Substituting parts in a Marshall Guv'nor

[rhys]

I have two part sub questions.  The pedal is a Marshall Guv'nor.  Here's a link to the schem:  http://www.generalguitargadgets.com/pdf/ggg_mgv_org_sc.pdf

FIRST, can I sub a 1k resister for the 680ohm in R10 or will that greatly affect the tone?

SECOND, I don't have a 220pF for C8.  I do have several small value silver mica caps.  I've read conflicting information on how these are coded though.  I have the following:
one which is coded 100;
several coded 390;
two coded 82J
and one coded 500.

I'm sure none of them is a 220, but I don't know whether the 500 is 500 pF or 50 pF; or if the 390 is 390pF or 39pF, etc. 

Which would get me closest to 220pF and will it matter? 

Thanks,
Rhys

[foxfire]

you should be fine with the subs. if you have them use sockets so that you can either later replace them with the "correct" part or try different subs.

[BubbaKahuna]

For the most part, tiny caps that only have a number value with no numbers are the value in pf.
http://www.unitconversion.org/unit_converter/electrostatic-capacitance.html will let you convert that to other values (nf, uf, whatever).

I can't remember where I found this, but I use this chart for the codes:



Save it to your HDD, I can't promise the image will be available forever.

***  Remember, you can increase capacitance by running caps in parallel. ***
A pair of 100pf caps side by side will give you 200pf. Considering the tolerances are probably only within 20% anyway, that's close enough for a 220pf.

Cheers,
- JJ