11-04-2017, 01:04 AM
I've been going over the circuit of my ECC85. Simplified, there's a triode RF amplifier and a triode oscillator. The IF is 10.7 megahertz. Of interest to me was the oscillator variometer. The primary L5 is one end at chassis potential. L6 leads to chassis via 33 K with the other end at the grid of the oscillator triode. This is if I follow it correctly. The Saalburg shows a full photo schematic of this FM double triode circuit. As we know so far I only have FM and the FM tuning is now ganged with the moving vane capacitor. Originally it was not and had been disabled by someone. Of course, now I know exactly what's happening as the dial chord controls the FM slugs yet the moving vane tuner is dead. As of yet I am not sure how to test the ECC85 anode voltages as these are not on the PCB boards. Of course I know they are OK. I am not far off being able to work out much of this set by circuit familiarity but 2 tuner systems was new to me. I'm glad I waited because when I messed with it months ago, I had insufficient knowledge. And I recall R355 gave me such a kick via C60's charge, I shot across my boat like a scalded cat. Bloody dangerous hobby when you're self taught. Why did I get that shock? Well HT feed to R35 was disconnected so C60 retained it's full 230 odd volts. That dropped when I touched it and acted as a "voltage divider".
