how can I identify these capacitors?

[dann]

I'm sure this is an amateurish question, but I'm new to this.


I'm trying to mod out my guitars a few different ways. I have some capacitors I'd like to replace, but damned if I know what I'm looking at.

One is a small tan one marked "251", and the other is a larger green marked "2A393K"

If someone could tell me what I'm looking for/what to orde rit'd be greatly appreciated. Also, is there a way to tell so I won't have to keep asking? I was told that brown one might be a 250pf, but that doesn't sound right for a guitar, does it?

thanks!

[greekie]

251 is usually a 250pF - from your description it sounds like a ceramic capacitor - those are found in guitars, as high pass on volume controls, so your sound won't be muddy, when you turn down the volume. The other cap you need to disect the numbers. 2A means "two times the voltage rating of A", which is as far as I remember 50 volts - 2x50 = 100 volts cap. 393 is just like the first number. 39 with 3 zeroes after it = 39nF capacitor. K is the tolerance - again, from a distant memory, I think it's 5% or 10%. That cap must be in the tone circuit.

Hope this helps.

[dann]

Thank you. How would I express those as Uf? That seems to be the standard when ordering new caps

[greekie]

1nF = 0,001uF - u is micro, n is nano and p is pico - denominators for 1/1000th of the latter.

[Albert Kreuzer]

What greekie said.
Some examples:
251 = 250pF = .25nF = .00025µF
102 = 1000pF = 1nF = .001µF
393 = 39000pF = 39nF = .039µF

HTH

[dann]

so the tan one would be 0.25uF, and the green 0.039uF?

[dann]

oh i was way off. math's never been my strong suit.

[dann]

Also, I'm seeing some caps expressed as MFD. What's that?

(again, sorry for all the amateur/rookie questions

[Albert Kreuzer]

No, 251 is 250pF, that's 0.25nF, not µF.
MFD is an old name for µF (micro-Farad), whereas mF stands for Millifarad (1000µF).

[Enzo]

Millifarad would be a legitimate unit, but I have never seen millifarad rated parts in anything, certainly not guitar amps. So what Albert said, MFD or mfd would be old style ways of saying uf. Much rarer would be ufd, though some drawings did use that style. And on old schematics, what we now call pf for picofarads, would have been called uuf for micro-microfarad, and before uuf was mmf.