CRT Monitor and Y-Splitter Issue

M

MapleE.

Hi:
I hooked up 'Y Monitor Splitter' back of PC in order to get two different
monitors, one for LCD and another for CRT/older monitor.

On CRT monitor, picture along with words are both distorted and very fazy as
if I'm looking at a half-broken monitor, while LCD is clear and crisp to
touch.
Once un-hook 'Y-Splitter' from back of PC, the CRT Monitor is in perfect
shape, ... deep and rich colored picture, for that I've been still keeping
an older CRT.

It seems to me that the CRT is NOT capable to deal and handle with this, a
new device 'Y-Splitter,' unlike the LCD.

My question is;
Is there anyway for me to correct this, ... picture and words distortion and
faziness?
Or, is there a cleaver device similar to 'Y-Splitter' in order to able to
use two monitor, particularly for CRT?

Thanks for your help in advance.
 
B

BillW50

In MapleE. typed on Thu, 15 Oct 2009 16:36:12 -0400:
Hi:
I hooked up 'Y Monitor Splitter' back of PC in order to get two
different monitors, one for LCD and another for CRT/older monitor.

On CRT monitor, picture along with words are both distorted and very
fazy as if I'm looking at a half-broken monitor, while LCD is clear
and crisp to touch.
Once un-hook 'Y-Splitter' from back of PC, the CRT Monitor is in
perfect shape, ... deep and rich colored picture, for that I've been
still keeping an older CRT.

It seems to me that the CRT is NOT capable to deal and handle with
this, a new device 'Y-Splitter,' unlike the LCD.

My question is;
Is there anyway for me to correct this, ... picture and words
distortion and faziness?
Or, is there a cleaver device similar to 'Y-Splitter' in order to
able to use two monitor, particularly for CRT?

Thanks for your help in advance.

Sounds like an impedance/loading problem to me. And I am not sure why
you would want the same display at two places. Unless it is for a
presentation or something. And if I am correct, you can ruin your video
card. As you can ruin the output drivers on the card. It is probably
rare, but can happen.
 
I

Ian D

MapleE. said:
Hi:
I hooked up 'Y Monitor Splitter' back of PC in order to get two different
monitors, one for LCD and another for CRT/older monitor.

On CRT monitor, picture along with words are both distorted and very fazy
as if I'm looking at a half-broken monitor, while LCD is clear and crisp
to touch.
Once un-hook 'Y-Splitter' from back of PC, the CRT Monitor is in perfect
shape, ... deep and rich colored picture, for that I've been still keeping
an older CRT.

It seems to me that the CRT is NOT capable to deal and handle with this, a
new device 'Y-Splitter,' unlike the LCD.

My question is;
Is there anyway for me to correct this, ... picture and words distortion
and faziness?
Or, is there a cleaver device similar to 'Y-Splitter' in order to able to
use two monitor, particularly for CRT?

Thanks for your help in advance.

Having two monitors in parallel on the same video output
is loading the video card, and dropping the signal level to
below what is required for the CRT. The LCD is more
tolerant of low video signal levels. If you want to display
on two monitors, you need a dual output video card, or
an amplified video splitter.
 
B

Bob Knowlden

Aside from the analog considerations mentioned by other posters, note that
some modern graphics cards require DDC handshaking with the monitor.

http://en.wikipedia.org/wiki/Display_Data_Channel

I doubt that would work with a simple splitter.

You probably want a graphics card with dual outputs. You may even be able to
run both monitors at optimal resolutions. (The LCD monitor may have a fixed
60Hz refresh rate. That gives too much flicker with a CRT, at least for me.)

Good luck.
 
P

Paul

Ian said:
Having two monitors in parallel on the same video output
is loading the video card, and dropping the signal level to
below what is required for the CRT. The LCD is more
tolerant of low video signal levels. If you want to display
on two monitors, you need a dual output video card, or
an amplified video splitter.

This video amplifier with two outputs is $139. A video card
with two output connectors, can be purchased for less money
than this.

http://www.lenexpo-electronics.com/...ibution-Amplifier-with-Local-Out-p-17880.html

VGA uses coaxial connectors and controlled impedance transmission.
(At least is does for RGB, but may not for H and V sync signals.)
A single video cable has 75 ohm impedance coax inside. The
display device (CRT or LCD) has 75 ohm termination resistors
at the end of the line, for RGB.

If you passively split, by just wiring two cables from one point,
like this, there will be signal reflections from the junction,
as there is now an impedance mismatch. That causes a fuzzy picture.

/
____/
\
\

It is also possible to wire up a "resistive splitter". That is a
configuration of resistors, one set per color signal (RGB), that
maintains the impedance seen looking into that arm of the line. That
solves the impedance matching problem, so there are no reflections.
But that does affect the signal amplitude (basically, you "can't get
something for nothing", electrically speaking). VGA signals would be
sensitive to such a treatment. (This is the first link I could
find, but this isn't exactly what I had in mind. Still, it
illustrates the concept of a resistive splitter.)

http://www.microwaves101.com/encyclopedia/Resistive_splitter2.cfm

"where attenuation is not an issue"

The Lenexpo amplified box above, solves all the problems. If you go to a
big box computer store, where a dozen LCD monitors are displaying
the same signal content, look under the counter. You'll see a
video distribution amplifier with multiple outputs. That is how
they do it at the computer store. Distribution amplifiers for VGA
can have anywhere from two to sixteen outputs. And you can also
concatenate them, for more outputs if you want (with some potential
degradation eventually, in sharpness). My big box computer store,
actually had two eight channel amps, tied together to give 15 outputs.

The components inside the amplified box, should not be that
expensive, so you may be able to get a better price than $139.
You can see, just how horrible a concept can be used for an
amplified design, here. Hopefully, the above box for $139,
doesn't do it this way. Note the suggested VGA resolution for
this design.

http://www.epanorama.net/zen_schematics/Circuits/Misc/monitor.html

Using a PCI card with two connectors, really is smarter. There
can be other problems with the distribution amp concept, in
terms of the handling of DDC/EDID and the like. When a single
monitor is connected to a video card, the serial DDC interface
is how the computer gets resolution choice information from
the monitor. Inserting a VGA distribution amp, may break
the path to the DDC signal. There are ways to fix that,
like a Gefen box with EEPROM chip inside, but that only adds
to the cost of the solution. It is hard to predict, how any
video distribution amp, will handle signals other than RGBHV
on the connector. It could, for example, wire all the signals
through to the "loop" connector, in which case one of the
monitors would be connected to that connector. So there are
details that could make the eventual project cost, higher.

Pin 12 and 15, are used for DDC serial communications. A
distribution amp, may be primarily concerned with
getting RGBHV correct, but not pass through the
DDC signals. The video card driver uses that,
to enable some of the higher output resolutions.

http://en.wikipedia.org/wiki/VGA_connector

Paul
 

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