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HELP! Mysterious electronic problem cutting output

Discussion in 'Pickups & Electronics [BG]' started by codyvir, Oct 23, 2013.


  1. codyvir

    codyvir

    Mar 14, 2013
    Arlington, VA
    Hey guys,

    Long time listener, first time caller, and I really need some help. Here's the problem:

    I have a Warmoth Jazz bass that I bought used, and it has been awesome until recently. It has Seymore Duncan SJB-2 pickups and an older Audere JZ preamp (from the first couple of years they were building them). The trouble is that I plug the bass in, and can play it in all its glory for about 30 seconds-a few minutes before something happens and the power output suddenly cuts significantly, and it seems that the tone loses some of its definition. It doesn't always seem to take the same amount of time, but it always happens. It will happen even if plugged in and left laid flat on a table and not touched (with volume on bass and gain on amp turned up high so I can hear what's going on).

    To try to fix this I have:

    1. Replaced the battery

    2. Replaced the input jack

    3. Replaced the wires from the battery box (It seemed that there was a bad connection there somewhere, with some of the wire a bit worn and stressed from where the battery box opened and closed [a problem with some of the flip-out types]. Also, that wire had been joined in several separate sections - leads from various components to wires connecting to leads from other components - so I thought to cut some of that out.)

    4. Foil-shielded the cavity while I was in there, just for good measure. I did this with aluminum tape, connected the cavities with wire, and a wire to the bridge for ground (where the other ground wire is). It was a bit noisy, and from the few moments of good playing time I get it seems to help that issue.

    5. Gently stroked its headstock and told it sweetly that it was my favorite, and that those two new P-basses I just got were nothing to be jealous of, and that it was the one I wanted to play at my gig on Friday.

    Is there still some kind of power issue from the battery to the preamp? I'm pretty sure my soldering is good (not 100%, but the joints look OK, and it does make noise). Is there some kind of grounding problem, and if so, how do find/test it? Is my preamp fried? Could it be an issue with the pickups?

    Thanks!
     
  2. almost certainly a dry joint in the preamp - often they're easy to spot as they look kind of 'dull'. Probably a capacitor junction if the tone changes. A quick re-flow of the solder with a small tip, hot iron will cure it.
     
  3. khutch

    khutch Praise Harp

    Aug 20, 2011
    suburban Chicago
    I guess I would set the bass up with the control plate opened up so you can easily access the wires and the pots and the preamp board. Then power it up and wait for the dropout. When it drops out take the eraser end of a pencil and poke around, move wires, etc to see if you can find a wire, a pot, or a location on the preamp board were moving or tapping can restore the output or better yet make it come and go. Then you know where the problem is and maybe the solution will be obvious. I suggest a pencil rather than your finger merely because a pencil is smaller and better able to localize the problem. But your finger could work too.
     
  4. codyvir

    codyvir

    Mar 14, 2013
    Arlington, VA
    OK. Thanks. Any other suggestions on how to find the offending spot? Found this pic online of a similar unit:

    JZ3-web.

    My thought is that somehow there is a problem with the power input to the board (the red wire from the battery straight to the board. That did seem to be a bad connection, and when I was changing the input jack, it broke off completely, so I did resolder it. Perhaps I should check that spot again.

    Also, why would it come on at full power, then drop out, but not come back? If I unplug the jack and plug it back in, it comes back on at full strength, then drops out again. That's what puzzles me most. If it were only a physical connection issue (which it may be, I'm certainly no electronics whiz), it would seem to me that unplugging the cable and plugging it back in wouldn't in itself change the state of the connection, or explain why it initially has full power then drops out, or why, if it goes from good connection to bad connection, why it wouldn't be just as likely to come back around?
     
