In the snips below (from a "Sam's PhotoFact" manual),
View attachment 63679 View attachment 63683 View attachment 63684
we have a vibrator driven boost circuit, with L7 listed as a vibrator "hash" (arky-sparky "noise" common to DC vibrator choppers) suppressor.
After a simple clean-up and a vibrator points filing, on power-up the radio worked remarkably well (tuned to a local AM station), but with some minor static on the audio output that, over time (maybe 20 minutes) increased in volume until the audio was overwhelmed by it. During this time, C15 became "warm-ish".
My reading of the schematic is that C15 (a paper/wax 0.04 μF, 1000 volt (and maybe C16 and C17, as well, but neither have a parts descriptor like L7 & 8 [see above]) is also part of a "hash" suppression scheme. No inductance values are given for L7 & 8.
Voltages were nominal. Cutting C15's ground leg made no difference (i.e., the static got no worse or better and voltages remained nominal). I should note that the vibrator frequency is ≈115Hz.
Also not that C15's picture shows a thin black band indicating that it is polarized, although it is not an electrolytic (note C1A & B's symbol, vs C15's) as I understand the term.
(Finally the questions):
1. Am I right in assuming the function of C15?
2. If 1. is correct, what best modern cap to replace it with?
I know I'd be better off replacing the vibrator with a bistable 555 driven FET (or something like that) but I'm interested in keeping the current rig as "pure" as is practical.
Any other thoughts/suggestions are welcome.
View attachment 63679 View attachment 63683 View attachment 63684
we have a vibrator driven boost circuit, with L7 listed as a vibrator "hash" (arky-sparky "noise" common to DC vibrator choppers) suppressor.
After a simple clean-up and a vibrator points filing, on power-up the radio worked remarkably well (tuned to a local AM station), but with some minor static on the audio output that, over time (maybe 20 minutes) increased in volume until the audio was overwhelmed by it. During this time, C15 became "warm-ish".
My reading of the schematic is that C15 (a paper/wax 0.04 μF, 1000 volt (and maybe C16 and C17, as well, but neither have a parts descriptor like L7 & 8 [see above]) is also part of a "hash" suppression scheme. No inductance values are given for L7 & 8.
Voltages were nominal. Cutting C15's ground leg made no difference (i.e., the static got no worse or better and voltages remained nominal). I should note that the vibrator frequency is ≈115Hz.
Also not that C15's picture shows a thin black band indicating that it is polarized, although it is not an electrolytic (note C1A & B's symbol, vs C15's) as I understand the term.
(Finally the questions):
1. Am I right in assuming the function of C15?
2. If 1. is correct, what best modern cap to replace it with?
I know I'd be better off replacing the vibrator with a bistable 555 driven FET (or something like that) but I'm interested in keeping the current rig as "pure" as is practical.
Any other thoughts/suggestions are welcome.