monitor won't display

  • Thread starter Thread starter Rory Deol
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Rory Deol

I purchased an eMachines W2040 for $10. As it turns out it won't
display video. I can boot it up (I think) but the monitor receives no
signal. I tried a different monitor and still no signal. Then I
noticed that the original eMachines monitor has the #9 pin missing. I
am wondering if this broke off in the connector on the motherboard and
was then forced into the slot by my trying a different monitor with a
# 9 pin in place. Could there be another easily solved answer to this
problem? If I have to replace the motherboard what would be a
compatible one? The video is integrated if that helps. Any help would
be greatly appreciated.
 
Rory said:
I purchased an eMachines W2040 for $10. As it turns out it won't
display video. I can boot it up (I think) but the monitor receives no
signal. I tried a different monitor and still no signal. Then I
noticed that the original eMachines monitor has the #9 pin missing. I
am wondering if this broke off in the connector on the motherboard and
was then forced into the slot by my trying a different monitor with a
# 9 pin in place. Could there be another easily solved answer to this
problem? If I have to replace the motherboard what would be a
compatible one? The video is integrated if that helps. Any help would
be greatly appreciated.
Click to expand...

I wasn't able to find a nice tutorial, and only found scraps.

The history of VGA is kinda recorded here. It looks like originally,
resolution info was signaled by static ID pins. At some point, the VESA DDC
added the ability for the host to read the monitor's characteristics,
via a serial interface. Inside a modern monitor, there is a serial EEPROM,
with an I2C interface (serial clock and data). Pin 9 is supposed to be
a source of +5V, flowing from the host to the monitor, giving one
milliamp to read the serial EEPROM.

http://www.epanorama.net/documents/pc/vga_bd15.html

So, when a video cable is missing pin 9, the cable would be from
another era, before DDC/EDID. It means the host cannot determine
the resolution options of the monitor, at startup, if the monitor
is turned off. Presumably, once the monitor is turned on, it
could supply its own +5V. And of course, if the monitor does not
support DDC, the computer can send all the clock signals it wants
on the DDC interface, and there would be no answer.

The computer could try to put out 640x480, assuming it has detected
that a cable is connected to the RGBHV (red, green, blue,
horizontal_sync, vertical_sync) signals. So I would not necessarily
conclude, that because pin 9 (key) is missing, that it is a broken
pin. It could mean the monitor is pre-DDC, and does not support the
DDC function. But computer systems still have to support such
monitors, and missing pin 9 should not prevent the setup from
working.

My old CRT (Sony Trinitron) had an RGBHV coaxial interface, and
an RGBHV to VGA adapter cable. So that monitor would not have had
any fancy DDC on it, and it still worked with the computers I plugged
it into. I believe I've even used that monitor on the computer I'm
typing on, when I built this computer.

This would be the modern definiton of the pins:

http://www.hardwarebook.info/VGA_(VESA_DDC)

This pinout is a mix of the old and new. Here is an example
of mention of pin 9 being "missing" and used as a key. (I.e. Not
likely to have just broken off, but done on purpose.)

http://www.cabletechguide.com/Technical Articles/VGA Pinouts.htm

This is a standards body for computer display output -

http://www.vesa.org/FAQ/standardsFAQ.htm#DDC1

Hope that helps somewhat,
Paul
 
Rory Deol said:
I purchased an eMachines W2040 for $10. As it turns out it won't
display video. I can boot it up (I think) but the monitor receives no
signal. I tried a different monitor and still no signal. Then I
noticed that the original eMachines monitor has the #9 pin missing. I
am wondering if this broke off in the connector on the motherboard and
was then forced into the slot by my trying a different monitor with a
# 9 pin in place. Could there be another easily solved answer to this
problem? If I have to replace the motherboard what would be a
compatible one? The video is integrated if that helps. Any help would
be greatly appreciated.
Click to expand...
Google is your friend! "vga pinout" shows pin 9 not used.Now you know
why it was $10! To troubleshoot, disconnect ALL cables and adapters and
memory. Fans should run and continuous series of beeps. If not, is PSU, CPU
or motherboard.

Mike.
 
Google is your friend! "vga pinout" shows pin 9 not used.Now you know
why it was $10! To troubleshoot, disconnect ALL cables and adapters and
memory. Fans should run and continuous series of beeps. If not, is PSU, CPU
or motherboard.

Mike.
Click to expand...

Fans run fine but no beeps. Does that give any clue as to what it
might be?
 
Rory Deol said:
Fans run fine but no beeps. Does that give any clue as to what it
might be?
Click to expand...
If you can borrow a PSU to test it? The only way to ID is to test with
known good parts. Ask how much a local computer shop would charge to test
parts.

Mike.
 
In alt.comp.hardware.pc-homebuilt Rory Deol said:
Fans run fine but no beeps. Does that give any clue as to what it
might be?
Click to expand...

To beep, you need a speaker attached.
(They have *tiny* speaker-replacement transducers these days.)
Has to be hooked across the speaker-pins on the motherboard.
 
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