if you've wired it straight from the battery to the stero jack and the pickup, with no pots in between, and then changed the jack and your still getting the problem, there is one of 5 things going on:
1. You ruined the pickup doing something
2. The pickup came to you broken(Which happens, there is an accepted ratio of good product to bad product at any factory)
3. something from the guitar to the amp is messed up (See: Cable, input jack on amp)
getting distracted, someone watching attonement on the PC next to me.. I love Keira...
ANYWAY
4. Something inside the amp is broken
5. Nothing is broken, and the Entire World is out to get you...
Anyone who knows electronic troubleshooting(car mechanics included) will tell you the best way to test fault is either to have the entire correct setup, remove a item, and retest untill the signal clears showing the issue. Or remove everything but the bare esentials and add until failure.
If you keep buying batteries and electronic parts you have allready spent as much as a cheap meter. You can get one at home depot, Lowes, menards, Radio shack, HEB, etc. for about $15
one with a Tone is best IMO because you dont have to read it, just hear when the signal is clear, but any will work.
Your post are very confusing, and I dont think anyone means to insult you, but you are posting multiple times in the same hour going back in forth.
from your first post, the capacitors I use have 1.5 inch legs, so when bent, it almost reaches 3" from wherever I have it soldered, my pots are usually less then this. If a instance occured, I would just extend one leg using a wire.
this is a confusing statement. The amp sounds like feedback, even when the guitars not attached?!?!? Theres your problem. sounds like the wire is using YOU as a ground, DANGEROUS AMPS ARE HIGH CURRENT!!
OH SNAP! She just jumped into the fountain...
anyway..
THEN you wrote that you tested using a passive pickup, and get the same issue..
either your amp is busted, or your doing something wrong if the PASSIVE wired straight to a jack is bad.
one thing you could test, is bypass the stereo jack and wire the battery directly, this will keep it "on" but take it out of the circut, then see if it outputs signal. If not, then its time to Call EMG.