11-08-2017, 12:50 PM
http://www.nostalgiaair.org/Resources/232/M0013232.htm I plainly see part #84 on the schematic as a .002mf cap.
#84 is part of the negative feedback circuit for the audio amp. I would think if you changed it to a .05 at best it would alter the tonal quality of the sound and at worst it would oscillate uncontrollably.
As mentioned many times before here and on other forums testing old w/p caps is a waste of time. With modern test equipment they can give you an accurate assessment of the capacitance BUT they test at a very low voltage so it doesn't tell you anything about voltage leaking though the cap in question. 9vdc is virtually nothing by comparison to the hundreds of volt applied to it in it's the vacuum tube circuit it came out of. This is a critical factor as when there is leakage it can cause an upset in the bias voltages causing the tube it's associated with to to draw excessive current. Also can be the source hissing and popping sounds in the audio.
Off the soapbox.
#84 is part of the negative feedback circuit for the audio amp. I would think if you changed it to a .05 at best it would alter the tonal quality of the sound and at worst it would oscillate uncontrollably.
As mentioned many times before here and on other forums testing old w/p caps is a waste of time. With modern test equipment they can give you an accurate assessment of the capacitance BUT they test at a very low voltage so it doesn't tell you anything about voltage leaking though the cap in question. 9vdc is virtually nothing by comparison to the hundreds of volt applied to it in it's the vacuum tube circuit it came out of. This is a critical factor as when there is leakage it can cause an upset in the bias voltages causing the tube it's associated with to to draw excessive current. Also can be the source hissing and popping sounds in the audio.
Off the soapbox.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got it!
Terry
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
