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Sanyo CPP2930 TV, chassis A8-A29

Discussion in 'Hobby Electronics' started by Franc Zabkar, Mar 7, 2007.

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  1. Franc Zabkar

    Franc Zabkar Guest

    I'm working on an intermittent fault in a Sanyo CPP2930 TV, chassis
    A8-A29. The customer describes a vertical collapse (horizontal line)
    followed by a shutdown and restart. After this happens, the volume is
    at minimum.

    This article ...

    http://www.siliconchip.com.au/cms/A_30635/article.html

    .... talks about a service bulletin "dated 27-4-94 (no. 24) for the
    CPP2930 and 2530 models, the fault being: 'The TV set switches off and
    on (CPU resets momentarily) on VCR search mode'."

    The author states that "It was then just a matter of purchasing a kit
    of parts and fitting them on the SYNC and RESET PC board (VE2689)".

    I have the details of this rework (3 resistors, 1 capacitor) but am
    not certain that it will address the aforementioned problem. Is there
    anything else to check? A tap test has turned up no dry joints or bad
    connections.

    - Franc Zabkar
     
  2. Franc Zabkar

    Franc Zabkar Guest

    That's the first place I checked. I tried tapping and freezing but was
    unable to produce a collapse. I did observe an initial warm up problem
    where the height was reduced to about 2/3, and I traced the fault to a
    dry electro, but I'm not convinced that the total collapse is caused
    by the same component.
    Hopefully it is that simple, but I hate to fix something before I
    witness the fault.
    The SC article suggests that a particular VHS tape was able to
    consistently reproduce the fault. I suppose this could have been due
    to dropouts, but the author suggested that it may have been due to
    some Macrovision incompatibility.

    One thing which is confusing me is that the "Reset and Sync" board,
    which is the subject of the bulletin, appears to have two v/sync
    sources, a TDA2579B and an LA7210. I guess the first is for TV, the
    latter for VCR. I don't have a circuit diagram, BTW.

    - Franc Zabkar
     
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