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trying to return BB back to stock...

Discussion in 'Pickups & Electronics [BG]' started by stingray5bbx, Feb 4, 2006.


  1. stingray5bbx

    stingray5bbx

    Feb 11, 2005
    I recently added a Bartolini preamp to my Yamaha BB bass for more tonal variety. After a month I wasn't happy with the result. The +bass added more "boom" then bass and it felt like it removed the "thump" from my P pickup.. .clarity and J pickup sound was incredible.

    In the installation process I removed some wood but covered everything with shielding foil.

    Now with the factory pots and wiring.... the output is incredibly low, the 2 Vol pots only work in their upper 10% range, and the tone knob seems to do nothing. When certain parts of the pots touch the foil covered cavity, the signal dies... any ideas?
     
  2. stingray5bbx

    stingray5bbx

    Feb 11, 2005
    ok, i took the factory pots back out and measured their resistance.. and yep... for sure they do not operate in a linear scale... all the response is within 1/4 turn on both VOL and tone pots. I still dont get how this happened?
     
  3. There's nothing wrong with your pots, they're a log type pot, so they increase non-linearly (logarithmically instead). This is because our hearing doesn't perceive a linear increase in volume as a linear increase in volume. The exception to that would be your tone pot, I believe they're usually a linear number.

    It sounds to me like you've wired it slightly wrong and you're sending signal to ground through your shielding foil. I can't give you a better indication than that but that would be my bet.

    Josh D
     
  4. stingray5bbx

    stingray5bbx

    Feb 11, 2005
    Ok, i did some research and learned about audio vs. linear pots. Both VOl and the TON are 250k audio pots. The Vol pot on the active preamp was also an audio pot. But never did the bass ever respond in that "log" style... each electronic configuration still acted linearly.

    I reinstalled the pots again with extra caution of soldering and grounding. Same effect... Low output, muddy sounding, non-linear pot response and no tone control.
    When I get to 90% of knob travel in the VOL pots and all of the sudden there is sound.. there is a slight fuzz at that crossing point.

    I dont understand what the problem could be... everything worked incredible before. Is there something with teh pickups that could be causing this? endpin? Capacitor on the tone control?... I have no idea what went wrong!

    Thanks
     
  5. stingray5bbx

    stingray5bbx

    Feb 11, 2005
    help please!

    Thanks
     
  6. please post a detailed sketch of what you've done...

    it's really too hard to take stabs in the dark without a map.

    I don't even know what the original configuration is supposed to be.
     
  7. David Wilson

    David Wilson Administrator Staff Member Administrator Supporting Member

    Oct 14, 2002
    Lower Westchester, NY
    yup, photos please. You've obviously wired the stock pots / preamp incorrectly when putting them back in.
    It's always a good idea when doing these things to take pics / notes before pulling the old electronics out.
     
  8. stingray5bbx

    stingray5bbx

    Feb 11, 2005
    When i pulled the factory passive pots I left them wired together, just removed the wires from PUP, Jack and ground. Here is a quick drawing I made of the wiring.. will double check when i get back to the bass this afternoon

    Edit: uploading troubles, check back this afternoon.
     
  9. stingray5bbx

    stingray5bbx

    Feb 11, 2005
  10. David Wilson

    David Wilson Administrator Staff Member Administrator Supporting Member

    Oct 14, 2002
    Lower Westchester, NY
    sorry, without pics I can't really help too much.

    Do you have much experience with soldering before? Do you have any cold solder joints?
     
  11. stingray5bbx

    stingray5bbx

    Feb 11, 2005
    yes i have experience soldering (mostly automotive electronics) and my friend helped me who solders circuit boards for his job and he inspected it all. The joints that are not pretty are because of the factory solder, but are a solid solid connection.
     
  12. Passinwind

    Passinwind I Know Nothing Supporting Member

    Someone else already posted the answer, like as not. Don't allow those parts of the pot to touch the foil, it's grounding out your signal! Try leaving the pots wired, but remove them from their mounting holes and make sure the pots are not touching anything that's metal, anywhere. What do you get now?

    Also, your soldering technique needs some help.;) Did you reflow all the joints with fresh solder? What's the mention of "factory solder" all about?
     
  13. stingray5bbx

    stingray5bbx

    Feb 11, 2005
    The only soldering I changed was the pickup wires and jack. The rest is factory soldered. The back of the pots look bad because I resoldered the pickups grounds to them with the giant glob of factory solder that wick would not pickup.

    I know about the foil touching grounding out issue and have had the whole circuit basicallly out of the cavity and the same problems occur.
     
  14. ooohhh, mate, you need to clean up that wiring...those stray wire hairs will cause all KINDS of issues (shorts and partial shorts)...your cable jack looks particularly bad...


    Also, I have had problems before with lugs from the pots touching the shielding, rendering the pot shorted.

    Try this...

    without desoldering, pull your pots out of their holes...make a donut shaped insulating "washer" out of a disc of cardboard that is a little larger in diameter than your pot + the lugs extended...the hole of your donut is where the shaft goes through...slip this over the pot shaft...replace the pots...and if that fixed the problem, it was most definitely a short...

    for a quick test, you can just try your bass out with the pots hanging free outside of the cavity.
     
  15. stingray5bbx

    stingray5bbx

    Feb 11, 2005
    I tried letting the pots hang out of the cavity with no luck. I know the joints aren't pretty, but with much close inspection , nothing is visually intereferring. And if i try to fumble around with teh pots and wires to try to find a loose connection or make a short, there is no luck.. everything stays the same.
     

  16. 1. get an ohm-meter...use this to look for shorts (it will save you 100 hours of "visual inspections")

    2. desolder that capacitor...try the bass without the cap...now replace the cap (preferably with a new one)...make sure that the cap contacts only what it is supposed to. (one leg on the pot lug, the other to earth...

    3. check your pots...make sure that there isn't an internal short in the pots (you can do this by desoldering 2 of the three lugs and using an ohm-meter.
     
  17. stingray5bbx

    stingray5bbx

    Feb 11, 2005
    I have been using an ohm meter to check the joints, and used them to test the pot resistance response.

    I will try removing the cap - do put a jumper wire in its place or keep that connection open?
     
  18. stingray5bbx

    stingray5bbx

    Feb 11, 2005
    Ok, I took the bass to a local custom bass builder to fix the set up. Remember that I only desoldered the jack, ground, and PU wires and took the whole "pot assembly" out.

    ...He said that the cap was in the wrong place! He moved it for me and when he told me I thought... "I didnt even touch the cap...yamaha had it in place for a reason right?" I tried the bass there and everything seemed to work correctly.

    Got home and for a few weeks i've been feeling liek the sound is very uneven, harsh, and steril. I looked up some bass diagrams and found this, which is the way the wiring orignally was (although I couldn't get it to work).

    [​IMG]

    He has the Cap on the center lug and the signal on the left lug (reversed). Is this a problem? I wanted to do some research before going back and requesting he do it the way it was...
     
  19. it will work with the cap in that position, but the diagram is more the convention.

    harsh and sterile sound? from a BB? does the tone control work? get a new tone pot and a new cap...$10 worth of parts...and wire it up like the diagram.

    is the pickup selector on your BB a switch or do you have 2 volume pots? just curious
     
  20. stingray5bbx

    stingray5bbx

    Feb 11, 2005
    2pots