Damaging computer monitor with wrong input?

[[email protected]]

I'm working on an output circuit from a computer which outputs two
different kind of signals according to which mode it is set to (colour
low/medium resolution or monochrome high-resolution):

Mono mode : 35.70 KHz horizontal, 71.2 Hz vertical
Colour mode: 15.75 KHz horizontal, 50-60 Hz vertical

Is it possible to damage a monitor if it receives signals outside of
its intended range?

 

[Gibbo]

I'm working on an output circuit from a computer which outputs two
different kind of signals according to which mode it is set to (colour
low/medium resolution or monochrome high-resolution):

Mono mode : 35.70 KHz horizontal, 71.2 Hz vertical
Colour mode: 15.75 KHz horizontal, 50-60 Hz vertical

Is it possible to damage a monitor if it receives signals outside of
its intended range?

I think I am right in saying that older monitors would sometimes fail
(often with a bang) if fed an input with too high a line frequency.
Later monitors simply either ignore it or shutdown.

So it depends on your monitor.

 

[Baron]

I'm working on an output circuit from a computer which outputs two
different kind of signals according to which mode it is set to
(colour low/medium resolution or monochrome high-resolution):

Mono mode : 35.70 KHz horizontal, 71.2 Hz vertical
Colour mode: 15.75 KHz horizontal, 50-60 Hz vertical

Is it possible to damage a monitor if it receives signals outside of
its intended range?

Short answer ! Yes. Most modern monitors are intelligent enough to
recognise an out of range signal and display an error message! Older
ones are not !

 

[[email protected]]

[email protected] wrote:


I think I am right in saying that older monitors would sometimes fail
(often with a bang) if fed an input with too high a line frequency.
Later monitors simply either ignore it or shutdown.

So it depends on your monitor.

That's good and bad news.
The computer is an Atari ST and I intend to make it work with both the
custom Atari monitors and normal VGA monitors. Sounds like it could be
risky business to connect the Atari monitors (the Atari ST is a mid
80s - early 90s computer) to the new output without first making sure
the mode is correct for that monitor.
When you say they often go out with a bang -is that permanent failure
(as in throw it away, the CRT and everything is gone), or is it "just"
a matter of replacing some components around the signal input stage?
Anything that can be done to prevent this (in case I or someone
selects the wrong mode for the connected monitor)?

Regarding modern monitors I've heard that it's hard to find ones that
can handle the colour mode of 15.75 KHz horizontal rate -is this true,
or is it now common for monitors to be able to handle both my output
modes?

 

[Michael A. Terrell]

That's good and bad news.
The computer is an Atari ST and I intend to make it work with both the
custom Atari monitors and normal VGA monitors. Sounds like it could be
risky business to connect the Atari monitors (the Atari ST is a mid
80s - early 90s computer) to the new output without first making sure
the mode is correct for that monitor.
When you say they often go out with a bang -is that permanent failure
(as in throw it away, the CRT and everything is gone), or is it "just"
a matter of replacing some components around the signal input stage?
Anything that can be done to prevent this (in case I or someone
selects the wrong mode for the connected monitor)?

Regarding modern monitors I've heard that it's hard to find ones that
can handle the colour mode of 15.75 KHz horizontal rate -is this true,
or is it now common for monitors to be able to handle both my output
modes?

The flyback transformers went up in flames. The original monochrome
monitor for the IBM PC would burn if it was powered up without video
drive. That is why the power supply had the switched outlet than lasted
till the ATX format arrived.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Gibbo]

That's good and bad news.
The computer is an Atari ST and I intend to make it work with both the
custom Atari monitors and normal VGA monitors. Sounds like it could be
risky business to connect the Atari monitors (the Atari ST is a mid
80s - early 90s computer) to the new output without first making sure
the mode is correct for that monitor.
When you say they often go out with a bang -is that permanent failure
(as in throw it away, the CRT and everything is gone), or is it "just"
a matter of replacing some components around the signal input stage?

Usually trivial things like the output transistor and associated
components Repairable...... if you know what you're doing, but not
trivial.

Anything that can be done to prevent this (in case I or someone
selects the wrong mode for the connected monitor)?

I'm not sure about this but I don't think you can swap modes on the ST
without switching it off and back on again. At boot up it looks at the
13 pin socket to see if it has the "special" monitor attatched, if it
does, then it fires up in hi res mode.

Regarding modern monitors I've heard that it's hard to find ones that
can handle the colour mode of 15.75 KHz horizontal rate -is this true,
or is it now common for monitors to be able to handle both my output
modes?

The standard colour output of the Atari ST is bog standard European TV
line frequency. There were *millions* of monitors made with the same
standard that are now worth about nothing each. Car boot sales are full
of them. It will work into a scart input on a normal UK TV

 

[Stanislaw Flatto]

I'm working on an output circuit from a computer which outputs two
different kind of signals according to which mode it is set to (colour
low/medium resolution or monochrome high-resolution):

Is it possible to damage a monitor if it receives signals outside of
its intended range?

YES. As I learned by ordering the Linux OS to display on a monitor
selected by me horizontal and vertical frequencies.
The video card responded.
The lesson ended when a little puff of smoke emerged from the monitor
telling me that this monitor(RIP) was not up to this resolution.
"We always learn!" - a Hassidic proverb.

HTH

Stanislaw
Slack user from Ulladulla.

 

[jasen]

That's good and bad news.
The computer is an Atari ST and I intend to make it work with both the
custom Atari monitors and normal VGA monitors. Sounds like it could be
risky business to connect the Atari monitors (the Atari ST is a mid
80s - early 90s computer) to the new output without first making sure
the mode is correct for that monitor.
When you say they often go out with a bang -is that permanent failure
(as in throw it away, the CRT and everything is gone), or is it "just"
a matter of replacing some components around the signal input stage?
Anything that can be done to prevent this (in case I or someone
selects the wrong mode for the connected monitor)?

I would expect the transitor that drives the horizontal output
transformer. and possibly a few other parts near it and the main
fuse for the monitor.

if you could double the horizontal scan rate on your colour mode that
would put it within in range of VGA monitors. this is what VGA cards do
in "CGA emulation" mode each scan-line is sent twice.

another option would be a Y connector with a relay (or other circuit)
driven by a frequency detector so that it only connects the sync lines
to the apropriate monitor if it sees the right frequency.

vga monitors will shut down in the absense of sync.

Regarding modern monitors I've heard that it's hard to find ones that
can handle the colour mode of 15.75 KHz horizontal rate -is this true,
or is it now common for monitors to be able to handle both my output
modes?

you may have luck with LCD monitors that support video input.
try a place that has a satisfaction guarantee....