Figuring out a PC monitor's pinout - anyone?

Discussion in 'General Electronics Chat' started by u2020bullet, Mar 18, 2014.

  1. u2020bullet

    Thread Starter New Member

    Mar 18, 2014
    9
    1
    So i have this old LG Flatron F700B laying around, but my dog chewed up the VGA cable, which i cut off, bought a VGA connector and tried random pinout combinations on the internet, naturally, that didn't work. So does anyone have any experience with this? I'm still searching for the pinout online but it doesn't look very promising.
     
  2. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,866
    988
    Bad dog!

    You don't really need the VGA pinout. What you really need is the monitor service manual

    Try searching

    lg flatron f700b service manual pdf


    But those wires should be color coded. How badly was it chewed? You should be able to match the colors.
     
    u2020bullet likes this.
  3. u2020bullet

    Thread Starter New Member

    Mar 18, 2014
    9
    1
    I have acquired the service manual which doesn't seem to mention the cable at all. How exactly do i match the colors?
     
  4. shteii01

    AAC Fanatic!

    Feb 19, 2010
    3,373
    494
    Contact LG and ask.
     
  5. WBahn

    Moderator

    Mar 31, 2012
    17,715
    4,786
    You take the old cable end and use an ohmmeter or something else (a battery and flashlight bulb will work) and map out which color wire goes to which pin on the connector.

    You then wire the new connector so that the same color wire in the cable coming from the monitor goes to the same pin that that wire did in the old cable end.
     
    u2020bullet likes this.
  6. u2020bullet

    Thread Starter New Member

    Mar 18, 2014
    9
    1
    I just understood what spinnaker said, so right now i'm removing the insulation off the wires so i can splice and solder them back together. Hopefully this works, if not, i'll ask WBahn to explain the whole bulb and battery thing since i'm quite a newbie in the electronics world. :)
     
  7. Zerotolerance

    Member

    Sep 18, 2011
    56
    10
    Why not just buy a new VGA cable? They are generic and cheap. You can find one just about anywhere for free. Ask a friend, I'm sure they have a spare lying around. I know I have lots of them. Unless the cable is not detachable from the monitor end, which I assume this is the case, but you weren't very specific.

    All VGA pinouts are the same, so I dont see the problem here?
    1 - Red
    2 - Green
    3 - Blue
    5 - Ground
    13 - H-sync
    14 - V-sync

    All you need to do is pull back the shielding and it will expose the wires.

    If you cut off the VGA connector end just match the colors to the new one. Unless the dog chewed the wires off right exactly at the VGA connector.

    Pics of the chewed cord and wires with shielding pulled back would be nice if possible.
     
    Last edited: Mar 18, 2014
    u2020bullet likes this.
  8. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,669
    804
    Lots of old CRT monitors have the cable embedded and you cannot easily change it.
     
    u2020bullet likes this.
  9. u2020bullet

    Thread Starter New Member

    Mar 18, 2014
    9
    1
    The cable is in fact embedded in the monitor, otherwise i'd just plug in a different cable. :)
    I did splice and solder everything, the monitor does respond but the colors are messed up, and as soon as i move the cable even a little bit, the colors start playing around the screen, and i just can't understand why since everything is properly soldered, unless i accidentally nicked one of the cable threads. Would that cause a problem?

    @Zerotolerance: Are you sure about the pinout? Cause i've seen plenty of different ones online.
     
  10. Zerotolerance

    Member

    Sep 18, 2011
    56
    10
    People still use CRT monitors???????? :eek:

    The pinouts have to match that of the Video Card and every Video card has the same pinouts.

    Sounds to me like you may have nicked the insulation of one or some of the wires and the shielding/foil is grounding them when moving the cable around.
     
    u2020bullet likes this.
  11. u2020bullet

    Thread Starter New Member

    Mar 18, 2014
    9
    1
    Ok, i'll try to explain exactly what i did the best way i can.

    Stuff i had:
    The part of the cable coming out of the monitor, and the part of the cable i cut off (and re-cut again to remove the destroyed part of the cable that the dog chewed on).

