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audio amp

Discussion in 'Electronic Repair' started by [email protected], Jan 28, 2006.

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  1. Guest

    I have an Adcom GFA 7605 and one of the channels blew. Now there's
    about 60 volts on that channel's speaker terminals.
    I took the board out. It looks like transistors Q8 and Q16 need
    replacing. I don't know how to identify them. Q16 is in a TO-92 has
    what looks like house numbers on it.
    KSP
    42
    -209
    I would have to remove Q8 to see its face. It has four pins.
    I did a little troubleshooting with a voltmeter by probing different
    spots on the bad board and comparing to the readings I took at the same
    points on a working channel's board. The region of the board with the
    inappropriate high voltage readings contains those two transistors.
    Q16 is not cracked but looks a bit singed and I can't tell about Q8 but
    one of its pins has the wrong voltage. Of course a bunch of other
    solder points on the board have wrong voltages too, but one or both of
    those transistors look to me most like the culprits.
    I could try contacting Adcom but it seems unlikely they would help me.
    How should I fix this amp?
     
  2. I have found Adcom to be very helpful when I have contacted them.

    Leonard
     
  3. DaveM

    DaveM Guest

    There is a listing in the NTE XRef that crosses the KSP42 to a NTE287,
    which is a 300V NPN in a TO-92 case. The -209 might be a beta grouping for
    that part, or some other special selection criteria.
    --
    Dave M
    MasonDG44 at comcast dot net (Just substitute the appropriate characters in
    the address)

    Never take a laxative and a sleeping pill at the same time!!
     
  4. Guest

    Helpful, thanks.
     
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