19-12-2016, 08:05 PM
Hi.
The only way the valve would cause zero volts on the anode is a short from Anode to cathode and that is assuming the triode cathode is returned to chassis (ground) very very unlikely. If its an AC set (with mains transformer) then pulling the valve would give you supply on the anode connection in the unlikely scenario the valve was duff.
In normal practice (virtually all AM FM superhet valve sets) the anode will be connected to the Osc TX primary, the HT side of it will feed via a resistor around 10-39K ohm and back to the AM FM switching that will have HT contacts to cut the oscillator HT feed on FM.
There are some variations on the theme on some sets but they do follow similar circuitry.
My bet is the switch contacts dirty, broken or inadequate mechanical movement due to wear, dry soldered joints if the switch bank is soldered to a PCB or a simple O/C in the wiring unless the coil is still duff.
The only way the valve would cause zero volts on the anode is a short from Anode to cathode and that is assuming the triode cathode is returned to chassis (ground) very very unlikely. If its an AC set (with mains transformer) then pulling the valve would give you supply on the anode connection in the unlikely scenario the valve was duff.
In normal practice (virtually all AM FM superhet valve sets) the anode will be connected to the Osc TX primary, the HT side of it will feed via a resistor around 10-39K ohm and back to the AM FM switching that will have HT contacts to cut the oscillator HT feed on FM.
There are some variations on the theme on some sets but they do follow similar circuitry.
My bet is the switch contacts dirty, broken or inadequate mechanical movement due to wear, dry soldered joints if the switch bank is soldered to a PCB or a simple O/C in the wiring unless the coil is still duff.
