04-05-2022, 01:45 PM
The 12 uF cap connected to the rectifier tube cathode is somewhat critical in that it should not be drastically increased over what was originally specified. The capacitance in this location affects the peak current drawn by the rectifier tube each AC cycle and a much larger value can exceed the tube's peak current rating. A larger value also will tend to increase the DC voltage output of the power supply. With today's higher AC line voltages, you really dont want the DC output increased even more.
As far as the 16 uF cap after the field coil, its value is not critical and a larger value here within reason will reduce hum without any negative effects. The 40 uF in that location would be ok.
If I was replacing the caps, I would probably go for 15 or 16 uF for the 12 uF and 20 or 22 uF for the original 16 uF. Keep in mind the original caps had very loose tolerances on their capacitance, typically -10% to +80%, so the original 12 uF could have ranged from 11 uF to almost 20 uF as installed by the factory.
As far as the 16 uF cap after the field coil, its value is not critical and a larger value here within reason will reduce hum without any negative effects. The 40 uF in that location would be ok.
If I was replacing the caps, I would probably go for 15 or 16 uF for the 12 uF and 20 or 22 uF for the original 16 uF. Keep in mind the original caps had very loose tolerances on their capacitance, typically -10% to +80%, so the original 12 uF could have ranged from 11 uF to almost 20 uF as installed by the factory.
