on your jack, you see the 2 metal tab sticking out? One taller, one shorter?
The taller one be your +(tip, aka signal path), the short one is your negative(sleeve/ground), this tall and short fella is part of the 2 metal point with holes where you solder the wires(signal and ground) to
you mentioned that the red wire was disconencted from the jack. What you can try now,
1) Connect a cable from the jack to your amp, AMP AT LOW VOLUME
2) Stripped off bit of insulation from the red wire, exposed the bare wire
3) touch either small point on your jack(theres only 2, either positive/tip/hot signal or negative/sleeve/ground)
4) If the bare wire is touching the "tip" point on the jack, you shud be able to heard your bass being amplified(provided the problem is with the jack and not anywhere else)
5) If the bare wire is touching the "sleeve" point on the jack, you wont hear anything amplifed, coz the signal is being short to ground.
try the above first and see if it work..