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Discussion in 'Troubleshooting and Repair' started by scientifico, Aug 15, 2012.

  1. scientifico

    scientifico

    62
    0
    Mar 13, 2012
    Hello, the screen of my old Toshiba TV starting with a line at the bottom became even smaller until all the image is concentrated at the center, do you know what could it be?
    When I give it a blow it fixes for a while but then it's the same...
    I attach 2 images, thank you :)

    [​IMG]

    [​IMG]
     
    Last edited: Aug 22, 2012
  2. Comnics

    Comnics

    20
    0
    Feb 12, 2012
    the problem of your TV is the vertical section, try to replace the electrolytic capacitor on that section.
     
  3. davenn

    davenn Moderator

    13,246
    1,745
    Sep 5, 2009
    yup agreed.... it will either be one or several electrolytics in the vertical output section or it may be, depending on the age of the TV, the vertical output transistors or in a more modern set ( ~ 1990's onwards) its usually an IC

    you may find a bulging or leaking electro capacitor ot it may look normal but just dried out

    cheers
    Dave
     
  4. debe

    debe

    229
    62
    Oct 15, 2011
    If it works by hiting it then it will be dry solder joints probably on the Vert ouput IC.
     
  5. davenn

    davenn Moderator

    13,246
    1,745
    Sep 5, 2009
    show a pic of the whole inside maybe a couple of different angles
    not enouogh seen in that pic to go by

    Have you googled for a service manual or at least a schematic ?
    it would give you part numbers for the various transistors IC's etc so at least you would know you were looning for eg. IC5

    Dave
     
  6. whiskeycat

    whiskeycat

    8
    0
    Apr 11, 2012
    vertical output IC

    Look for a IC that is mounted on a heatsink...it might marked TDA #### for example and have 9 or more pins...use datasheetarchive.com to look up part no. it will be listed as a vertical output IC.

    Many times I've fixed this problem just by resoldering the connections on the pins of the IC..it would be a good idea to look closely at all of the solder joints in your set.

    If that doesn't fix the problem try replacing the capacitors next to it...there's usually 3-4 caps there or maybe the IC itself is shorted.
     
  7. scientifico

    scientifico

    62
    0
    Mar 13, 2012
    I looked the schematic and I found LA7837, is this the vertical IC of my tv?
     
  8. davenn

    davenn Moderator

    13,246
    1,745
    Sep 5, 2009
    OK, thats good, now the datasheet for that chip shows a number of electrolytic capacitors used around it..
    Find that IC on the circuit board and take a sharp well lit pic of that area showing the chip and components immediately around it. say from a couple of angles :)

    post them and let us look at them


    Dave
     
  9. scientifico

    scientifico

    62
    0
    Mar 13, 2012
    some pic of that area...

    [​IMG]

    [​IMG]

    [​IMG]
     

    Attached Files:

    Last edited by a moderator: Aug 22, 2012
  10. scientifico

    scientifico

    62
    0
    Mar 13, 2012
    I found that one of the electrolytics capacitors around the IC tends to decrease its resistance instead of increase as others do when tested with a tester, can this be the problem?
     
  11. davenn

    davenn Moderator

    13,246
    1,745
    Sep 5, 2009
    I would seriously consider the 3 smallest (physical sized) caps tat are close in to the IC, the smaller ones dry out faster :)
    Then go through the larger ones if need be

    There is always still the possibility that the IC itself has failed... the cap replacement is an easier first option

    cheers
    Dave

    PS..... I resized your images both in physical size and kb size it makes it much easier to download. Try to keep images to 800 x 600 or smaller and kb size to preferably less than 100kb :)
    They are now also uploaded to and stored on the forum server ...which is always a better way, cuz if your other site fails then the pics are lost
     
    Last edited: Aug 22, 2012
  12. scientifico

    scientifico

    62
    0
    Mar 13, 2012
    sorry i tought the bigger the image the more details :)If the IC has failed, would it fix for a while by hitting the tv as happen?
     
    Last edited: Aug 23, 2012
  13. davenn

    davenn Moderator

    13,246
    1,745
    Sep 5, 2009
    naaa they were just too big and take too long to d/l lol :)

    ok I seemed to missed the original comment about giving the unit a "blow" I probably at that time didnt realise you were referring to hitting it. :rolleyes:

    OK then that really leads to the probability of dry joints, which I now see debe referred to a way back.
    You need to resolder everything in that area ... all the caps, resistors, pins on that IC, any fly leads from that area

    see if by selectively tapping different areas harder or lighter you can narrow down the most sensitive area of the board. Just to confirm that the fault is in that area of the board and not in the wires from to the vert deflection coils or the connections at the coils .... those coils are on the neck of the tube.

    Dave
     
  14. scientifico

    scientifico

    62
    0
    Mar 13, 2012
    well I resoldered some components and now the video seems working but there is no sound neither from the earphone plug ...
    I checked all the switches and connections but nothing, I hope I haven't damaged the board :(
     
    Last edited: Aug 23, 2012
  15. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,174
    2,690
    Jan 21, 2010
    So, have you seemingly fixed the video problem?

    And created a new one?

    My first suggestion would be to look for any connector that you may have removed and not replaces, or knocked while getting the board out.
     
  16. scientifico

    scientifico

    62
    0
    Mar 13, 2012
    lol I just forgot to connect the audio voltage supply wire :eek: on the old joints there was a red non conductive thing coming out from them, you know what is that? Thanks all for the support :)
     
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