Notes on the Troubleshooting and Repair of Computer and Video Monitors


  13.8) Digital versus analog controls on monitors and picture quality

"Could someone tell me if there's a noticeable difference in picture quality
 between analog and digital monitors?  Is digital worth the extra money?"

There is no inherent reason for a digital monitor to have a better picture but
as a practical matter, I would expect this to be the case in the vast majority
of monitors - especially models from the same manufacturer.  The digital
monitors will be the ones that the designers concentrate on.  Digital controls
(both those you can access and those used only during setup at the time of
manufacturing or servicing) permit more flexibility in setting parameters and
automated more consistent adjustments on the assembly line (at least this is
possible in principle).

For the average not terribly fussy PC user, the major difference is in the
convenience of not having to adjust size and position whenever the scan
rate changes.  In my opinion, while the price difference between monitors
having analog or digital controls but with the same screen size, resolution,
and scan range specifications may seem excessive, the added convenience of
digital controls and scan rate parameter memory makes the added cost well

  13.9) Should I be concerned about very frequent scan rate switching

This question arises in a PC software development environment where the
programmer needs to go back and forth between a Windows display and
a DOS debugger, for example.

Obviously, without knowing the precise design of your monitor, there can
be no definitive answer.  It is true that some older monitors blew up
if you looked at them the wrong way.  Newer monitors from well known
manufacturers like Nokia, NEC, and many others are designed with a moderate
amount of scan switching in mind.  However this is stressful for the monitor's
power supply and deflection circuitry.  I would suggest that you use a
dedicated mono monitor for debugging if you really are switching multiple times
per minute.  If you cannot afford the space, you can probably assume that
if the first few days of this kind of treatment have not induced a failure,
the monitor is robust enough to withstand it indefinitely.  If you really
are switching many times per minute 8 hours or more a day, then what may
wear out are the internal relays (the clicks you hear are from these).
You are still talking about years, however.  They are rated in 100s of 
thousands or millions of operations when used within their ratings.

Or, just go for the peace of mind of an extended warranty or service contract.

  13.10) What is monitor video bandwidth and why is it important?

(From: Bob Myers (myers@fc.hp.com)).

Video bandwidth is an indication of the frequency range over which the
monitor's video amplifiers are capable of doing their job, which is to
translate the video signal at the monitor inputs (about 0.7 volt, peak-to-
peak) to something like 35-40V peak-to-peak at the CRT cathodes.  Higher
bandwidths ARE better, UP TO A POINT.

The bandwidth required is NOT given by multiplying the numbers in the
format (what most call the "resolution") by the refresh rate; even allowing
for the required blanking time, what THAT gives you is the pixel rate or
"pixel clock".  As the fastest thing that happens in a video signal is
one dot on followed by one dot off, the fastest FUNDAMENTAL frequency in 
the video signal is half the pixel clock.  Normally, you might think you'd
want to cover some of the harmonis to "sharpen up" the pixel edge, but
that's actually less important than you might think (in part due to the
fact that the CRT screen itself, being made up of discrete dots of color,
already has the effect of "sharpening up" the image AND limiting how
sharp it's going to get, anyway).

There's also the problem of "bandwidth" not being measured or speced
consistently by all manufacturers, making it difficult to compare one
product to another.  Some simply give a "max. video rate supported" number,
which is about as useless a spec as one can imagine.  (It's just telling
you the pixel rate of the fastest timing supported - but says nothing about
the image quality at that timing!)  Still, a claimed bandwidth of about
2/3 to 3/4 of the fastest pixel rate to be used should indicate adequate
performance - beyond that, you need to compare products with the good
ol' Mark I eyeball.  Using this rule of thumb, a monitor intended for use
at 1280 x 1024, 75 Hz (a 135 MHz pixel rate) needs a speced amp bandwidth
of around 100 MHz.  (But just to show how far you can trust this particular
number, I know of a product which does a very nice job of displaying
1600 x 1200 at 75 Hz - slightly more than a 200 MHz pixel rate - but which
has a video amp bandwidth of only about 100 MHz, if measured per certain

I find the rise and fall time of a full-scale (white to black or black to
white) video signal, as measured at the cathode, to be a much better spec,
and here would look for something not slower than 2/3 of the pixel period
for the timing of interest.  But these numbers are rarely quoted in 
consumer-oriented spec sheets, and even these take some care in applying.

