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  1. #1

    Re:-Toshiba 2857DB television circuit.

    I would really appreciate if anyone could supply me with a copy of the service info for the 2857DB, or even just a circuit diagram (PDF format ideal) as I have a peculiar intermittent suspected frame timebase fault in this set, and because its a set that has been serving me well for the past nine years I am loathe to update it as its superior audio quality would be greatly missed, that is as well as it being amongst the best of sets for its CRT picture quality.

    The fault by the way being an intermittently appearing white line superimposed on the picture and which runs up from the bottom of the screen to about 1/4 way up, then it starts jumping up and down slightly and occassionally drops under the masking, and when it does the picture is seen to cramp in that area.

    The intensity of the line is also picture content dependant, as its not noticed on dark backgrounds but gets a lot brighter when over a light background.
    Last edited by jb38.pch; 13th Apr 2009 at 15:32. Reason: (additional info)

  2. #2
    On futher investigation into the problem, this being aided with a copy of the circuit diagram kindly supplied to me via the "private message" facilty on this site suggested that the problem was most likely caused by a dry joint developing on either the frame output IC's pins or alternatively on the power regulator transistor that feeds it.

    All pins concerned were resoldered, and (touch wood!) after three days of use so far there has been no signs of the fault reappearing.
    Last edited by jb38.pch; 20th Apr 2009 at 16:41.

  3. #3
    Quote
    Quote: jb38.pch
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    On futher investigation into the problem, this being aided with a copy of the circuit diagram kindly supplied to me via the "private message" facilty on this site suggested that the problem was most likely caused by a dry joint developing on either the frame output IC's pins or alternatively on the power regulator transistor that feeds it.

    All pins concerned were resoldered, and (touch wood!) after three days of use so far there has been no signs of the fault reappearing.
    Final update one month later - TV is used for about 9 hours each day and is still perfect after having resoldered the aforementioned joints, this liable to indicate that it was indeed a dry joint that was the cause of the problem albeit that this has taken about 10 years to show up!

  4. #4
    Good news!!!

    The simple fact that most CRT TV's generate a fair amount of heat adds to the dry joint theory!! I had a friend who ran a TV repair shop and he said that 99% of internmittent TV faults were dry joint related!!

    Glad it running well

    Chris

  5. #5
    Quote
    Quote: ChrisHarding
    View Post
    Good news!!!

    The simple fact that most CRT TV's generate a fair amount of heat adds to the dry joint theory!! I had a friend who ran a TV repair shop and he said that 99% of internmittent TV faults were dry joint related!!

    Glad it running well

    Chris
    Yes, very much so! and just to confirm that this indeed was the problem as the set, which as aforementioned runs about 9 hours or so every day, is still absolutely perfect. (If I dare tempt Murphy's law!)

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