Jack Schmidling wrote:

I need some help and can not find the answer anywhere.

When neutralizing a triode, how much leakage between grid circuit and
tank circuit is allowed?

I am looking at the output of the final loading cap with a scope and get
a few volts of RF when the NC is nulled. This is with 20 ma grid drive
or about 10W input. The output just tickles the wattmeter on the 30
watt range and rises to about 10w when the NC in moved from the null
position.

Second question: should I see any leakage when the filament is off?

Thanks for your help.

Jack




What type of circuit: grounded grid or ground cathode?

Grounded grid with input circuit below chassis should require no neutralization.
The chassis provides isolation.

Leakage with filament 'OFF' is common in a grounded cathode circuit' The
inter-electrode tube capacitances are still there. So, circuit stray capacitance
and tube capacitances still need compensation.

Leakage with the tube removed indicates inductive coupling between the input
circuit [grid] and the plate tank circuit. Either a lack of input stage to
output shielding or the two tank circuit coils are not at 90 degrees relative to
each other [90 degree orientation yields minimum mutual inductance].