Annoying hum and how to get rid of it

[jbednarski]

Wondering if anyone has any concrete information they can share with me about electrical hum coming from one of my basses.

I recently picked up a Squier II Precision from the 80s. Incredible neck, plywood body I'm guessing but a really great, cheap bass. I'd been wanting something inexpensive to leave at work to practice during lunch and this fit the bill perfectly.

So when the bass arrived I noticed it needed a set up badly and had a very loud hum that wasn't affected my my touching or not touching the strings but got louder when I turned the tone control up and went away when the tone was in full "bass" position. When the bass was parallel to my amp it was quiet but in a perpendicular position the hum was present.

So I did a new set up, installed new DR Lo Riders, shielded all the cavities and connected them together and repositioned the bridge ground wire. Now it's almost perfect except the hum is still there but a LOT quieter than before but still noticeable enough that I'd like to get rid of it.

The pickup is fairly low in output and I'd like to replace it but not with one that costs more than the bass itself. So I'm wondering if the hum could be caused by the pickup or the tone pot (both pots are 500k-ohm).

Before taking it to my tech (and again spending more than I'd like to on this bass) I was wondering if anyone had any ideas on this. Thx!