  13.11) Why a good monitor may produce a fuzzy picture

The ultimate sharpness of the picture on your monitor depends on many factors
including but not limited to:

1. Focus of the electron beam spot(s) at the face of the CRT.

   Affected by: quality of the CRT and its supporting circuitry and adjustment
   of focus control(s).

2. Convergence of the RGB electron beams at each point on the face of the CRT.
   Affected by: quality of the CRT, deflection components, and how carefully
   the convergence adjustments were done during manufacture (or repair).  In
   many cases, it is this last item that is most critical.  Bad quality control
   during final setup can ruin a monitor manufacturer's reputation - and has.

3. Moire reduction (if any or if enabled) reduces the effective sharpness of
   the electron beam either through actual defocusing or a high frequency
   dither.  IMO, the net effect is almost always bad.

   Affected by: enabling and magnitude of moire reduction.

Items (1) through (3) are somewhat independent (though not entirely) of scan
rate.  The newest high-end monitors have a fairly comprehensive set of digital
(on-screen) adjustments for these but may still not produce acceptable results
for every monitor.

4. Bandwidth of the video amplifiers in the monitor - essentially how quickly
   the intensity can be altered by the video signal.

   Affected by: design of video amplifier circuitry and circuit board layout.
   This used to be much more of an art than it is today.  Integrated circuits
   have replaced many of the discrete components used in the past resulting
   in simple designs with clean circuit board layouts.

5. Bandwidth of the digital to analog converter (D/A, DAC, or RAMDAC) of the
   video card.

   Affected by: DAC or RAMDAC chip used, supporting circuitry, and video card
   board layout.  As with (3), these are largely cookbook designs these days.

6. Dispersion in the video cable - how smeared out the video signal becomes
   traveling through the cable.

   Affected by: quality and length of video cable.  Since cables often come
   attached to the monitor nowadays, you don't have much control of this.
   Just don't add problems such as switchboxes.

7. Reflections from any impedance discontinuities in the cable - video card
   DAC, video  card connector, monitor connector, monitor video amplifier
   input, monitor termination.  All of these will introduce just a bit of
   mismatch - or perhaps much more - which will add up to either barely
   detectable fuzziness or totally unacceptable ghosting or ringing at
   vertical edges.

   Affected by: connectors and circuit board layouts of both video card and
   monitor input as well as any additional connectors or a switchbox.

Items (4) through (7) are heavily dependent on scan rate since higher scan
rates translate into higher video bandwidth.  Any degradation of the edges
of the video signal - transitions from black to white, for example - will
be much more visible at the higher scan rates - they will be spread out
resulting in pronounced blurring, ghosting, or ringing.

Thus, it is critical to use the highest quality components wherever possible.
While you don't have control over what is on your video card and inside your
monitor, selecting a high quality video card and monitor should help.  If you
have the option to use a BNC cable (at least your monitor has BNC jacks on
the back), try out a high quality BNC cable - you may be pleasantly surprised
at the improvement in edge definition and overall sharpness.

  13.12) Ghosts - card or monitor?

(From: Bob Myers (myers@fc.hp.com)).

This isn't as simple as it may appear.  'Ghosts' are caused by reflections
of the video signal edges, caused by impedance mismatches between the driver
(graphics card), the video cable, and the monitor video inputs.  Add in the
problems caused by the video connectors, and you wind up having to say that
this is really (most often) a system problem, and all the parts get some of
the blame.

With that said, the practical answer is that you should avoid using anything
other than a single, reasonably-good-quality video cable, with decent 
connectors, between your PC and monitor, this being the part that you have
the most control over.  The more breaks in the cable  - adding extension
cables, switchboxes, etc. - the more chances you have for a mismatch in the
line.  BNC connectors (or the new VESA EVC connector) are MUCH better in this
regard than the 15-pin D "VGA" connector (although if you're getting good
results with the D connector, don't worry about it).  Also, do NOT make the
mistake of using anything other than 75 ohm coax for your video cables.  
Just to mention one common mistake, LAN cable is *50* ohms, so it's NOT
going to work here!

If you've done all you can with the cable, the next place to go is the monitor
itself; there's probably something wrong with the video input termination.
By the way, a simple way to confirm that what you're seeing IS a ghosting
(reflections) sort of problem is to use a DIFFERENT LENGTH of the video cable.
Since the ghost is the result of a reflection going from the monitor back 
to the PC and then back up the line, the length of the cable affects where
the ghost appears relative the edge which caused it.  Inserting a
longer cable moves the ghost out (to the right), while a shorter one will
move it closer in (to the left).  If you change cable lengths and the ghost
doesn't move, you most likely have a problem within the monitor itself, past
the video inputs.

