04-25-2017, 02:24 PM
Mondial:
In response to your comment I pulled the IF apart to add a 390 pf capacitor in series with the IF trimmer. Before I did this, out of curiosity, I checked the capacitance of the trimmer with my Heathkit capacitance checker. I checked it with both coil leads disconnected. With the trimmer screw tightened completely the capacitance of the trimmer is about 60pf. This number seems too low rather than too high. As I loosened the trimmer screw the capacitance dropped.
To confirm this I checked a trimmer out of a Grunow 580 that was in my junk pile because of open coils. Capacitance of this trimmer was 150 pf with the screw tightened and as the screw was loosened the capacitnce dropped.
Based on this comparison it seems like I should be increasing capacitance by adding a capacitor parallel wih the trimmer.
Am I thinking correctly?
Does anyone have an idea what the capacitance range of this Philco trimmer should be?
Thanks, Bob
In response to your comment I pulled the IF apart to add a 390 pf capacitor in series with the IF trimmer. Before I did this, out of curiosity, I checked the capacitance of the trimmer with my Heathkit capacitance checker. I checked it with both coil leads disconnected. With the trimmer screw tightened completely the capacitance of the trimmer is about 60pf. This number seems too low rather than too high. As I loosened the trimmer screw the capacitance dropped.
To confirm this I checked a trimmer out of a Grunow 580 that was in my junk pile because of open coils. Capacitance of this trimmer was 150 pf with the screw tightened and as the screw was loosened the capacitnce dropped.
Based on this comparison it seems like I should be increasing capacitance by adding a capacitor parallel wih the trimmer.
Am I thinking correctly?
Does anyone have an idea what the capacitance range of this Philco trimmer should be?
Thanks, Bob
