This can be confirmed only by hearing if the outputs are working well. You can open the set and check to see if there is test tone( with a audio signal test) from the input of the power amplifier.
If so we can confirm that the power amplifier is working.
Now the noise in this case can be the potentiometer rubbing with dirt. If so use to vigourously to the left and right to clean out bu itself.
Now tthe possible fault can be failure of power to the preamp section, the failure of preamp or the failrue of the mode selector.
In all the above cases you will need to check with the audio injector to confirm the point of fault.
Try to trigger the selector mode many times, check if any other input is working than the connected one to confirm.
Now that your Main amp is working fine, a poor capacitor( short) can make the input cross over, but I think in this case it can be the preamp IC. or can be any of the logic circuits failure...
I was originally leaning in this direction as the volume appears to be microprocesor controlled. Not sure if this will be to advanced for me to attempt to fix. would you care to see the Scematics I downlowded?
New discovery. The board the the front and rear channel preamps are on are on a diferent board that the one for the Center and sub. The center has the same problem son there must be somthing comen here that is creating this problem before the audio hits the Preamps.
COULD BE RELATIVE TO THE MULTIFUNCTION IC. it can be the one with preamp,equaliser,and the audio seperator. Normally the boards are swapped to confirm as working will be difficult to probe unless we have an external jig & harness.
Good try you are coming to the point.
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What you are getting is excessive phase shift at the lower-frequency edge of the audio pass band, causing oscillation. This is almost always due to aging capacitors or preamp
.Replacing preamp or capacitors will surely solve the problem.
Hi,
check the coupling capacitors for the speaker outputs. It probably has quasi-complimentary transistor configuration in the amp section. If they loose capacitance the circuit can become unstable.
check the leads on the square transistors.If they are bolted down the leads sometimes break where they are bent.
post a comment for further assistance.
thank you for using fixya have a nice day:-)
Hi,
I like to fix things as pet projects...speakers are uncharted territory for me, but my cousin has that speaker and it rocks! You can't find it anywhere...
How's $25 and I'll pay for shipping ?
Thanks for considering (fingers crossed)
Danny
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Should I replace the capacitors on the Preamp? The power amp section seems to be fine as I can send audio to is directly via the pre inputs. Remeber I get this thumping sound on the pre out and headphones as well. Can bad capacitors on the main amp section create a problem for the preamp? Whe I rotate the digital volume control it make the thumping sound in the same positions every time.
There is no audio passing through the pre-amp also from the selected source.
I have a copy of the service manual in PDF if that helps but don't know how to post it or send it to you.
Should I replace the capacitors on the Preamp? The power amp section seems to be fine as I can send audio to is directly via the pre inputs. Remeber I get this thumping sound on the pre out and headphones as well. Can bad capacitors on the main amp section create a problem for the preamp? Whe I rotate the digital volume control it make the thumping sound in the same positions every time. There is no audio passing from the selected source through the Pre-amp
Should I replace the capacitors on the Preamp? The power amp section seems to be fine as I can send audio to is directly via the pre inputs. Remeber I get this thumping sound on the pre out and headphones as well. Can bad capacitors on the main amp section create a problem for the preamp? Whe I rotate the digital volume control it make the thumping sound in the same positions every time. There is no audio passing from the selected source through the Pre-amp
After removing about 60 screws on the back panel I was able to get the pc board with the pre-amp. There are about 70 small electrolitic capacitors on this board. Should I start with the capacitors on the output side of the transistors? I have downloaded the service manual with the scematic of this board to help guid me as to what is what. Also, I would think if there was a bad capacitor it would only affect one channel as the cicuits seem to be somewhat descret. Thoughts?
I don't think ti is the potentiomenter as when it is rotated the digital display cleanly increses the display in DB.
I know the power amp is fine as I can send audio into the pre in and everything sounds great.
I tried many inputs and get the same result.
I can go with a power problem though to the Pre-amp as that seems to be somthing comen to all channels as they are all having the same problem. Any more thoughts?
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