BTW, longer cables may also make the ghost less distinct, due to the increased
attenuation of the signal by the cable.  Unfortunately, the longer cable
also means more attenuation of the video signals that you WANT, in addition

  13.13) Extension cables and monitor ghosting

(From: Bob Myers (myers@fc.hp.com)).

With an extension cable, there is the chance that this ghost is being caused
by an impedance mismatch AT THE CONNECTOR OF THE EXTENSION; unless the
cable is completely the wrong impedance, it is unlikely that the cable
itself (meaning the actual "wire") is the culprit.  But any break in the
cable (connectors, switchboxes, etc.) is a chance for a mismatch.

But before blaming the cable, there's another possibility to check out.
One commone source of ghosting is a poor termination of the line at the
monitor itself and at the graphics card driving it.  It can look worse with
an extension simply due to the extra cable length moving the "ghost" farther
away from the image causing it.  (The ghost is, after all, just a reflected
signal that went back DOWN the cable, got reflected again at the controller,
and sent back up to the monitor.  Added cable length makes this round trip
longer, and moves the ghost farther to the right of the original edge in the
displayed image.)  If this is the case, the you will also see the ghost
without the extension - it'll simply be much closer to the original edge
that it's "ghosting".  In that case, a better extension cable can actually
make the appearance of the ghost worse - a lower-loss cable means that more
of the reflection will get through back to the monitor!

If it is being caused by the extension cable, you may get better results
by using BNC connections instead of the D-sub at the point where the cables
mate.  The D-sub is a pretty poor connector in terms of providing the proper
impedance.  Using a pair of 15D-to-5-BNCs back to back may give better

  13.14) Driving multiple monitors from a single PC

Where BNC monitors are involved and daisychaining is acceptable, additional
circuitry is generally not required for reasonable distances.  BNC cables
for R, G, B, and possibly H and V sync, are run from the source to each monitor
in turn with only the last one being terminated in 75 ohms (the others MUST
be Hi-Z).

However, it is not possible to drive multiple monitors in a star configuration
without buffering the signals.  In addition, some newer BNC monitors do not
have a Hi-Z option for termination so daisychaining is not even an option with
these.  In either of these cases, what is needed is a distribution buffer
amplifier.  One such circuit is shown at:

* http://www.anatekcorp.com/driving.htm

This includes simple emitter follower circuits for each high speed signal.

  13.15) Using a PC as a monitor test pattern generator

Almost any PC with at least a medium performance SVGA video card can
be programmed for a wide range of resolution options, dot clocks,
horizontal and vertical sync timing, and sync polarity.  Some can
be programmed to generate composite sync and sync-on-green as well.

DOS/Windows/Win95 will suffice for most PC applications using drivers
supplied by the video card manufacturer but for complete flexibility,
run under Linux - take a look at the Xfree86 documentation for more

Test patterns can be created with any graphics applications and then
saved for rapid recall.

The following web sites also have some test pattern programs available for

(Comments from: Byron Miller (byron13@pacwest.net)).

* http://www.nokia.com/products/monitor_test.html

  Very good, color, thorough, professional.

* http://www.zdnet.com/cshopper/shopguid/0695/subt.html#download

  Small and very basic program in B/W.

Of course, for different output levels and impedances you will need some
extra electronics. A normal SVGA card only produces R,G,B video and H and
V sync signals compatible with doubly terminated 75 ohm cables.  As noted,
some will generate composite sync and/or sync-on-green.  See the
"Sync-on-Green FAQ" for more information on how to do this if your card
is not capable of it.  For NTSC/PAL video generation, additional hardware
will be needed.  See the section: "Displaying computer video on a TV".

  13.16) Using a TV tuner card in a PC

These ISA, EISA, or PCI cards put TV programs or other NTSC/PAL source
material into a window on your PC's monitor screen.  The question has come
up as to whether this will damage the monitor in the long term.

I would not think that there should be any problems unless you tend to turn
the brightness up much higher than normally used for computer activities.
If anything, the constantly changing picture will be better than a stationary
window.   However, moving it to different locations every so often will not

Similar comments apply to other types of image and video captures as well.

IMHO, I still think it is silly to use an expensive PC and monitor to watch TV.