  5. codyvir

    codyvir

    Mar 14, 2013
    Arlington, VA
    OK, so, I think it's fixed. It looks like the power connection to the preamp board was the culprit. It looks like what happened was that the wire was soldered to the little copper surface connection point just fine, but that somehow the surface point itself was making a poor connection, as when lightly prodded that wire the problem would occur, and then when I tugged at the wire a bit (gently), the whole thing came off, surface connection and all. By dropping a tiny bit of solder at that point, and then tinning a freshly-trimmed bit of the wire itself, then connecting the two spots, I think i now have a solid connection. I'll have to just wait and see if the connection holds up long-term. Thanks for the quick help!
     
  6. codyvir

    codyvir

    Mar 14, 2013
    Arlington, VA
    So, Nevermind. The problem isn't solved. I thought it was, but didn't have time to really test it out. The problem still remains basically the same, with the bass playing perfectly initially, then getting some crazy distortion as if the plug were not seated properly, then playing very quietly. If I unplug it and plug it back in, the cycle starts over again. Ideas?
     
  7. ex-tension

    ex-tension

    Jun 11, 2009
    Sounds like a problem on the preamp circuit. I don't think it's a problem of connections. Probably an electronic component (most probably a capacitor) on the preamp is faulty.
    Try to talk to Audere and see if they can help.
     
  8. uOpt

    uOpt

    Jul 21, 2008
    Boston, MA, USA
    Sounds like a capacitor gone bad to me.

    Did you try the pickups without the preamp yet?
     
  9. codyvir

    codyvir

    Mar 14, 2013
    Arlington, VA
    I did call Audere, and spoke to a gentleman who was incredibly kind and patient, but unable to do a whole lot for me (in DC) from Oregon. I'm a stickler for good customer service, and I've gotta say that I received all the help that I could reasonably expect and more.

    I have not tried the pickups without the preamp yet, as I don't have everything on hand that I need to wire it up passively (spare pots, etc.), but I'd planned to try that tonight. Is there an easy way to test them without completely rewiring the bass?
     
  10. ex-tension

    ex-tension

    Jun 11, 2009
    Diconnect the pickups from preamp, then connect them to the output jack one by one and play. No need to connect any vol or tone pot.

    Isn't there the option of sending your preamp to them for inspection?
     
  11. codyvir

    codyvir

    Mar 14, 2013
    Arlington, VA
    So, after testing the pickups and finding that they were fine, I made one more go at checking the preamp wiring, and could not get it going. I called Audere back and asked the gentleman who answered about getting a new preamp. He asked me since more questions about the issue, helped me figure out that one of the internal traces from the wire connection to the board was damaged, pulled out the schematics of the board (which he had designed) and found a place where a wire could be soldered from the battery to a diode to get power to the board. This worked, but I was clumsy and ended up pulling the diode off of the board.

    So,

    (a) it was in fact a power-to-board issue
    (b) I botched the last-ditch repair effort
    (c) I ordered a new model unit to replace it

    In the mean time, it is wired passively. A quick fix was needed, because I have a gig tonight, but I can't wait to get the new Pro JZ-3 next week!

    Finally, I have to say that I don't think that I have ever, in my life, had a better customer service experience than I did with Audere. The quality of their product (when not damaged by an idiot), and the kind of attention that I got (it was the founder of the company, I came to find out, who answered the phone and helped me) have won a sincere advocate for life. He could have just told me it was hosed from the get-go, and not wasted his time, but he didn't. #1 A+ First Class people to deal with.

    Thanks for all the help!
     
  12. ex-tension

    ex-tension

    Jun 11, 2009
    I see you ordered a new preamp. But I think there is still hope for the damaged one. I don't know this particular preamp and it's circuit. But if there is a diode at the power input it's there for reverse polarity protection. See the circuit at the top of this page:
    http://www.instructables.com/id/Reverse-Polarity-Protection-Circuits/

    If you connect the same battery wire to the other side of the diode you still can power the board but without the polarity protection.
     
  13. khutch

    khutch Praise Harp

    Aug 20, 2011
    suburban Chicago
    Most likely the diode could be replaced too, on the board or in line with the battery feed wire.
     

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