Buzzing on a Sony 5-303W

[Jonathan]

Well, I recapped the whole set except for a 1uF 100V and a 2uF 50V electrolytics on the sweep board. I also changed the stinky selenium rectifier with a modern one. The set looks beautiful, the picture is stable and sharp, the sound is clear, except for the buzzing.

How does one fix the buzzing? The buzz seems to change with the picture. I remember reading on the photofact (1st page) to adjust the discriminator secondary. Could it be the two audio discriminator diodes? The 5-303W troubleshooting guide (purchased from servicemanuals.net) says iut's either the two diodes or a capacitor has lost capacitance.

Also, I never replaced the 5uF capacitors in the IF board because I never had 4.7uF caps that had the right voltage rating. I doubt they have anything to do with it, but I'm not sure.

Thanks.

Jonathan

[peverett]

Does the set have a ratio detector for the FM audio detection or true limiter -discriminator setup?

If it is a ratio detector, there is an electrolytic capacitor in the ratio detector circuit that, if bad, can increase noise and buzz.

Due to cost, very few TV manufacturers used true limiter-discriminator setups.

Buzz is caused by the AM modulation of the picture interferring in the FM audio detection circuit. If it is not a bad component, the sound section probably needs re-alignment.