  13.17) What is color temperature and what does it affect?

Some monitors have the capability of selecting or adjusting for the 'color
temperature' of the display.  NEC AcuColor on the 4/5/6FG series of monitors
is one example.

The terminology refers to the spectral output of an ideal black body source
at that actual physical temperature.  It essentially sets the appearance
of a white screen.  For example, a color temperature of 9300K will appear
blue-white while 6300K will appear yellow-white.

It only affects the relative balance of R,G,B and has nothing to do with
refresh rates or anything performance related.  Unless you are doing work
where the exact colors matter or are using multiple monitors where the
colors need to match, use whichever setting ismore pleasing

  13.18) What is this goop around some electrolytic capacitors and other components?

That goop is probably glue and generally harmless - it is there to hold
down the components aganst vibration.  I have heard of it sometimes
decomposing and shorting stuff out but I doubt you have that problem.

Therefore, unless you find a bad cap in the focus or related circuit, we
are still looking at a flyback problem.

  13.19) What does the flyback (LOPT) transformer do?

The typical flyback or Line OutPut Transformer (LOPT) consists of two parts:

1. A special transformer which in conjunction with the horizontal output
   transistor/deflection circuits boosts the B+ (120 V typical for a TV) of the
   low voltage power supply to the 20 to 30 KV for the CRT as well as provide
   various secondary lower voltages for other circuits.

   A HV rectifier turns the high voltage pulses into DC and the CRT capacitance
   smooths it.  The HV may be developed from a single winding with many many
   turns of wire or a lower voltage winding and a diode-capacitor voltage

   The various secondary voltages power the logic, tuner, video signal,
   vertical deflection circuits, and CRT filaments.  In fact, with many TV
   designs, the only power not derived from the flyback is for the keep-alive
   circuitry needed to maintain channel memory and provide startup drive to
   the horizontal deflection/high voltage system.

2. A voltage divider that provides the focus and screen supplies.  The pots
   are in this divider network - and these things fail resulting poor focus,
   uncontrolled brightness, or fluctuating focus and/or brightness.  A
   total short could also result in failure of other components like
   the horizontal output transistor.  In some monitors, the focus and screen
   divider and/or controls are external to the flyback and susceptible
   to dust and problems particularly on humid days.  The resistance of these
   circuits is so high that dirt or other contamination can easily provide
   a bypass path to ground especially when slightly damp.

  13.20) Tony's notes on setting convergence on older delta gun CRTs

(From: ard12@eng.cam.ac.uk (A.R. Duell))

The older delta-gun tubes (3 guns in a triangle, not in a line) can give 
**excellent** pictures, with very good convergence, provided:

1. You've set those 20-or-so presets correctly - a right pain as they 
   interact to some extent.

2. The CRT is set up in the final position - this type of tube is more 
   sensitive to external fields than the PIL type.

Both my delta-gun sets (a B&O 3200 chassis and a Barco CDCT2/51) have 
very clearly set out and labeled convergence panels, and you don't need a 
service manual to do them. The instructions in the Barco manual are 
something like:

"Apply crosshatch, and adjust the controls on the convergence board in 
the numbered order to converge the picture. The diagrams by each control 
show the effect".

Here's a very quick guide to delta gun convergence where the settings are
done using various adjustments on the neck of the CRT (if you don't have a 
service manual but do know what each control does, and where they all are -
otherwise, follow the instructions in the service manual --- sam): 

1. Apply a white crosshatch or dot pattern to the set. Don't try and 
   converge on anything else - you'll go insane. It's useful to be able to 
   switch between those 2 patterns.

2. Before you start, set the height, width, linearity, pincushion, etc. They
   will interact with the convergence. Also check PSU voltages, and the EHT
   voltage if it's adjustable. That's where you do need a service manual, I 

3. Turn off the blue gun using the A1 switch, and use the red and green 
   static radial controls to get a yellow croshatch in the middle of the 
   screen. These controls may be electrical presets, or may be movable 
   magnets on the radial convergence yoke (the Y-shaped think behind the 
   deflection yoke).

4. Turn on the blue gun and use the 2 blue static controls (radial and 
   lateral) to align the blue and yellow crosshatches at the center of the 
   screen. Some manufacturers recommend turning off the green gun when doing 
   this, and aligning red with blue (using *only* the blue controls, of 
   course), but I prefer to align blue with yellow, as it gives a check on 
   the overall convergence of the tube.

