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A question about active systems

Discussion in 'Luthier's Corner' started by tjclem, Jul 4, 2004.


  1. tjclem

    tjclem Supporting Member Commercial User

    Jun 6, 2004
    Central Florida
    Owner and builder Clementbass
    I built a bass with an active set up. I put it together without any finish on it and it sounded great no problems. I stripped it down put the finish on it, shielded the control cavity and put it back together. It now has a nasty buzz when you touch the knobs. Should I not shield the cavity? The only wires I had to solder were the shielded set from the Bartolini "P" style pickup
     
  2. Josh Curry

    Josh Curry

    May 29, 2003
    Frisco, TX
    Do you have a ground wire hooked up to the bridge?
     
  3. tjclem

    tjclem Supporting Member Commercial User

    Jun 6, 2004
    Central Florida
    Owner and builder Clementbass
    Yes. I just figured it out. When I was tightening up 1 of the pots it swung around and touched the shielding in the cavity. I do have another problem though. The pcb is loose in the cavity as is the battery. I just took some thin foam and wrapped it around them so neither ground out. I would like to figure out a better way of isolating them..................t
     
  4. Josh Curry

    Josh Curry

    May 29, 2003
    Frisco, TX
    you can get metal battery clips from radio shack or other electronics store. I know Fry's has them, if you have one of those near you. Is the PCB in one of those black cases? If so I would just use some double stick tape and stick it to the side of the cavity. Otherwise, I've seen them attached to the leads of one of the pots, but I think that's a custom thing. I've also seen battery's attached using velcro that is hold by a single screw to the side of the cavity. Of course the poor mans solution to all of these is just wrap both in 1/8" foam and let it float in there.
     
  5. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    LOL. Yeh, I shielded 3 cavities and couldn't tell any benefit that resulted but they make great conductors. Haven't shielded a cavity since.

    The main thing with the battery is you don't want it flopping around - esp. into the PCB. So it depends on the space you have. If it's a snug fit, like I've had, I just made a jacket out of thin foam packing wrap. The battery clips I've had exposure to were too snug a fit and there was more potential damage to the control bay from removing the battery than anything - so I got rid of the clip cause I used rechargeables and I was always changing batteries, back when I had onboards.

    I've only had one occassion with a PCB board not mounted to pots and I just took a small (like 2 x 2) zip lock bag that came with pup springs, slipped it over the board and sealed the bag up to the wires. I didn't tape it down cause it wasn't going anywhere anyway, but it wouldn't hurt. If you have any interference problems you may have to shield it. I just recieved an '87 UK Status 2 band in the mail and it actually was wrapped in copper shielding. But I personally wouldn't stick anything directly to that PCB.
     
  6. tjclem

    tjclem Supporting Member Commercial User

    Jun 6, 2004
    Central Florida
    Owner and builder Clementbass
    Just took the bass to an open jam last night and it still had the problem, not as bad though so I am getting rid of the shielding today and I 'll try playing it without it..........T
     
  7. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    I think you may be better off. Not sure how effective the shielding paint is but it won't ground components out. An alternative to removing it is to lay a strip of electric tape below the lugs of each pot just to insure there's no contact there, since that's where it's most likely. That's what I did. But you have to keep the lugs of the pots from contacting the sides as well (or throw a strip of electric tape there). I didn't have any problem with mine but if you ever do have a problem, it makes trouble shooting more of a pain cause the problem could literally be anywhere.

    It took me hours to shield those stupid things and I wasn't up for ripping it out as a result. It does look cool and professional though.

    By the way, cool looking bass.
     
  8. tjclem

    tjclem Supporting Member Commercial User

    Jun 6, 2004
    Central Florida
    Owner and builder Clementbass
    Thanks I will get to jam with it again tomorrow evening.......t