10-06-2017, 10:19 AM
Hi Bob,
>With the shield in place and I touch the grid cap of the 36 detector/oscillator the reception also improves.
Forget to ask is this with an antenna connected?? Does the reception get much better when you touch the cap of the rf vamp tube??
> I used the chassis and electrolytic capacitor negative as ground points in separate tests.
Should use chassis gnd for voltage measurements. When you use the - side of the filter in adds any negative bias voltage to the total reading so it can be confusing. Also your modern meter has a very high input impedance so it doesn't load the circuit like the 1930's meter that has 1 or 2K input.
On your AA5 sets the chassis is floating, the - side of the power supply isn't tied directly to the chassis so in this case you would use the - side of the filter to test voltages.
> What should happen when the tube shield is removed?
Best case is that it won't have any effect worst case it will squeal like mad and tuning the tuning cap may cause some changes better/worst.
My other thought is at perhaps #5 and #15 are out of alignment. These would be the other two trimmers on the tuning capacitor, the third one tunes the osc section. Set your dial at 1480kc and an antenna connected you should hear WDAS. If not adjust the osc trimmer till 'DAS is at 1480. Next adjust 5 and 15 for best reception (loudest). See if that helps.
>With the shield in place and I touch the grid cap of the 36 detector/oscillator the reception also improves.
Forget to ask is this with an antenna connected?? Does the reception get much better when you touch the cap of the rf vamp tube??
> I used the chassis and electrolytic capacitor negative as ground points in separate tests.
Should use chassis gnd for voltage measurements. When you use the - side of the filter in adds any negative bias voltage to the total reading so it can be confusing. Also your modern meter has a very high input impedance so it doesn't load the circuit like the 1930's meter that has 1 or 2K input.
On your AA5 sets the chassis is floating, the - side of the power supply isn't tied directly to the chassis so in this case you would use the - side of the filter to test voltages.
> What should happen when the tube shield is removed?
Best case is that it won't have any effect worst case it will squeal like mad and tuning the tuning cap may cause some changes better/worst.
My other thought is at perhaps #5 and #15 are out of alignment. These would be the other two trimmers on the tuning capacitor, the third one tunes the osc section. Set your dial at 1480kc and an antenna connected you should hear WDAS. If not adjust the osc trimmer till 'DAS is at 1480. Next adjust 5 and 15 for best reception (loudest). See if that helps.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got it!
Terry
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