Well, while the above answer is technically true, Fender uses proprietary jacks on many of their amps. The "4-pin, plastic" input jacks on many of their amps are a well documented problem.
I was not able to find a wiring schematic for installing the much more reliable switchcraft chasis mount jacks (you want the 1/4"(6.3mm) mono shorting type) If you do not get the shorting type of jack your amp will hum when instrument is unplugged.
If you are not comfortable with soldering on printed circuit boards you should not attempt this repair.
Brian J., April 2010
