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Sony STR-DE915 no coax digital audio.

Discussion in 'Electronic Repair' started by David Farber, Jun 21, 2007.

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  1. David Farber

    David Farber Guest

    I repaired this Sony STR-DE915 receiver which had no output on any of the
    channels even though the dc output was normal and the speaker relays were
    clicking on. The culprits were two AC muting transistors, Q503 and Q512,
    which are activated from the CPU.

    I tested the analogue portion of the receiver and that was ok. Then I hooked
    up a Marantz DV6200 DVD player to it and it worked fine with an optical
    cable hooked up to it but when switching the input to a standard coax cable
    as well as switching the input mode to "Digital (AC-3 RF)" there was no
    sound. The digital coax jack on the back is labeled, "LD/DVD IN, AC-3 RF."
    Is this not compatible with the current Dolby digital technology of the
    Marantz DVD player?

    Thanks for your reply.
  2. Deke

    Deke Guest

    I have that same amp. Its blown up twice, and is one of the reason I
    dislike Sony.
    Make sure you select the correct source on the front of the unit. And
    while it may say AC-3 RF, the Sony will not decode a RF must be
    demodulated first.
    I found that out the hard way, when I first bought my amp to hook up to my
    laserdisc AC-3.
    While your at it, add a heat sink to the chip for the rear channels. It
    runs very, very hot, and has no heat sink.
  3. HTH
    Your probably thinking of one or more driver IC's. (STK 350-230 or
    uPC2581)The rear amps use heatsink mounted output transistors, same as all
    the other channels. They do run the pants off those...

    Mark Z.
  4. David Farber

    David Farber Guest

    Yes, the correct source is selected on the receiver and the input is coming
    from a DVD player, not an LD player. I thought it would need no other help
    for the signal to be decoded so I'm still wondering if the receiver is bad
    on the coax input or something else is going on.

    Thanks for your reply.
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