Sony KV-20FV12 Audio Buzz

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OrdinaryCyborg
Posts: 9
Joined: Mon Sep 13, 2021 4:40 am

Sony KV-20FV12 Audio Buzz

Post by OrdinaryCyborg »

Hey All! So I recently pick up a Sony KV-20FV12 and noticed it has constant static noise and a buzz in both the speakers and headphone jack. The speakers also pop when the volume is turned all the way down to off. Considering the technology, I wouldn't be surprised if the static is expected but the buzz definitely is not. So far I've recapped everything with long life nichicon's and nothing changed. I double checked all the traces leading into the audio card but couldn't find anything faulty or grounded. Honestly all the pcb's are in great shape with no visible corrosion. I've tried unplugging the speakers but the buzz is still there in the headphone jack. I even completely removed the tuner thinking that maybe it was creating interference but that didn't change anything. Adjusting the brightness on the flyback also did nothing. My next step is to maybe replace the voltage regulators. Any help or direction to look will be appreciated.
OrdinaryCyborg
Posts: 9
Joined: Mon Sep 13, 2021 4:40 am

Re: Sony KV-20FV12 Audio Buzz

Post by OrdinaryCyborg »

Quick update- After doing more research, alot of folks on audio forums say that bad transistors are the cause of most audio buzz in older electronics so I went ahead and ordered new old stock of all the through hole transistors on the main board. Probably overkill but I didn't want to leave any stones unturned. I tried to find newer replacements but I didn't want to potentially trade one problem for another plus I couldn't find all the proper datasheets.
Housematt
Posts: 18
Joined: Sat Oct 10, 2020 11:03 am

Re: Sony KV-20FV12 Audio Buzz

Post by Housematt »

I'm dealing with exactly this problem at the moment with some of my Supergun gear.

A lot of audio interferance can be caused by unintentional ground loops - Is there a way that you could be carrying Line Earth all the way from your source (console?), across your cables, and back through your TV to another Line Earth at a differnt impedance?

I guess what I'm asking is, what does the rest of your setup look like?
OrdinaryCyborg
Posts: 9
Joined: Mon Sep 13, 2021 4:40 am

Re: Sony KV-20FV12 Audio Buzz

Post by OrdinaryCyborg »

Housematt wrote:I'm dealing with exactly this problem at the moment with some of my Supergun gear.

A lot of audio interferance can be caused by unintentional ground loops - Is there a way that you could be carrying Line Earth all the way from your source (console?), across your cables, and back through your TV to another Line Earth at a differnt impedance?

I guess what I'm asking is, what does the rest of your setup look like?
The audio interference happens with nothing plugged into the tv. As soon as I turn it on it starts and i've tried multiple ac outlets. The buzzing/static is still present in the headphone/audio out jacks with the speakers removed. I have a ground loop noise isolator that I tried using on the headphone jack and it made zero difference. I'm currently convinced there's a failing component or components on the main board A causing the interference. I dont know the history of this tv but it was in slightly rough shape when I got it. The yoke needed a reset as most of the rubber spacers were falling off.
OrdinaryCyborg
Posts: 9
Joined: Mon Sep 13, 2021 4:40 am

Re: Sony KV-20FV12 Audio Buzz

Post by OrdinaryCyborg »

Ok this is my final update on this. No success on solving the my audio issues. I replaced several transistors and voltages regulators with little to no change. The best I can figured is the noise is there leading to the amp and the amp is well, amplifying it. I'm going to move to an external amp and wire the 5w tv speakers directly into it while using the stereo output from the tv. That output comes straight from the soundboard and while it does have buzz, modern more powerful amps do a great job at keeping it inaudible at low to medium volumes. I would bypass the tv circuitry completely BUT I want to use the tv remote for volume control still. I really can't diagnose it any farther without an oscilloscope and at this point, it's just not worth it.
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