    The cable (the one holding all other cables), had some aluminum foil and wires threaded around the foil (guessing those are just to make sure you can't over bend the cable thus damaging the insides), so i removed the aluminum foil and the wire around it to expose the cables inside, there was a blue one, a red one, and a green one and a transparent one (those are the colors of the really thick insulation on top of those 4 cables), next to those 4 cables, there were multiple other really thin cables, a black one, a white one, a yellow one, a purple one. Removed the insulation from all those cables, spliced them with the corresponding cables from the other piece of the cable, soldered each, wrapped each of them in electrical tape, melted the ends of the tape to make sure it's air-proof. So basically what i ended up with was a neat set of cables properly connected, but not very functional, yes the monitor does show the picture but the colors are all wrong and i get white horizontal lines.

    If any additional information is required, let me know and i will provide.

    PS: Yes we still use CRT monitors. :p I still have one connected to an IBM 300GL that i restored last year, but this is my first computer monitor so that's why i wanted to fix it. :)

    EDIT: And if you didn't understand something i wrote, please say so, so i can rephrase it. :)
     
    Last edited: Mar 18, 2014
  12. shteii01

    AAC Fanatic!

    Feb 19, 2010
    3,373
    494
    I am back to using my old Sony Trinitron 17" CRT because one capacitor broke on the power board of my 22" LCD.
     
  13. u2020bullet

    Thread Starter New Member

    Mar 18, 2014
    9
    1
    Ok, so it's a coax cable judging by my google search, didn't know that earlier, english is not my primary language so my apologies for any mistakes. :)
     
  14. Zerotolerance

    Member

    Sep 18, 2011
    56
    10
    I have repaired several LCD PSU's due to faulty caps. Darn things! u2020bullet please take a pic for us of the connector and wires exposed so that we can see what you did if possible.

    The smaller wires are your signal wires

    BTW, I never would have guessed english was not your first language :)

    What pins do you have the RGB wires connected to on the VGA connector?
     
    Last edited: Mar 18, 2014
    u2020bullet likes this.
  15. u2020bullet

    Thread Starter New Member

    Mar 18, 2014
    9
    1
    So since that didn't work and it wasn't exactly reversable (seeing as how i melted the ends on the electrical tape), i cut the connector off, tried to open it, and i guess someone in LG decided their cables should be unopenable, which means a busted VGA connector. Luckily i have 2 spare VGA connectors, but the problems is, i have no idea how to connect them, no pinout i found online shows exactly which wire goes where, so i'll just remove the insulation off the wire from the monitor, take a picture and post it here, and you guys might be able to tell me which to solder on what part of the connector. Picture incoming in a few minutes (just gotta re-strip the insulation).

    Photo: Sorry about the picture quality, my camera is empty so i had to take this one with a phone camera.
    As you can see, the thick green wire doesn't have anything wrapped around it like the red and the blue.

    [​IMG]
     
    Last edited: Mar 18, 2014
    Zerotolerance likes this.
  16. Zerotolerance

    Member

    Sep 18, 2011
    56
    10
  17. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,669
    804
    The schematic doesn´t seem to be too helpful in this matter. If your colours are still filckering when you move the cable, then I suggest you take a multimeter and find out which colours of the cable correspond to which pins on the vga connector, and which colours go wher inside the monitor. Then get a new vga cable, cut one end of, once again find the appropriate pins and match them and connect the wires to proper places inside the monitor.
     
    u2020bullet likes this.
  18. Zerotolerance

    Member

    Sep 18, 2011
    56
    10
    It will help if he breaks open his monitor and follows the traces. Then again I don't know his technical ability or ability to read a schematic. :confused::cool:

    I suggest buying a VGA cable with the VGA connector already on the end and unsolder the traces inside the monitor and solder the new cable to the inside of the monitor. That's your best bet it seems with your technical ability ??? IDK

    kubeek sorry didnt read your entire post. I assume you are saying the same thing?
     
    u2020bullet likes this.
  19. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,669
    804
    Yes I was trying to say the same thing, but the schematic doesn´t show colours of wires and it will not be too easy to trace the signals from the chips if you dont have enough experince, so I was trying to show how to work out what goes where just from the old cable. Not too sure how inteligible it was though ;)
     
    u2020bullet likes this.
  20. WBahn

    Moderator

    Mar 31, 2012
    17,715
    4,786
    The signals are going to be pretty sensitive to EMI since they have about a 100MHz bandwidth. So even if your patch job didn't have any DC faults (and it might have -- you should have ohmed it out (checked continuity, including cross-continuity) as you went, your problems could be due to cross talk and EMI pick-up. Is the ferrite coil still in place, or was it on the part of the cable that got chewed?
     
    u2020bullet likes this.
Loading...