05-22-2021, 09:25 PM
I think your in the ball park with those values.
Though tedious, make a temporary installation of the values found. Isolate the primary with a 10k resistor on the plate side then to a RF oscillator. Common connect the B+ and AVC connections to the IF, generator and the VTVM/scope. Use either the scope or a VTVM at high impedance and measure the RF as the generator is slowly swept through the IF pass band. If the values are correct then the slugs will not have to be moved.
Try other values if they get closer to the resonance if need be.
I have done similar to identify the resonance of unknown IF's from the junk box as well as pre-set IF's. They will be very close but not exact as the stray capacitance in the test procedure and in the radio is just a guess... Unfortunately, this test will not qualify a junque box IF as to having "SMD" or not. Must have B+ to do that...
I am in favor to not moving the slugs if at all possible, the IF passband shape may not be the same if the slugs are much closer or further apart to achieve resonance.
YMMV Chas
Though tedious, make a temporary installation of the values found. Isolate the primary with a 10k resistor on the plate side then to a RF oscillator. Common connect the B+ and AVC connections to the IF, generator and the VTVM/scope. Use either the scope or a VTVM at high impedance and measure the RF as the generator is slowly swept through the IF pass band. If the values are correct then the slugs will not have to be moved.
Try other values if they get closer to the resonance if need be.
I have done similar to identify the resonance of unknown IF's from the junk box as well as pre-set IF's. They will be very close but not exact as the stray capacitance in the test procedure and in the radio is just a guess... Unfortunately, this test will not qualify a junque box IF as to having "SMD" or not. Must have B+ to do that...
I am in favor to not moving the slugs if at all possible, the IF passband shape may not be the same if the slugs are much closer or further apart to achieve resonance.
YMMV Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”