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Mains interferance on new LCD - help

  • 22-12-2007 6:38pm
    #1
    trackerman
    Registered Users, Registered Users 2 Posts: 519 ✭✭✭


    I just installed a new Sony LCD, it's great but I'm getting what appears to be mains interfreance.

    It appears as a 1' band of ripple that slowly works it's way up (sometimes down) the screen. The 1" band slightly distorts the image as it passed, making it slightly darker.

    Reason I think it's mains is that it gets worse when I turn on my christmas tree lights!!!

    Moving the TV to another room does not help.

    The cable signal is NTL basic package and seems to be perfect on my old tube TV.

    I've added several "extension" TV points around the house, these are not NTL installed and I used the standard co-ax outlet points from B&Q.

    Could these additional TV points be picking up mains "hum" and carrying it ti my TV?

    Is there a filter I cab get for this problem ?

    Thanks in advance guys.

    Ray


Comments

  • #2
    byte
    Moderators, Regional North West Moderators Posts: 19,158 Mod ✭✭✭✭byte
    byte


    Yeah, you'd need an isolator. I thought that cableco's used these anyway on the incoming cable where it enters the house, where the isolator also doubles up as an FM/TV diplexer.


  • #3
    John1000
    Closed Accounts Posts: 41 ✭John1000


    Could be your scart cable. An poorly shielded scart cable will give a 1" band
    slowly moving down the screen and you would also be able to see the faint outline of another channel on the tv.


  • #4
    trackerman
    Registered Users, Registered Users 2 Posts: 519 ✭✭✭trackerman


    Thanks for the suggestions guys...

    It's probably not the SCART since I'm not using one.

    But I'm intrested in the isolater theroy.
    Only one of my TV points has the FM/TV type socket, it was installed by NTL.
    All the others are very cheap single socket types that don't have any filters built in. These are fed from a splitter that I installed in the NTL box outside my house (the white box next to the gas box).
    I think this is responsible for my problems.

    Any suggestions on where I can get good quality splitter and TV outlet points in Dublin?


    Thanks.


  • #5
    byte
    Moderators, Regional North West Moderators Posts: 19,158 Mod ✭✭✭✭byte
    byte


    Do you have the hum on the TV that has the FM/TV diplexer?

    Maybe move it out to where your splitter is. So that NTL comes into the FM/TV diplexer (hopefully an isolator also), and from that into your splitter feeding the rooms.


  • #6
    trackerman
    Registered Users, Registered Users 2 Posts: 519 ✭✭✭trackerman


    Good suggestion Byte, I'll try that.

    Happy Christmas ;)

    Trackerman.


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  • #7
    Antenna
    Registered Users, Registered Users 2 Posts: 2,358 ✭✭✭Antenna


    trackerman wrote: »
    I just installed a new Sony LCD, it's great but I'm getting what appears to be mains interfreance.

    It appears as a 1' band of ripple that slowly works it's way up (sometimes down) the screen. The 1" band slightly distorts the image as it passed, making it slightly darker.Ray

    What about a VCR RF output, is that affected??

    interesting comment about the christmas lights, instead of the lights try plugging in something with a heavier load, like an electric heater or a kettle instead?? does that make it worse? - I'm just wondering might the mains voltage reaching the TV be a bit low?


  • #8
    gerryo
    Registered Users, Registered Users 2 Posts: 498 ✭✭gerryo


    Antenna wrote: »
    What about a VCR RF output, is that affected??

    That a good idea, also check with a DVD player (scart connection) & unplug the NTL connection while you check.
    Antenna wrote: »
    interesting comment about the christmas lights, instead of the lights try plugging in something with a heavier load, like an electric heater or a kettle instead?? does that make it worse? - I'm just wondering might the mains voltage reaching the TV be a bit low?

    Yeah, it does sound like the mains is very low, or else the TV PSU is not working correctly. Last time I saw problems like this, it was bad PSU on a monitor. Also, microwave ovens can do this, so can electric motors, etc.

    If you get still get the problem with a DVD player, then check your plug wiring - is the fuse loose, getting hot?

    Try it in someon else's house for a quick go/no go test!


  • #9
    trackerman
    Registered Users, Registered Users 2 Posts: 519 ✭✭✭trackerman


    I've been un-plugging and plugging most of my household appliances to see which makes a difference, so many that I've lost track.

    Now the image seems almost perfect, it's only RTE 1 that has any detectable interferance (not the same as before), it's wide vertival band of light grain that moves form left to right, but it's very hard to see.

    So I'm not quite sure how I cured it, but it's a hell of a lot better now!!!

    I suspect thare may have been a dirty earth connect on one of the plugs and simply re-plugging it cleaned the connection.

    Thanks for te help guys.


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