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.).
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).
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.
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this generation of gm vehicles is easy to troubleshoot. the engine needs 3 things to run: compression, fuel, and spark. since you mention fire, i assume you have no spark.
disconnect any random spark plug wire and connect the end to a hei spark tester. crank engine and observe for spark. if you have no spark, disconnect the center terminal of the distributor cap and use the hei tester in the same manner. spark means cap and rotor bad or bad plug wireset. no spark means make more checks.
check for battery voltage and good ground on distributor. check for open or shorted ignition module or ignition coil windings. if power and ground is present and ignition coil tests ok, check for ignition pulses at coil primary. if you have no ignition pulses feeding the coil, change the distributor.
with that generation of vehicle, the ignition system will operate without help from the computer. don't even troubleshoot the guts of the distributor, if you change the cap, rotor, and anything else, it will be the same price as a remanufactured distributor, and might not fix the problem. if you troubleshoot a low volrage related issue (no pulses, shorted or open circuit, unstable timing, etc), change the whole thing.
The relay or relays that click disconnect the receiver from the speaker terminals so that no dc voltage can burn out the speakers. More than likely the power output transistor(s) are faulty. Look at the relay(s), determine the input and output connections. The inputs come from the output power transistor and emitter resistors area, the output of the relay(s) connect to the speaker terminals. Check for dc voltage on the input contacts in the range of 30-60 volts possibly. If dc voltage is found there then you have bad outputs, caps or emitter resistors. A word of caution -troubleshooting at this level requires advance knowlege of electronics, do not attempt this with out onsite help from a experience tech.
IF THE SPEAKER PULSES IN OR OUT WHEN YOU CONNECT THE LEADS TO AMPLIFIER, IT MAY BE OUTPUTTING DC WHICH WILL EVENTUALLY BURN THE VOICECOIL OUT. MOST TIMES AMPLIFIERS ARE DESIGNED WITH PROTECTION CIRCUITRY TO DETECT THIS CONDITION. A FEW RARE AMPLIFIERS WILL ACTUALLY PASS A DC SIGNAL FROM THE INPUTS, THROUGH THE AMPLIFIER, TO THE OUTPUTS AND ONWARD TO THE SPEAKERS, SO I SUGGEST THAT YOU REMOVE THE INPUT RCA'S AND RETEST. IF IT STILL DOES IT, THEN THE AMPLIFIER WILL NEED TO BE SERVICED.....V
I understand that you have tried connecting different audio source to the Receiver as some of the audio source will output only 2 channel audio.
I hope you have tried changing the Input mode and Input selector to get the surround sound.
Please disconnect the speakers with the receiver and clean the edges of receiver and speaker cables using solution like alcohol and try.
If the issue persists, please interchange the rear speakers with front speakers and vice versa and check if audio is coming to make sure that the speakers are working fine.
If the audio comes after replacing the speakers but not from surround speakers, the receiver requires service.
Follow the steps below to troubleshoot why there is no sound:
model-specific information is required to complete any of the steps in this
solution, refer to the operating instructions supplied with the product. Manuals
are available online in the Manuals/Specs/Warranty section of the Sony® eSupport Web site.
NOTE: Because each of these
steps represents a possible solution to this issue, check the sound after
completing each step.
Verify that the Audio/Video (A/V) receiver is set to the correct function or
Verify that the A/V receiver is not in the demonstration
Check all speaker connections to verify proper connection.
Depending on your model unit, select the main speaker output (A or B) that
corresponds to where the main speakers are connected.
IMPORTANT: If the main
speakers are connected to speakers A on the A/V receiver, the speaker output
must be set to A for sound to be reproduced.
Run a test tone operation to test the speakers if
your A/V receiver has this feature.
Verify the cables from the source component are connected properly to the
Connect the component to a different input on the A/V receiver.
Tune the A/V receiver to the new component input.
If the issue is still not resolved, replace the A/V cable between the
component and the A/V receiver.
NOTE: If all speakers operate
using the different input, then the first input on the A/V receiver is not
Connect a working speaker to the speaker output on the A/V receiver that is
If the issue is still unresolved, service may be required. The Sony® eService
Web site at http://eservice.sony.com/ can assist you in obtaining service
from a Sony Service Center or locating a Sony Authorized Servicer.
Are your speakers able to handle the 886's power. I have the same reciever and changed by speakers as the Denon would turn off instead of frying the speakers.
As for the digital, have you used the option to change your audio feed and video feed. (for example - I'll show photos through the front input but use the CD -digital for music. Maybe the audio feed is locked onto an analog input. Just a suggestion.
There is a matrix switching IC on the circuit board that switches and routes the sources. This IC (for the audio) may be damaged, or it is not being properly commanded by the uPC controler. You will have to send the reciever to a qualified service tech to have this verified. Troubleshooting this can get involved if the fault is more than just the matrix IC.
Your problem is somewhere between the tuner and video detector circuit.
The signal entering your TV carries: video,red color,and blue color as well as sychronizing pulses for color and horizontal and vertical deflection ( actually vertical sync. is derived from horizontal sync.) along with burst pulses to synchronize the color. After all these, the sound is an fm signal entwined with a pilot signal for stereo audio. WHAT a mess!
After the audio passes through all this, it is detected and sent to the audio processor.
If any frequency has drifted away from it's value then you loose the sound.
SO... your problem could be in any of the tuned circuits or in the audio processor IC (chip). Any component changing value could creat this problem. Most likely the audio processor IC. You'd need to have the set checked out by a tech to find your problem.