Monitor VGA connector question?

  • Thread starter Thread starter Bob
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B

Bob

Hi,

Does anyone know how an LCD monitor using a 15-pins VGA cable can tell if
the cable is plugged into a powered down machine and not plugged in at all?

Thanks.

Bob
 
Bob said:
Hi,

Does anyone know how an LCD monitor using a 15-pins VGA cable can tell if
the cable is plugged into a powered down machine and not plugged in at
all?

Thanks.

Bob
Click to expand...
There will be some resistance between various pins when its plugged into a
machine (even when its switched off). This is why if you unplug the monitor
while its powered on generally some sort of pattern or wording will apear to
incate no signal is available. What is it you want to do?

Paul
 
Bob said:
Hi,

Does anyone know how an LCD monitor using a 15-pins VGA cable can tell if
the cable is plugged into a powered down machine and not plugged in at all?

Thanks.

Bob
Click to expand...

I don't know about LCD monitors, but CRTs use the horizontal sync pulse
to determine if there is source data to be shown. I would think it
would be the same.
 
Thanks Paul, do you know which pins?

Yes on some monitor it goes into sleep mode if it is not connected to
anything (like an Acer AL1715) on LG1750SQ, it will display 'Check Signal
Cable' for ever.

Do you know if some video card may have different impedance?

Bob
 
Bob said:
Thanks Paul, do you know which pins?

Yes on some monitor it goes into sleep mode if it is not connected to
anything (like an Acer AL1715) on LG1750SQ, it will display 'Check Signal
Cable' for ever.

Do you know if some video card may have different impedance?

Bob
Click to expand...
I dont know but I'm sure a quick search with Google will yield results. The
question has to be what do you need to know for - what's the problem?

Paul
 
Did that and found the pinouts for VGA cable but nothing to tell me which
pins are used to detect disconnections.

It is an intriguing problem to satisfy my curiosity.

I have a LG1750SQ plugged into a ATI 9200se card running XP. When the XP is
powered down or XP shuts down monitor on power save mode, the monitor
displays a 'Check Signal Cable' and annoyingly showing this forever.

Plug this monitor into a similar machine with newer version the same card or
in a totally different card or different computer (tried two separate ones),
it behaves properly and goes into sleep mode properly.

Plug a Acer 1715 into my machine, it sleeps properly while the LG wouldn't.

So I am just curious to work out if on my card a couple of pins much be
presented to the monitor like an open circuit when the card goes into sleep
or being powered down. This is the same symptom exhibit when the cable is
pull out of the card.

To me, the monitor should goes into sleep after complaining for a few
seconds - like the Acer does.

I doubt it is a faulty monitor and more like a faulty video card.

Any suggestions?

Bob
 
Check your ACPI settings in your BIOS.

Bob said:
Did that and found the pinouts for VGA cable but nothing to tell me which
pins are used to detect disconnections.
Click to expand...

<snip>
 
Bob said:
Did that and found the pinouts for VGA cable but nothing to tell me which
pins are used to detect disconnections.

It is an intriguing problem to satisfy my curiosity.

I have a LG1750SQ plugged into a ATI 9200se card running XP. When the XP
is powered down or XP shuts down monitor on power save mode, the monitor
displays a 'Check Signal Cable' and annoyingly showing this forever.

Plug this monitor into a similar machine with newer version the same card
or in a totally different card or different computer (tried two separate
ones), it behaves properly and goes into sleep mode properly.

Plug a Acer 1715 into my machine, it sleeps properly while the LG
wouldn't.

So I am just curious to work out if on my card a couple of pins much be
presented to the monitor like an open circuit when the card goes into
sleep or being powered down. This is the same symptom exhibit when the
cable is pull out of the card.

To me, the monitor should goes into sleep after complaining for a few
seconds - like the Acer does.

I doubt it is a faulty monitor and more like a faulty video card.

Any suggestions?

Bob
Click to expand...

Absolutely - if you contact the graphics card supplier they may have a BIOS
upgrade for the card (or replace it with a newer model under the warranty)
if you advise them of this problem. You're right in that your juggling
around of components would tend to indicate a problem with this card.

Paul
 
Noozer said:
Check your ACPI settings in your BIOS.
Click to expand...
OK. But everything works perfectly except this monitor. Same ACPI setting in
the other machine that the LG works.
 
Absolutely - if you contact the graphics card supplier they may have a
BIOS upgrade for the card (or replace it with a newer model under the
warranty) if you advise them of this problem. You're right in that your
juggling around of components would tend to indicate a problem with this
card.
Click to expand...
Thanks Paul for your help.

I guess my son is happy with a faster LCD, to play game, and I am happy with
an LCD that sleeps properly on my box. I may as well let the sleeping dog
(LCD in this case) lie and will get a new video card when I feel like it.
 
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