Hello to all,
I have read in a couple of service books that if you suspect a bad paper cap that you can parallel another one over it. I know that if you parallel caps they increase in value.
Is this common practice? If so and you have a cap say .01, .047 .005 Mfd which size cap value would you parallel on them? If this is not common practice or dangerous let me know and I won't even attempt.
Thanks
Mitch

Hi Mitch,

Paralleling caps is usually only done to get an odd value, one not commonly available.
I have placed a capacitor in parallel if I suspect a capacitor is open.
Wit paper caps, though, I don't waste time troubleshooting on them, I just replace them. Many are leaky and placing a capacitor in Parallel with a leaky one won't do any good.
By the way, you are right about paralleling capacitors. Their capacitance values add in parallel, but not their voltage ratings, so if you parallel a 0.01uf and 0.005uF capacitor you get 0.015uF at the voltage rating of the lower voltage rated capacitor.

Best Regards,

Bill Grimm

:Hi Mitch,
:
: Paralleling caps is usually only done to get an odd value, one not commonly available.
: I have placed a capacitor in parallel if I suspect a capacitor is open.
: Wit paper caps, though, I don't waste time troubleshooting on them, I just replace them. Many are leaky and placing a capacitor in Parallel with a leaky one won't do any good.
: By the way, you are right about paralleling capacitors. Their capacitance values add in parallel, but not their voltage ratings, so if you parallel a 0.01uf and 0.005uF capacitor you get 0.015uF at the voltage rating of the lower voltage rated capacitor.
:
: Best Regards,
:
: Bill Grimm
:
:
Thanks Bill,
Advice well taken, I will replace the old paper caps's as well as the E's.
Mitch

Hi Mitch,

You may want to check this out.
http://www.avorex.com/PaperWax/Paperwax.htm

Best Regards,

Bill

I have read this as well. One book comes to mind that is written by David Johnson. This is a useless practice, as paper capacitors rarely open up, and paralleling capacitors will only reveal open capacitors. It will do no good (no improvement) if a capacitor is leaky. It is best to replace paper capacitors in critical areas--where they are subjected to over 50 volts, and/or are in a high impedance circuit, such as a control grid or AVC circuit. This type of circuit is very sensitive to leakage that would alter a very low current voltage. High voltage circuits are also problematic because paper capacitors often develop leakage, and high voltages leak and/or arc through this leakage very easily. You do not need to replace paper capacitors that are across cathode bias resistors, though you may if you really want to.

T.