Hey guys! With a name like Rickenbackerman I just had to chime in.

This is a great thread!
About the extra capacitor and what it's for - I hadn't seen the reason posted yet so I thought I'd let you guys know. This info is from Mark Arnquist who is a certified "Rick guru". The extra cap is there to increase treble on the bridge pickup. That's all, nothing more. Volume is increased when you remove it, but that's just a side effect. The reason to increase treble on an already twangy bass is because it was originally designed for use with flatwounds, which are inherently duller-sounding than rounds... But when they redesigned the 4003 for use with rounds, they removed the cap...
Also, for anybody out there who has truss-rod problems with their older 4001's (stipped nuts, bent rods, whatever), Mark Arnquist has a solution. It takes a little machine work and some general "handyman" skills, but I did the mod to the rods on mine and the rods now function flawlessly...
Visit Mark at the rick forums!
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I've got a '79 4001, and it's a workhorse! Bought it for $200 with a broken headstock, no bridge, and no bridge pickup. Fixed the break, threw a badass and a set of bartolinis in it (yes they do rule!) and it thumps like no other! It's got a chipped, dinged, and generally molested burgundy auto-body shop respray, but doesn't look bad from more than 10 feet away! LOL $330 invested!
I used to have an azureglo (blue) '78 which I sold a few years ago for $500 because I needed the money. (banging head against wall) Stupid, stupid, stupid!