Hi Eric,
The grid voltage on the oscillator comes about by grid rectification. It is known as grid leak bias. The feedback is via the cathode to the grid and when the oscillator is running, grid current with the positive signal excursion forces grid makes the grid negative. When there is no oscillation, there is no negative voltage! This is the same bias on the subsequent stage and because there is no signal, there is no bias.
If the capacitor is the correct value and the grid resistances are okay, it will be either the 6K6 or the oscillator coil. Are you sure the coil connections are correct?
Terry
Quote:
Originally Posted by Eric H
Lets try a different approach here, I'm not understanding how this circuit works.
I'm trying to understand where the -18 volts that's supposed to be on pin 5 of the Horiz Osc comes from?
The horiz phase and horiz osc coils are two separate coils that are physically strapped together, they appear to be inductively coupled on the schematic (No iron between them so not coupled?) does the -18v depend on the horiz phase coil working or is it independent of that?
There is 200+ volts coming to C72, the 150mmf cap that goes to the phase coil, that's the only place I can see any voltage at all entering this circuit but maybe I'm missing something obvious?
The voltages to the 6AL5 are not horribly far off, somewhat low on pin 7 I think, 3.something where it should be 9.0, but I' going from memory here.
I know it's a hassle to have to download the schematic to see the whole circuit, sorry about that, perhaps I can scan it and post it in a single image later.
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