Quote:
Originally Posted by Leon Crampin
The 170A chassis utilises the EF39 IF amplifier as an audio preamplifier stage on "gram". The anode supply is disconnected and the screen grid of the EF39 is used, effectively as a triode anode. The screen grid decoupling capacitor is then used to couple the audio to the EBL31 control grid.
Leon.
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Yes not just the EBL1 output valve in the 650A. The same arrangement is used though using an EF9 Ct8 side lock base. The pickup is shunted by a 0.5 megOhm resistor and fed via the secondary coil of the first IF stage to the grid of the EF9. A switch in the HT feed via the first IF primary cuts the anode supply to the oscillator EK2 muting the radio (so worth checking this switch if the radio isn't working!).