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Bush Tv (CRT) having horizontal lines on the top half of TV

Discussion in 'General Electronics Discussion' started by ramniwassingh0, Oct 26, 2013.

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  1. ramniwassingh0

    ramniwassingh0

    2
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    Oct 26, 2013
    Hi Members,

    Can anybody help me. I have a Bush TV purchased in 2001. For past 2 weeks it is giving me problems. It is showing horizontal lines on top half of the screen. the picture is also zoomed up from top part of the pictures on TV. Sometimes it gives a mirror image on the top part of screen. i am totally confused:confused:

    what may the reason for this. What can be done to sort out the issue.

    Shout back if you need more info.

    thanks,
    Ram
     
  2. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    I would say it has a vertical sync problem. Not that that is going to help any.

    Bob
     
  3. davenn

    davenn Moderator

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    Sep 5, 2009
    hi ram
    welcome to the forums

    is this a CRT older type or a plasma/LED/LCD ie a more modern type screen?

    if its an older CRT type, flyback ( retrace) lines is a pretty common fault
    do some googling on your make and model with a retrace lines fault

    Dave
     
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
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    Nov 28, 2011
    On CRT TVs, vertical deflection problems including retrace lines are often caused by failing electrolytics in the frame output (vertical deflection) circuit.

    Have a look at Sam Goldwasser's excellent Repair FAQ on TV sets:
    http://www.repairfaq.org/samnew/tvfaq.htm
    It's seven years old now, but still mostly relevant and very thorough.

    READ THE SAFETY SECTIONS!

    Read the general information. This should tell you how to locate the frame circuitry. A simple way is to follow the wires from the deflection yoke; two of them go to the line circuitry, near the flyback transformer. The other two go to the frame circuitry.

    Under Deflection Problems, there's a section called Vertical Squashed, but it doesn't help much. Once you've identified the frame output section, look for bulging or leaking electrolytic capacitors, or just replace them all on suspicion.

    The problem could also be a faulty frame output IC or a problem with a supply rail to the frame stage, but replacing the electrolytics is a quick simple job and likely to fix the problem.
     
  5. ramniwassingh0

    ramniwassingh0

    2
    0
    Oct 26, 2013
    @ davenn: Its an old CRT type Tv. I am still trying to find out the flyback retrace lines.not sure how to identify it?

    @KrisBlueNZL: I did try to check the any bulging or leaking electrolytic capacitors, but to my dismay there wasn't any sign of these on the capacitors.

    The thing is the problem is not a permanent one. whenever this (picture zooming in on top half of TV/ picture bouncing/reverse image/picture fold on top half of screen) happens then, if I tab the TV a little on top or side, then it automatically comes back to original picture shape, but eventually goes after remaining normal for a random time. Sometimes picture remains normal after tap for 10-15 mins sometimes even hours.

    Is it happening due to some dead capacitor, or is there any broken links anywhere in the circuitry? how can I identify which part of circuit I have to look into? when I observe the circuit i can see that some of components are in 2XX, 3XX, 4XX series etc.. Can you tell me which series of components should I check? If there are no visible bulging or leaking in capacitor how should I identify that particular capacitor is dead and needs replacement?

    Any kind of help and suggestions will help me a lot in sorting out this problem.
     
  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    If tapping the set makes the problem come and go, that sounds like a bad connection of some kind, such as a dry joint. Have a close look at the solder joints all around the board and solder up anything that looks suspect. (Leave the set unplugged for at least ten minutes first.)

    I explained how to find the frame output section in my previous post. Read the FAQ I linked to; it contains important safety information and general information about the major parts of a TV set that you will need to know.
     
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