Question about Sony FD Trinitron WEGA KV-32FS120 32" TV

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Audio Pulses Off & On at Random (all speakers) (all inputs)

After much troubleshooting & talking with Sony tech support;
I changed the''M'' board (contains audio system signal processing, system control micro,etc.).
--Same Problem--
Even though all audio outputs of this ''M'' board pulse off & on, as seen on the oscilloscope,(even with the signal paths to the final audio output amps disconnected -- ahead of the muting buffer circuits), I changed the two audio output ICs (in accordance with a suggestion from one of the Sony support engineers).
-Same Problem-
All applicable supply levels seem OK (audio processing and outputs).
Blocking applicable mute lines, without disconnecting the signal lines to the amplifiers, does not solve the problem.
Immediate muting ''buffer'' stages at the audio output ICs are not falsely activating.
Disconnecting audio signals to the audio final amps and properly blocking muting signal activity eliminated the associated popping / pulsing sounds that accompany the associated audio off on problem; however, I would have to go back to the owner's home & recheck to see if I could still hear a ''whisper'' of the faint sound of this pulsing activity.
Problem occurrs when using any audio input, including the tuner.
Thinking that there might be some erroneous interrupting digital system control message on the serial data buss line,I tried disconnecting serial clock & data lines from the tuners and, additionally, also disconnecting the rear A/V connection board (this caused audio drop out except for the pulsing / popp sound, which likely results from the triggering of the muting buffers by the audio processing operation malfunction). Other sections, such as the line doubler digital video processor, could not be disconnected with any practicality.

-Same problem-

Thanks for ''hearing''/ considering my case.

Sincerely,
Franklin Thomas
thomastv@bellsouth.net







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  • Sony Master
  • 4,806 Answers

There could be interference with another device, remove all of you other devices especially with an amp or speakers, disconnect these and try the process again

regards

Posted on Dec 09, 2008

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