Hello Dual Lovers!
Patient: CV1400.
Symptoms: hiss in the left channel (speaker) when the amp stays at idle (no signal). The hiss increases with the volume knob position. Both channels functional, filters functional, high frequencies in the left channel at a bit lower volume and less natural in comparison to the right one.
After quick investigation and playing with connection plugs between final stage and preamp boards, it seems that the issue must be located on one of the preamp boards.
Final stage input disconnected from the preamp board = no hiss.
Final stage input with flipped channels = hiss in the right channel (speaker).
Preamp board input disconnected = hiss in the left channel remains -> the preamp boards seem to be the source of the hiss.
When I touch C1162 housing with a rubber glove, the hiss in the left speaker increases in volume and a lower frequency buzz appears. When touching C1162' only a very low-volume hiss appears in the right speaker - it can barely be heard. C1162 and C1162' measured on the board have very similar parameters in terms of resistance - no short circuit there, metal housings vs chassis show several mega ohms. Measuring the capacity requires unsoldering the caps. C1166 and C1166' are keeping their original parameters.
As always I count on your experience as I prefer to investigate rather than "let's replace the caps and see what happens" method. The weapons I have are: a multimeter, a capacitor tester, a Chinese touch-screen oscilloscope and pc-based generator/analyzer + CV1400 service manual. I will try to follow the L and R signal on the preamp boards and search for the point where the hiss is being introduced (amp at idle) but maybe the behavior of the unit reminds you of some common issue.
This particular CV1400 belongs to the series with plastic side panels and "golden" capacitors on the final stage board. Looking untouched by any service.
All the best,
Mike.