards,

Robert Francisco

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2001\08\09@121814 by J.Feldhaar

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Hi Robert,

a good (but cumbersome) solution is to turn the filament off. Switching
is dangerous 'cos it might be at HV potential. Could be done with an
optocoupler...
This way the CRT screen won't age because is it not shelled with
electrons.

Greets
Jochen Feldhaar DH6FAZ

robertf schrieb:

{Quote hidden}

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2001\08\09@122631 by Douglas Butler

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I would turn down the brightness and adjust contrast as required.  My PC
at work I only turn off for weekends, unless there is stormy weather and
we might lose power in which case I turn it off overnight.

Sherpa Doug

> {Original Message removed}

2001\08\09@124156 by . Gianna, MS, CCSE, ACE/ADM

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It really depends on HOW that PC is used -- if it is all interactive, you can
turn it on when needed, off when not needed.
(makes the room a little cooler, saves a bit of energy). If the PC gives you a
visula ALERT -- then you should leave it on, but turn it down.

It reminds me of a server room at IBM where I used to work years ago -- I would
have the system architect come in the room and turn off monitors for servers
that "didn't do anything" since there was no point in wasting the monitors on
machines that never showed anything anyway.

This was soon followed a few weeks later by an engineer who walked into the
room, said "maybe it's just me ...", turned on one of the monitors, "but I would
want to leave the monitor ON for my domain controller so I would know when it
crashed", and sure enough as the screen came on, there was the error message
that no one saw ... had the monitor been on, we would have known sooner to
reboot the server . . . "for the pennies in electricity it saves, it's not worth
it to bring down a line that loses $50,000 an hour..."

you could always tell which one visited the room by whether the monitors were on
or off ... :)


So the point is, if you would miss something IMPORTANT, then don't turn it off.
Otherwise, turn it off . . .


Dave Gianna, MS, CCSE, CCSI, NSA, ACE/ADM
Technical Sales Engineer
Security Technologies Group
(914) 829-7351
Westcon, Inc. <http://www.westcon.com>
520 White Plains Road
Tarrytown, NY 10591

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I would turn down the brightness and adjust contrast as required.  My PC
at work I only turn off for weekends, unless there is stormy weather and
we might lose power in which case I turn it off overnight.

Sherpa Doug

> {Original Message removed}

2001\08\09@221314 by robertf

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The pc is doing something. I
just occasionally check up on
it's progress, make an
adjustment on the process and
continues...
Is turning off the filament
the same as turning down the
brightness?
I realise there are HV
potential inside, not being
equipped with the right
trainning and with HV tools,
I'd rather do things on the
outside.

Thanks for the replies so far.

Robert F

{Original Message removed}

2001\08\10@044942 by J.Feldhaar

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Hi Robert,

I was thinking too much of an oscilloscope CRT, sorry.
Most monitors are at "normal" voltage level with the cathode, so
switching is possible. We used it in a Commodore 2001 (known as the
"PET"), which was running a HAM RTTY repeater application, and there the
supply of the monitor couldn't be switched separately from the computer.

Now for the difference between turning down the brightness, and
switching the filament ("the heater"): Turning down the brightness, the
cathode is still heated, but due to the altered voltage levels around
the cathode, the electron beam does not go towards the screen. Switching
off the filament does not generate this electron cloud around the
cathode, with the same result. Not heating the cathode may (I'm not
sure, perhaps Roman can give a tip here) extend life.

Greets
Jochen Feldhaar DH6FAZ

robertf schrieb:

{Quote hidden}

> {Original Message removed}

2001\08\10@054718 by Vasile Surducan

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On Fri, 10 Aug 2001, J.Feldhaar wrote:

> the cathode, the electron beam does not go towards the screen. Switching
> off the filament does not generate this electron cloud around the
> cathode, with the same result. Not heating the cathode may (I'm not
> sure, perhaps Roman can give a tip here) extend life.
>
 In any case shuting off the filament will not extend the tube life.
[ all modern TV's have keeped on the filament at 1/2 nominal voltage or
less, all the time when are plugged in ]
I'm involved (more or less) in repairing garbages ( various tipes of
monitors caming here from all the world including US, Taiwan, Europe,
China, Japan as defective and not reparable )
The smartest types have a feature which shut at 1/2 the nominal
filament voltage when monitor is in stand-by and start with a
progressive HV value . The real problem comes when
the tube is supplied with HV ( 27 to 35 KV ). An important quantity of
emisive material which is deposed on the cathodes is trough away in the
switching moment ( and not the same quantity from all RGB catodes). If
there is no filament is worse on this moment. Ideally the order
in which the tube electrodes must be polarised are:
the filament, a sufficient delay to ensure heating, acceleratig and post
accelerating grilles, then HV and only then RGB cathodes ( contrast ), and
luminosity signals.
In reality all are suplied from the same HV transformer or from two
different transformers connected in cascade ( japanese models ).
Also, in time the filament become oxidable, and must be purged with a
simple HV discharging device.
The best way is to drop the old tube to the garbage. However a good
tube may work at least 15 years.( see Toshiba, Sony or Philips tubes )
Never with Zenith ( americans ) or Chung Wha ( chinese ) tubes.
Vasile

