VGA Challenge

Discussion in 'General Electronics Chat' started by dannybeckett, May 23, 2010.

  1. dannybeckett

    Thread Starter Active Member

    Dec 9, 2009
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    Hi guys.

    I have a flatscreen monitor with a VGA output. The VGA cable, monitor side, is connected to the monitor via header on the monitor motherboard (no VGA socket. The other end of the cable has been snipped. I would like to buy a new vga cable and splice them together - but the colour of wires are not universal.

    Is there any way, using a function generator, oscilloscope and multimeter, that I can find out what cable does what (so I know how to splice the new end on)? I know where 6 of the wires go - red analog, green analog, blue analog and their respective returns - they are easily identified by their colour (only bit which is universal) and the fact they have a ground sheath around them.

    Heres a pinout for VGA

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

    Any help is massively appreciated

    Dan
     
  2. dannybeckett

    Thread Starter Active Member

    Dec 9, 2009
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  3. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    so how are you doing?
     
  4. dannybeckett

    Thread Starter Active Member

    Dec 9, 2009
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    I still need a way of identifying what wire has what function coming from the monitor, bar the 6 I have mentioned
     
  5. jamjes

    Member

    May 10, 2010
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  6. dannybeckett

    Thread Starter Active Member

    Dec 9, 2009
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    ahh excellent. yeah it works natively at 1024x768. how do i go about identifying h and v sync?
     
  7. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    What is the brand and type number of the monitor?
    Perhaps there is a schematic for it.

    Bertus
     
  8. rjenkins

    AAC Fanatic!

    Nov 6, 2005
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    Are there any other cores that are screened, or using twisted pairs?

    How many other none-ground signals are there?
     
  9. dannybeckett

    Thread Starter Active Member

    Dec 9, 2009
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    @ bertus - its a GNR F153. its pretty old. the circuitboard that the vga cable connects to is "LCT-M 94V-0"

    @ rjenkins - nothing else is twisted or screened. I have attached pics so you can see the wires themselves. the 3 thick ones are the screened analog RGB cables. Im not sure which other ones are grounds

    Thanks again guys
     
  10. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    I could only find a specsheet at the moment:

    Max. Resolution
    XGA 1024 x 768

    Scan Frequency
    Horizontal: 30kHz - 60kHz
    Vertical: 50Hz - 75Hz

    Bertus
     
  11. dannybeckett

    Thread Starter Active Member

    Dec 9, 2009
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    im guessing that frequency comes from the graphics card and not the monitor?
     
  12. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Yes, the two frequencies come from the videocard.
    In the old days with a CRT monitor those where the scanspeeds of the trace.

    In LCD monitors the frequencies are used to derive to dot speed and the dot position.

    Bertus
     
  13. dannybeckett

    Thread Starter Active Member

    Dec 9, 2009
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    ahhh i see. can we use this info to identify any other wires?
     
  14. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Do you have the rest of the cable?
    (the piece that was cut off).

    When you connect this to a video card you could measure the signals with an oscilloscope.

    Bertus
     
  15. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Are u up to this. If so find some heat shrink sleeving that fit's those wires or some insulation tape and find a way to solder. I can guide you the connection with my eyes closed. Hopefully
     
  16. dannybeckett

    Thread Starter Active Member

    Dec 9, 2009
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    Unfortunately bertus I dont have the rest of the cable - if i did i could use a multimeter to check and see what wire goes where =[

    R!f@@ I am good with electronics, I can solder well. I have plenty of insulation tape. All I need to know is how I can find out the purpose of each wire coming from the monitor so I can splice a new end onto it. Ive checked the pinout of the genesis gmZAN2 chip and found vsync and hsync, but I cannot find continuity between those pins and any of the VGA wires which is odd.
     
  17. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    the picture shows which wire. Show what you wanna do and what have clearly
     
  18. dannybeckett

    Thread Starter Active Member

    Dec 9, 2009
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    The wire in the picture is the end of the monitor cable. I will draw a diagram of what I need to do. I hope this helps.
     
  19. dannybeckett

    Thread Starter Active Member

    Dec 9, 2009
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    so i need some way to determine the functions of those wires.
     
  20. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    OK that's good. Now show me the connection where the VGA cable terminates at the monitor ckt board
     
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