PYE P65PMBQ:Hum on mains
This receiver can be operated from batteries or A.C. mains, but on mains a prominent hum was evident. After checking all the sources in which one would expect to find hum introduced, it was eventually found to be picked up by the grid resistor to the output valve ( a separate output valve is used for mains operation, mounted on the mains power unit).
The resistor in question is R22 (Trader sheet 1114) and it was anchored to an unused pin (pin 3) on the rectifying valve holder V6. When it was lifted off the hum stopped. It was transferred to an adjacent unused tag and worked normally