Hum or buzz in my century standard
 

Just got my used century standard and it has a hum or buzz that goes away when the treble is turned all the down or the blend adjustment is full to the neck pickup. What to do?

Actually it does not go away when I pan to the neck pickup but it does reduce. The hum/buzz does not go away by holding the strings.

Bummer Doug.
It's probably related to a ground or shielding. I'd start by pulling the output jack and verifying that none of the wires are touching each other or the shielding paint on the jack cavity. The jack should have some heat shrink on it. Also make sure that there aren't any sharp or pointed solder joints sticking out through the heat shrink.
If nothing looks suspect there I'd ohm out all of the ground connections with a VOM and check to makes sure that none of the pot terminals are coming in contact with the bottom of the shielded control cavity.
It could also just be a bad (or dirty) pot. You might want to get some tuner clearner, spray a bit into the pot casings and then work the pot shaft back and forth.

Good luck and don't get discouraged about it. Worst case is you need a new preamp.

This is almost certainly a issue based on either a ground fault or loose wire allowing stray signals to enter the signal path.

Unfortunately, once a bass leaves the shop, it gets bumped and bounced, and sometimes things will shift and cause this issue.

The good news: it's really simple to fix.

Your dealer or local repairman should be able to quickly isolate and identify the issue and resolve it, if not please contact us and we will be happy to help.

Sorry you're having trouble!

Thanks Gard, I'll check this out.

I checked out the wiring and it looked perfect and very well done. Impressive. I talked to San Diego Bass on this and they said that they would pay to have it shipped to you.
With a little more investigation, I found that the humming would go away if I held the bass horizontal to the floor and the amp. I then tryed out my L2000 and found a little hum also.
I sit right next to the amp when I practice and when I adjust the settings on the guitar to the sound I like I can only very very faintly here a hum. I think I'm over this...
It is an 18v 5 string and my other basses are 4 string 9v or passive.
Thanks for you attention to this concern.
Customer service from Bass San Diego and Roscoe was excellent.

Sounds like a grounding/shielding issue, could be tricky to isolate, and COULD actually be outside of the instrument (i.e. house wiring, or an issue with your amp, unless you have eliminated these as potential sources by trying other amps/locations).

We will be happy to look at it, if it begins to be an issue for you. :)