Quote:
Originally Posted by Notimetolooz
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You then might be able to peak the sound IF and adjust the discriminator for zero volts output. Using a scope would be the best way to see the results.
You would first need to make sure the tuner was adjusted correctly.
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Unfortunately that will not work here because we are dealing with a split sound set and not intercarrier! Because the set top box goes through the tuner, the fine tuning (local oscillator) in the tuner will change discriminator zero. In fact, when the set is properly aligned, each time you change channels, you are always adjusting the fine tuning for discriminator zero!
You must use only a crystal calibrated 21.25MHz oscillator applied to the IF input to initially set discriminator zero. You cannot do it with anything applied to the antenna terminals.
I would not worry about discriminator zero at this point because the ball is out of the ballpark. Let us find the audio first and then find a way to set discriminator zero.
I have a deep hunch the 5.1 ohm filament resistor is bad.