TV repair

Discussion in 'Technical Repair' started by EE_Bob, Jul 15, 2010.

  1. EE_Bob

    Thread Starter Member

    Jul 21, 2009
    16
    0
    I have a sony 27 inch tv whose front RCA jacks didn't function properly. The audio worked (right and left channels), but there was no video (well it would display if I put pressure on the yellow connector at a certain spot.

    I got a replacement part and spent the better half of the day desoldering the old av jacks and installing the new ones. The solder points looked fine and I didn't think swapping out the av jacks was going to do me much good. I however noticed after replacing the part that one of the solder pads was somewhat lifted. I don't know much about solder pads or how they connect to the underlying copper networks in pcb's but I could only assume that this was why I didn't have any video input (solder pad was directly connected to video rca jack).

    I end up taking some braided wire tinning the tips and soldering from the lifted solder pad to a resistor that was in series with the video trace on the pcb. I don't know for sure if the lifted pad would've made the proper connection or not but I didn't want to take my chances (video shows up fine now).

    So my question is, is it harmful to have 2 wires placed in parallel between 2 components? (Want to make sure that even if the raised solder pad is somehow making a connection to the video trace on the pcb that the addition of a 2nd connecting wire will not cause any problems).
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,646
    2,344
    Hello,

    Can you make a photo of waht you have done?
    That way we can see what you did and if it is OK.

    Bertus
     
  3. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,750
    759
    Thin wires will do just fine, but you have to know ur circuit first.
    Post a pic.
     
  4. windoze killa

    AAC Fanatic!

    Feb 23, 2006
    605
    24
    I would have to agree. So long as the length of the wire isn't excessive it will be fine. Having said that I would find the nearest pad away from the lifted one and scrape all the solder resist (the green enamel) of the copper track between the two pads. Once you have cleaned the track you can then tin the track and solder the wire along the track between the two pads. This process will ensure there are no stray pickups. It would be the nearest thing to a professional track replacement.
     
  5. tom66

    Senior Member

    May 9, 2009
    2,613
    213
    The resistor is most likely some kind of 75 ohm terminator or input resistor, so it should be fine to run a signal from the jack to the resistor.
     
  6. Harrington

    New Member

    Dec 19, 2009
    86
    3
    Might be an idea to get hold of a circuit diagram just to be on the safe side then you can double check that the through track doe sent belong to another part of the circuit Fly back blanking path or Frame stage in case you accidentally short the connectors to a High voltage rail typically this can be in the order of anything 250volts + that means that if you make a mistake and this gives someone an electric shock you could find yourself in deep water

    For your own good really that's all Not worth taking a chance with especially if you are going to plug this into another peace of kit It could prove harmful if you do

    Sensible advice !! Get A circuit diagram just in case better to be safe than sorry
     
  7. tom66

    Senior Member

    May 9, 2009
    2,613
    213
    A decent television design will keep the high voltage circuitry well away from the low voltage signal input, not only for safety but for picture quality, having a high noise source near the input jacks is a Bad Idea.
     
  8. EE_Bob

    Thread Starter Member

    Jul 21, 2009
    16
    0
    I can provide a simple circuit diagram. It comes from a service manual, however it does not belong specifically to my tv (sony kd27fs170 but I have a manual for a similarly built tv using the same chassis). I don't have access to the manual right now so I'll try to upload the schematic tomorrow. I have a hunch that tom66 is correct about the resistor. I measured with a multimeter before attaching the wire from the video jack (it read as 75 ohms).

    The video works just fine and I feel that the connection I made should be okay. My main question was what effect if any does having a second connection between the same two nodes produce?

    Thank you so far for the interest.
     
  9. windoze killa

    AAC Fanatic!

    Feb 23, 2006
    605
    24
    If the video is working fine the you have answered your own question. The two wires are not having any effect.
     
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