Pye Fenman II puzzle

[Boulevardier]

I have a Pye Fenman II that is exhibiting a strange problem. When the volume control is zeroed (fully a/c), there is still a trace of the audio signal audible through the loudspeaker. I’m not enormously worried, but the wife has the ears of an elkhound, and says it’s distracting when just turned to minimum volumr without turning off.
I can’t find any way of getting rid of this trace of audio. Grounding the volume control wiper doesn’t remove it, nor does grounding the control grid of the following audio valve.
Anyone have any tips as to where to start looking for the problem. I have another Fenman II that doesn’t have this problem, so it’s not a characteristic of the design, and I don’t remember having had the problem before with any other set. Presumably it’s signal breakthrough into a later stage of the audio amp.

Mike

[cathoderay57]

Hi Mike,
I've come across this once before with a set using a 6Q7 detector/pre-amp. The problem turned out to be a cathode bypass capacitor had lost most of its capacity. In your case check/replace C41 (EBC41 cathode) and C78 (EABC80 cathode). Component numbering is per Pye datasheet. Cheers, Jerry

[Boulevardier]

Originally Posted by cathoderay57

Hi Mike,
I've come across this once before with a set using a 6Q7 detector/pre-amp. The problem turned out to be a cathode bypass capacitor had lost most of its capacity. In your case check/replace C41 (EBC41 cathode) and C78 (EABC80 cathode). Component numbering is per Pye datasheet. Cheers, Jerry

Hi again Jerry
You are undoubtedly a genius! It was indeed C78, the EABC80 cathode bypass capacitor.
What an obscure fault, and you were spot on in remembering the one time you'd come across it!
Working beautifully now.
Thanks again, and hope to see you again soon.

Mike