when do you need to replace Fender filter caps

texwest · Post by **texwest** » Sat Dec 03, 2005 12:09 pm

Thanks for the explanation Dan. That was very helpful and simple. I don't want to know everything, just enough to work on my amps.

Is this correct? Are mfd and uf equivalent? I undrstand that 1uf = 1000nf = 1,000,000 pf but the four section can says mfd on it. I'm assuming that mfd is the same as uf?

Is there a simple explanation of the function of a cathode bypass cap?

Wes

novosibir · Post by **novosibir** » Tue Dec 06, 2005 5:39 pm

texwest wrote: Is this correct? Are mfd and uf equivalent? I undrstand that 1uf = 1000nf = 1,000,000 pf but the four section can says mfd on it. I'm assuming that mfd is the same as uf?

1.0mfd = 1,000uF = 1,000µF = 1,000,000nF = 1,000,000,000pF

Larry G

novosibir · Post by **novosibir** » Tue Dec 06, 2005 5:50 pm

texwest wrote:Is there a simple explanation of the function of a cathode bypass cap?

A cathode bypass cap enhances the amplification of a tube stage from a definite frequency point onwards for about +6dB

If the cap is maybe 22µF or bigger, the "point" is lower than your deepest note on your guitar.

If the cap is .68µF or 1.0µF, only the mids and highs will be enhanced.

There of corse are formulas, but better use your ears to select the "right" one, because the "point" of enhancement also depends on the values of the plate resistor, the resistive load after the coupling cap and the value of the cathode resistor.

Larry G