5. Turn off the blue gun again. Now the fun starts - dynamic convergence. 
   The first adjustments align the red and green crosshatches near the edges - 
   I normally do the top and bottom first. There will be 2 controls for 
   this, either a top and a bottom, or a shift and a linearity. The second 
   type is a *pain* to do, as it's not uncommon for it to affect the static 

6. Getting the red and green verticals aligned near the edges is a 
   similar process. 

7. You now have (hopefully) a yellow crosshatch over the entire screen. 

8. Now to align the blue. This is a lot worse, although the principle is 
   the same. Turn on the blue gun again, and check the static (center) 

9. To align the blue lines with the yellow ones, you'll find not only 
   shift controls, but also slope controls. Use the shift controls to align 
   the centers of the lines and the slope controls to get the endpoints 
   right. These interact to some extent. You'll need to fiddle with the 
   controls for a bit to work out what they do, even if you have the manual.

The convergence over the entire screen should now be good....

A word of warning here... The purity is set by ring magnets on almost all 
colour CRTs, but on PIL tubes, there are other ring magnets as well - 
like static convergence. Make sure you know what you are adjusting.

  13.21) Jerry's comments on convergence and other advanced CRT adjustments

(From: Jerry G. (jerryg@total.net)).

Convergence alignment is not something you can do yourself unless you have the
proper calibration instruments and skills.  It takes lots of experience and
time.  There are published specs for most of the good monitors.  Most of the
time they are as follows:

There is the 'A area', 'B area', and 'C area'.  On a 15 inch monitor the A
area would be a diameter of about 4 inches.  The B area would be about 7.5
inches.  The C area would be the outside areas including the corners.  These
numbers are approximate.  There are actually standard specs for these areas.
They are expressed in percentage of screen viewing area.  Therefore the inches
would vary with the CRT size.

The higher the price (quality) of the monitor CRT, yoke, and scanning control
circuits, the tighter the convergence can be aligned by the technician.  For
the A area on a good monitor, the maximum error should not exceed 0.1 mm.  For
the B area it should not exceed more than about 0.25 mm.  And for the C area,
it can be allowed up to about 0.3 mm.  Most of the monitors that I have
repaired, seen, and used did not meet these specs unless they were rather
expensive.  With these specs there would not be any real visible
misconvergence unless you put your nose very close to the screen...  A lot of
the ones in the medium price range they were about 0.15 mm error in the A
area, about 0.4 in the B and greater than in the C area.  This also annoys me
because I am very critical.

If one has the skills and test gear he or she can do a better job on most
monitors.  It is a question of the time involved.  To see the convergence
errors a grating or crosshatch pattern is used.  A full raster color generator
is required for the purity adjustments as well.  This is necessary to align
the landing points of the CRT guns.  The exact center reference and purity
adjustments are done with the ring magnets on the CRT neck.  The yoke position
angle adjustments are also done for the side and top-bottom skewing as well.
Everything interacts!

The corners are done with various sorts of slip or edge magnets.  As for
corner convergence skewing, button magnets are used.  The color purity will
be effected as you go, and must be also corrected.  These adjustments interact
on one another, and the processes continues until the convergence and purity
are good at the same time...!

I don't recommend the amateur or hobbiest, or even the do-it-yourselfer to
attempt this alignment procedure.  The test gear would exceed the cost of a
really good monitor anyways...!!! And without the proper skills required, he or
she would only make it worse anyways...

As for purity specs, the color change from any corner to any corner must not
exceed an error of more than 200 degrees Kelvin.  The error in the B area
should not exceed 300 degrees kelvin.  This applies to a white raster.  Most
of the monitors I see don't get better than about 300 degrees Kelvin.  And
some are even 1000 out! The purity errors are best checked with a full Red
raster using 100 % saturation.  Then the other color vector angles are checked
with cyan, and then magenta.  The color temperature stability should be the
same in all aspects.

A color spectrometer should be used to judge this error factor.  As far as the
eye is concerned, it will see a purity error of more than about 500 degrees
Kelvin if the person knows what to look for...

When changing the CRT, this alignment must be done completely.  Most shops do
not even employ people who are skilled to a proper alignment, or don't even
own the instruments to do it right, and the poor customer get back a monitor
that is not in specs...!

