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Louie
Louie, Technician
Category: TV
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Experience:  25+ yrs. experience in the field and 5+ yrs. online, down to component level.
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TV has a horizontal blue line across the middle of the screen.

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TV has a horizontal blue line across the middle of the screen. No picture, audio or any other sign of life from the TV, regardless of source.

The TV is a flat screen CRT, not LCD.
Hi and welcome to JustAnswer,

Initially, the horizontal line on a conventional/CRT type TV would indicate a failure of the vertical deflection circuitry. That there is no sound also would further point to a possible fault in the B+ supply fro the audio amp.

Offhand, try thumping on the side of the TV. If the horizontal line flickers or expand even just a little / even momentarily, then possibly a cold solder condition on any of the pins of the Vertical Output. It is also possible for the Vert + supply from the FBT (flyback transfoermer) to be missing hence the vertical can not operate.

Good luck and thank you for asking.
Customer: replied 5 years ago.

Thanks for the quick response Benimur. Please help me understand how easy it would be to fix the problem or whether this means simply trash the TV.

1. Please confirm - "vertical deflection circuitry" does not include the tube itself. I.e. Tube fialure unlikely to be the culprit with this type of problem.

2. In simple terms it sounds like you are suspecting a loose solder connection? Would this mean no likely component replacement required, but careful resuldoring of the connection could solve the problem?

Or would I need new components - flyback transformer or perhaps whole circuit board?

3. More infor to help shed more light:
Pressing any of the TV's buttons (for volume and channel change) - makes the blue line change colour, with hues of yellow and white appearing along it.

Pressing the AV in button makes the light momentarily disappear (leaving a completely blank screen like the TV is off). Pressing this button in quick succession makes the line disppear for a long time....
To your queries:
  • does not include the tube itself - very unlikely a faulty picture tube. If the tube is bad, there would not even be a line at all;
  • suspecting a loose solder connection - most likely if the thumping results to momentarily flicker or expands;
  • no likely component replacement required - yes for a cold solder issue;
  • careful resuldoring - very important. The distance from pin to pin of most ICs is only around 1mm;
  • new components - flyback transformer or perhaps whole circuit board - doubtful/very unlikely or if ever, inexpensive parts;
  • Pressing...buttons...blue line change colour - to be expected, normal;
  • Pressing the AV in button...light momentarily disappear - again to be expected, normal as the TV goes into momentary video mute.

The resoldering is very easy (if indeed it is a cold solder issue / thump test). It may be getting access to the solder side of the board that may be of a bit of a challenge.


Edited by Benimur on 1/4/2011 at 8:56 AM EST
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Customer: replied 5 years ago.
Thanks a lot, Benimur.