when the tech opened up the bass did you notice if the cavity was shielded? Usually they are, with copper "tape". If those aren't shielded, then that is something you can do to greatly reduce humming buzzing and other unwanted noise (your playing style not withstanding hehehehe). Make sure ALL cavities, i.e. pickup and controls, are shielded, and that all of the shielding is grounded to the body ground. You can go onto youtube and search guitar shielding. There is a whole herd of videos with guys showing you how to do it.

IIRC those basses have EMG-HZ pickups(high impedance passive), if you switch to the active pickups( low impedance) like your Guild bass that issue should be taken care of.

I have had similar issues with other basses that had the EMG-HZ pups.

I'm sure Bo had a similar problem at some stage. He'll check in shortly no doubt.

I'd almost be willing to bet that it's more of a sizzling sound than an actuaI 60hz hum. I had the same issue with my Spector. I'm about 90% sure that all Korean basses from that time period used the same preamp (especially those with EMGHz pups--strictly assuming here--LOL!). My Spector and your Schecter are about the same age.

My first impression was a bad ground, cavity shielding, etc but what I figured out was the treble circuit on those mass produced Koreans is pretty hot and I'm thinking the Hz pickups just simply do not play well with them.

I pulled the stock preamp, dropped in an Aguilar OBP3, and replaced that neck Hz with a Seymour Basslines Jazz QP. I also keep my treble top dead center (the middle). Now, my buzz is strictly the single coil type--I never use the bridge pickup--and honestly it's not bad at all. I play it live every Sunday under the lights (that includes a fluorescent reading lamp on my music stand) and with a full band. I've also done some studio work and found it to be very quiet depending on how I'm positioned.

I play it everywhere. Before, I used my T40 or Stingray for stuff when I was worried about hum but now I'm pretty much using that Spector for everything.

So here is my suggestion--two suggestions actually--ditch the stock electronics and upgrade or simply cut the treble knob back. My bass still gets plenty of treble bite even with the treble knob set flat. Good luck to 'ya!

--Bo