I recently picked up a 1980s Sansui amp, tuner, turntable and cassette deck for pennies . I know these were made after the great days of Sansui but the turntable is fine - direct drive and sounds good. The tuner works too. the cassette deck has liquified belts and I thought initially that the amp was OK. However, on closer listening it has noisy output on both channels. The noise increases with volume and responds to tone controls and balance - so I thought power caps and changed them but no change at all.
I put my scope on the speaker outputs and got a crazy, spiky output. I noticed that touching the metal part of the case (the sides and fascia are plastic!) caused the noise to reduce and change but not disappear. Now these amps (Sansui A501) do not have any ground connection on the input plug - just 2 pins for live and neutral. So i connected a ground lead to the grounding terminal on the back and then tried the scope again . Now I get a lovely 50Hz curve of a few millivolts at normal listening levels - at a higher level when phono input is selected.
So now what should be my next step? It seems to me like the power supply is not smooth so could it be one or more of the other electrolytics
I put my scope on the speaker outputs and got a crazy, spiky output. I noticed that touching the metal part of the case (the sides and fascia are plastic!) caused the noise to reduce and change but not disappear. Now these amps (Sansui A501) do not have any ground connection on the input plug - just 2 pins for live and neutral. So i connected a ground lead to the grounding terminal on the back and then tried the scope again . Now I get a lovely 50Hz curve of a few millivolts at normal listening levels - at a higher level when phono input is selected.
So now what should be my next step? It seems to me like the power supply is not smooth so could it be one or more of the other electrolytics