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2001\08\12@055626 by Roman Black

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J.Feldhaar wrote:
>
> Hi Robert,
>
> I was thinking too much of an oscilloscope CRT, sorry.
> Most monitors are at "normal" voltage level with the cathode, so
> switching is possible. We used it in a Commodore 2001 (known as the
> "PET"), which was running a HAM RTTY repeater application, and there the
> supply of the monitor couldn't be switched separately from the computer.
>
> Now for the difference between turning down the brightness, and
> switching the filament ("the heater"): Turning down the brightness, the
> cathode is still heated, but due to the altered voltage levels around
> the cathode, the electron beam does not go towards the screen. Switching
> off the filament does not generate this electron cloud around the
> cathode, with the same result. Not heating the cathode may (I'm not
> sure, perhaps Roman can give a tip here) extend life.


The tube ageing we see the most is usually
the green gun, as it is driven harder, I think
a pure white screen on your TV tube is about
55% green, 35% red, 10% blue guns driven,
but it's been many years since I had to write
those figures on a test paper!

The brighter the screen is, the worse it
ages, and yes overheating of the cathodes
causes faster ageing. Dad's TV is 24 yrs old
now, I replace some caps every few years
and he always likes it a bit dark. Still a
decent picture and probably added ten years to
it's life running it a bit dark.

New picture tubes just are not the same
quality, I see 4yr old portables with worn out
tubes.

Re the question above when the picture is darker
there is less beam current, so cathode life
is increased. Maybe electron emission depends
greatly on cathode current, not just heating.

One point, many modern sets fail if often left
on black screen, like AV channel, the PSU is
still generating full HT volts but there is
no beam current, and this can strain parts
that are already skimpy.

So my answer is turning down the brighness
WILL give a lot longer tube life, less wear
on the cathodes and the phosphor dots.
Ummm, screensaver software anyone?? :o)
-Roman

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2001\08\12@114646 by robertf

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Thanks Roman, it makes sense.
I think I will just turn the
bright/contrast down instead
of fully turning them off.
This also brings up the screen
a little sooner when I do need
to look at my data.  One
observation - When I was
shopping for my monitor I
noticed that every monitor
with the exception of a
trinitron tube has their
bright/contrast controls set
to (near) max to get decent
picture.

Thanks for the responses from
the list

regards    - robertf

{Original Message removed}

2001\08\12@120643 by Jeff DeMaagd

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----- Original Message -----
From: robertf <EraseMErobertfspam_OUTspamTakeThisOuTMICROBALANCE.COM>

> observation - When I was shopping for my monitor I
> noticed that every monitor with the exception of a
> trinitron tube has their bright/contrast controls set
> to (near) max to get decent picture.

Maybe Roman can explain this better than I can or contradict me with better
info, but Trinitron displays often seem ore efficient.  Other manufacturers
seem to put up products with intentionally screwed up picture settings just
to make them look good on the retail floor under bright lighting.

It is often a good idea to turn the brightness down to just above a minimum
manageable level.  I have no clue what to do for computer monitors but what
some people do for home theater and TVs is buy a calibration disc to "tune
up" the display for the environment.

Jeff

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2001\08\12@120650 by Roman Black

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robertf wrote:
>
> Thanks Roman, it makes sense.

Anytime! :o)

> One
> observation - When I was
> shopping for my monitor I
> noticed that every monitor
> with the exception of a
> trinitron tube has their
> bright/contrast controls set
> to (near) max to get decent
> picture.

Maybe you're in a BRIGHT room??
You should have screen, keyboard, desk etc
all about the same light intensity, so that
your pupil doesn't have to re-size every
time you look up or down. :o)
-Roman

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2001\08\13@162719 by Peter L. Peres

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I think that most people forget that TVs for home consumption are not
meant to be viewed when bright lights are on. Typical illumination in a
home while watching TV is expected to be between 50 and 200 lux afair.

This is not the case for projection units designed to work in daylight.
The difference is from ~80W input to a 21" TV set to >400W input to a
projection unit with 2.2 meter screen. The screen projection should lose
(power should be ~16x for same brightness) but it does not because the
viewing angle is narrower and other efficiency factors. It can appear
twiec as bright as a TV alongside it. (the TV only puts about 20W of power
into the screen luminance proper out of the 80 input). Did anyone notice
how displays at exhibits carefully place TVs, plasma screens and
projection screens so they can't be watched and compared at the same time
by the same person ? ;-). (I know there are exceptions, and I know who
they are).

The lifetime of four years of a new low cost picture tube is not very low,
assuming that the unit was operated all the time. Do the hours count and
you will see that the hours count will approximately match or exceed the
expected hour count for these devices.

Older tubes had much thicker cathode coating than now and it was of
different formulation (pretty hot afaik ;-). Nowadays the coatings are
thinner and more 'optimized'.

The Trinitron has slightly higher efficiency because it uses a vertical
wire mesh instead of a slotted mask afair. This has higher transparency to
electrons. I am using a trinitron screen both here and at work so I
know ;-).

Peter

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