06-01-2015, 07:44 AM
Whilst playing with 7C I notice that the audio was a little distorted. So measured some voltages and came to the conclusion that the coupling condenser to the 42 tube was leaky. Located it but noticed that there was a
100K 1W resistor that was disconnected from it's terminal strip. Reconnected it but it made no difference and there was no voltage across it. Hmmm.... Broke out the schematic and found that it supplies the screen grid voltage to the 6B7 (1st audio/det/avc). But why isn't there any voltage there? Because someone cut out a jumper from a near by terminal strip to that resistor's connection. Checked the resistor and was good. Replaced jumper and condenser. Dang thing plays twice as loud and sound much better. Condenser was OK but got replaced anyway.
Terry N3GTE
100K 1W resistor that was disconnected from it's terminal strip. Reconnected it but it made no difference and there was no voltage across it. Hmmm.... Broke out the schematic and found that it supplies the screen grid voltage to the 6B7 (1st audio/det/avc). But why isn't there any voltage there? Because someone cut out a jumper from a near by terminal strip to that resistor's connection. Checked the resistor and was good. Replaced jumper and condenser. Dang thing plays twice as loud and sound much better. Condenser was OK but got replaced anyway.
Terry N3GTE