  13.22) Use of surge suppressors and line filters

Should you always use a surge suppressor outlet strip or line circuit?
Sure, it shouldn't hurt.  Just don't depend on these to provide protection
under all circumstances.  Some are better than others and the marketing
blurb is at best of little help in making an informed selection.  Product
literature - unless it is backed up by testing from a reputable lab - is
usually pretty useless and often confusing.

Line filters can also be useful if power in you area is noisy or prone
to spikes or dips.

However, keep in mind that most well designed electronic equipment
already includes both surge suppressors like MOVs as well as L-C
line filters.  More is not necessarily better but may move the point
of failure to a readily accessible outlet strip rather than the innards
of your equipment if damage occurs.

Very effective protection is possible through the use of a UPS (Uninterruptible
Power Supply) which always runs the equipment off its battery from the internal
inverter (not all do).  This provides very effective isolation power line
problems as the battery acts as a huge capacitor.  If something is damaged,
it will likely be the UPS and not your expensive equipment.  Another option
is to use a constant voltage transformer (SOLA) which provides voltage
regulation, line conditioning, and isolation from power spikes and surges.

It is still best to unplug everything if the air raid sirens go off or
you see an elephant wearing thick glasses running through the neighborhood
(or an impending lightning storm).

  13.23) GFCI tripping with monitor (or other high tech equipment)

Ground Fault Circuit Interrupters (GFCIs) are very important for
minimizing shock hazards in kitchens, bathrooms, outdoors and other
potentially wet areas.  They are now generally required by the NEC Code
in these locations.  However, what the GFCI detects to protect people - an
imbalance in the currents in the Hot and Neutral wires caused possibly
by someone touching a live conductor - may exist safely by design in 3
wire grounded electronic equipment and result in false tripping of the
GFCI.  The reason is that there are usually small capacitors between
all three wire - Hot, Neutral, and Ground in the RFI line filters of
computer monitors, PCs, and printers.  At power-on and even while operating,
there may be enough leakage current through the capacitors between Hot
and Ground in particular to trip the GFCI.  Even for ungrounded 2 wire
devices, the power-on surge into inductive or capacitive loads like switching
power supplies may falsely trip the GFCI.  This is more likely to happen
with multiple devices plugged into the same GFCI protected outlet especially
if they are controlled by a common power switch.

Therefore, I do not recommend the use of a GFCI for computer equipment as
long as all 3 wire devices are connected to properly grounded circuits.
The safety ground provides all the protection that is needed.

  13.24) Monitors on foreign power

Using a monitor on a different voltage or frequency is usually not a
serious problem.

Your PC and monitor should be fine requiring at most a transformer (not
just an adapter for heating appliances, however) to convert the voltage.
They both use witching power supplies which don't care about the line

Some power supplies are universal - they automatically adapt to the
voltage they are fed without requiring even a transformer but don't
assume this - check you user manual or contact the manufacturer(s) to
determine if jumpers or switches need to be changed.  You could blow
up the PC or monitor by attempting to run it on 220 VAC when set of
115 VAC.  If you are lucky, only a fuse will blow but don't count on it.

For non-switching power supply devices like printers and wall adapters
that use line power transformers, in addition to matching the voltage
(or setting jumpers or switches), running on a lower line frequency
may be a problem.  There is a slight chance that the power transformer
will overheat on 50 Hz if designed for 60 Hz.  (The other way around should
be fine.)  It is best to check the nameplate - it should tell you.  If it
does not, then best to contact the manufacturer.

  13.25) Lifespans of Monitors

(From: Bob Myers (myers@fc.hp.com)).

Most manufacturers will quote an MTBF (Mean Time Before Failure) of
somewhere in the 30,000 to 60,000 hour range, EXCLUSIVE OF the CRT.  The
typical CRT, without an extended-life cathode, is usually good for
10,000 to 15,000 hours before it reaches half of its initial brightness.
Note that, if you leave your monitor on all the time, a year is just about
8,000 hours.

The only "tuneup" that a monitor should need, exclusive of adjustments
needed following replacement of a failed component, would be video amplifier
and/or CRT biasing adjustments to compensate for the aging of the tube.
These are usually done only if you're using the thing in an application where
exact color/brightness matching is important.  Regular degaussing of the
unit may be needed, of course, but I'm not considering that a "tuneup" or

  13.26) How do monitors know when to enter power saving modes?

(Portions from Bob Myers (myers@fc.hp.com)).

