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Convergence IC - Projection TV- STK4274

Discussion in 'Electronic Repair' started by Maxmel, Apr 15, 2006.

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  1. Maxmel

    Maxmel Guest

    Hi ,
    Can I replace STK4274 by a STK391-020 ?

  2. John-Del

    John-Del Guest

    Yes you can, it just won't work. Completely different animals.

  3. Maxmel

    Maxmel Guest

    Good to know. I did some search on Internet and that is the replacement they

    Tks for the info .

    Is there any replacement ?
  4. Why will it not work? According to the Sanyo datasheet the STK4274 is
    replaced by the STK391-020.

    As I have said before, you might want to include the previous post in your
    reply so that it is easier to determine what you are commenting about.

  5. Maxmel

    Maxmel Guest

    So , what is the verdic ??
  6. Sanyo is the OEM for these chips, and numerous techs have reported using the
    replacement successfully.

  7. Guest

    I have done it. I don't recall the exact pins, but you must jumper them
    together. IIRC they are the negative supply pins for the output stages.
    You also have to remove the two "bootstrap" caps.

    This is all easily identifiable if you look at the datsheets. The big
    problem is the case size. The 391 is wider. Thus you can only use it
    when the ICs are clamped to the heatsink, although one time in a Zenith
    (I was really in a pinch) I went ahead and changed it over to the newer
    heatsink from a junk board.

    It is still easier to just use the right part, but as we all know, ICs
    get discontinued. Then you have to buy them aftermarket and you can't
    really be sure you're getting good ones. At that point it'll be better
    to change over to the 391 rather than changing 4274s trying to find a
    good one.

    I just looked, you remove the caps between 5-6 & 11-12 and install a
    jumper between 4-13. Simpler than many factory mods, and quicker than
    changing an IC three or four times or troubleshooting a waveform
    generator that is working perfectly.

    Incidentally, in the past I would use standard OP AMP protocols to
    determine if the STK is bad. That means either a null point at the - in
    or the same waveform at the + and - in. This is not always conclusive I
    have found. I've had the indication that the channel was bad when it
    was in fact working perfectly. Apparently in some sets they let the
    output clip, but not bad enough to throw the convergernce off.

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