Sound has recently failed on the BBC channel on this receiver, leaving a humming noise. On
ITA the sound remains perfect with the picture on both channels remaining correct. Both tuner valves, VI and V2, are new and in working order and the sound i.f. (V9) and a.f. amplifier and output (V10) valves have been
checked by substitution.-R. K. Deakin (Stretford, Lancashire).
This fault is a frequent offender. We advise you to replace the 0.00uF capacitor decoupling
the screen grid of the sound i.f. stage on top of
the chassis. The present capacitor is a brown onP with rounded ends and must be changed for good quality Hunts W99 type.