If the monitor complies with the VESA DPMS (Display Power Management
Signalling) standard, it will go into power saving modes when either
horizontal or vertical sync is disabled. Different combinations of the
sync signals indicate different levels of power management, distinguished
by how much the power is reduced and the expected recovery time.  The
greater the power savings, the greater the recovery time is expected
to be.  For instance, one thing that may distinguish the greater power
savings states is turning off the CRT filament, something that you don't
recover from in just a second or two.

You can tell which power saving mode is active by how long the monitor
takes to come back to life:

1. Video blanking - image will appear instantly when any key is pressed
   since this is just a logic level inhibiting the video drivers.

2. Full shutdown - a warmup period of around 15 seconds will be needed
   for the image to reappear since the filaments of the CRT need to warmup.

  13.27) Monitor life, energy conservation, and laziness

A common misconception about the care and feeding of computer monitors is that
they should be left on all the time.  While there are some advantages to this,
there are many more disadvantages:

1. CRT Life: The life of a monitor is determined by the life of the CRT.
   The CRT is by far the most expensive single part and it is usually not
   worth repairing a monitor in which the CRT requires replacement.
   The brightness half-life of a CRT is usually about 10-15 K hours of on time
   independent of what is being displayed on the screen.  10 K hours
   is only a little more than a year.  By not turning the monitor off at
   night, you are reducing the life of the monitor by a factor of 2-3.
   Screen savers do not make any substantial difference especially with
   modern displays using X-Windows or MS Windows where the screen layout is
   not fixed.  With video display terminals, the text always came up in the
   same position and eventually burned impressions into the screen phosphor.

2. Component life: The heat generated inside a monitor tends to dry out parts
   like electrolytic capacitors thus shortening their life.  These effects are
   particularly severe at night during the summer when the air conditioning
   may be off but it is still a consideration year around.

3. Safety:  While electronic equipment designed and manufactured in accordance
   with the National Electrical Codes is very safe, there is always a small
   risk of catastrophic failure resulting in a fire.  With no one around,
   even with sprinklers and smoke alarms, such an failure could be much
   more disasterous.

4. Energy use:  While modern monitors use a lot less energy than their
   older cousins, the aggregate energy usage is not something to be ignored.
   A typical monitor uses between 60 and 200 Watts.  Thus at a $.10 per KWH
   electric rate such a monitor will cost between $48 and $160 a year
   for electricity.  During the night, 1/2 to 2/3 of this is wasted for
   every monitor that is left on.  If air conditioning is on during the
   night, then there is the additional energy usage needed to remove this
   heat as well - probably about half the cost of the electricity to run
   the monitor.

The popular rationalization for what is most often just laziness is that
power-on is a stressful time for any electronic device and reducing the
number of power cycles will prolong the life of the monitor.  With a properly
designed monitor, this is rarely an issue.  Can you recall the last time
a monitor blew up when it was turned on?  The other argument, which has more
basis in reality is that the thermal cycling resulting from turning a monitor
on and off will shorten its life.  It is true that such thermal stress can
contribute to various kinds of failures due to bad solder connections.
However, these can be easily repaired and do not effect the monitor's
heart - the CRT.  You wouldn't leave your TV on 24 hours a day, would you?

Also see the section: "Thernal cycling and component life".

Some of the newest ('green') monitors have energy conserving capabilities.
However, it is necessary for the software to trigger these power reduction or
power down modes.  Few monitors in actual use and fewer workstations or PCs
are set up to support these features.  If you have such a monitor and computer
to support it, by all means set up the necessary power off/power down timers.
However, using the power saving modes of a 'green' PC with an older monitor
can potentially cause damage since some of the modes disable the sync signals.
A 'green' monitor which can detect a blank screen and and use this as a trigger
can easily be used with a screen saver which can be set to display a blank
screen - on any PC or workstation.

Even if the monitor does not support power saving modes, a blank screen or
dark picture will reduce stress on the CRT and power supply.  Electronic
components will run cooler and last longer.

Please make it a habit to turn your monitors off at night.  This will extend
the life of the monitor (and your investment) and is good for the environment
as well.  For workstations, there are good reasons to leave the system unit
on all the time.  However, the monitor should be turned off using its power
switch.  For PCs, my recommendation is that the entire unit be turned off at
night since the boot process is very quick and PCs are generally not required
to be accessible over a network 24 hours a day.

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Written by Samuel M. Goldwasser. | [mailto]. The most recent version is available on the WWW server http://www.repairfaq.org/ [Copyright] [Disclaimer]