Not a pedal question- bass w/ active pickups draining batteries

[Ponchus]

Hey all
I know you all are technical wizards, so I figured I'd post this question here, even though it's not stompbox related. 

My bass player has a fretless bass with active Bertolini pickups. He had some problems with it, so he sent it back to the manufacturer (since it was still under warranty at the time). I believe that one of the issues he was having was a broken jack. I don't think that any of the other issues were electronics-related.

He received the bass back from the manufacturer, and it seems that now the bass is draining batteries at a ridiculous rate. He'll put in a brand new battery, play it once, unplug it and put it away, and the battery will be completely drained within a week or two (of inactivity, mind you, and unplugged). He brought it into a repair shop by his house, and they didn't find anything wrong with it (though who knows if they jerked him around and didn't even look at it- they're kind of a bunch of jerks, honestly). He can't send it back to the manufacturer at this point because the warranty has now expired (and he now doesn't trust them). So he asked me to look into it. However, I don't really know what I'm doing. While I've built a bunc of stompboxes before, based on layouts here and on Tonepad and GGG, I've never worked on guitar (or bass) electronics. Any ideas on what to look for?

Thanks for any help 

[cd]

I bet the input jack has been wired so the active circuitry is hardwired "ON" all the time.  Go this link and scroll down, it will tell you how to wire a stereo input jack to turn power on/off.

http://www.diystompboxes.com/cnews/FAQ.html

[Ponchus]

Yeah, I figured as such, since pedals are hardwired the same way. I received the bass last night to take a look at, but won't have a chance to take a look at it until tomorrow, unfortunately. I figured that I might as well ask you guys in the meanwhile, in case there's something else that might be going on. The thing that worries me is that if the circuit were hardwired to be always on, it should be pretty obvious, and I can't imagine a decent repair shop not catching that mistake immediately.

[petemoore]

  Yupp, sounds like a perfectly reasonable scenario, CD. If the battery 'was' strong and 'just sat' for a time and lost juice...the battery must not be getting disconnected.
 Something worth looking at anyway...probably moot if the device is working properly...
 You could measure the current draw...with the DMM between the battery and the circuit...pick a battery connection and clip one side on [turn the clip 1/4 turn] then run the other side through the DMM set to an appropriate Ma setting.
 I bet the circuit design call for modest to very small current requirements, something between 3ma and 10ma...please correct me if I'm wrong...anyway...that's one place to look.
  And of course if the current draw doesn't drop to nothing when the bass is unplugged...that'd mean the battery is staying connected regardless.

[Mark Hammer]

Do you have any idea how people here have inadvertently soldered the black lead of the battery snap to the *wrong* lug on a stereo jack? 

It doesn't take stupidity to do it either.  All it takes is using a different brand of jack than you're used to, and flipping the jack around the other direction so you can hold it while you solder with the other hand, and bingo! you've lost track of which lug connects to which contact.  The first sign is when you go to use the device the next day and are greeted by the same thing you describe; "Say, I thought I put in a fresh battery yesterday.  What gives?"   I've done it more times than I care to think about, with pedals, active guitars, etc.  It's a serious bummer when you do it with a pedal using a bipolar +/-9v supply.

[Ponchus]

Great...well I was guessing that the jack was just wired wrong, and it seems as if you all concur. I was worried that maybe something else might be mis-wired that I should keep an eye out for, but it seems perfectly plausible that the jack is the culprit here. I'll check it out and repost if anything out of the ordinary comes up.

Thanks for help!

[Ponchus]

Hey everyone
I have one more question to add onto this (I just spoke to my friend- the owner of the bass)...This bass has can be operated in either active or passive modes. There is a push/pull volume knob, and when you pull it out, you're in passive mode. When the battery dies in the bass (possibly due to this jack being wired improperly) , shouldn't the bass still be operational in passive mode??

Currently, tt isn't...the bass is completely useless with a dead battery. Sorry to be a complete idiot on this subject, but I've never owned a guitar or bass with active electronics.

Thanks again.

[cd]

It should still be operative, but who knows what was re-wired when it was "fixed".  You'll only know by opening things up.

[Ponchus]

hmmm, so it should be operational? So there's more here than just the jack being wrong, it seems...I'm going to have to look up wiring diagrams for this configuration to doublecheck all of this...unless anyone knows of a wiring diagram offhand?

[petemoore]

  It could be that the signal 'has to' go through the circuit regardless of the pushpullpot's position [bypass may not be TBypass]...and that is how the design works...or at least in it's 'current wiring' configuration.
  True bypass of course means" in bypass mode the wiring is effectively 'just a wire. ..bypassing everything, straight from pickup to volume control [or between vol control and output jack, wherever the DPDT or better is put]...in any case a Tbypass wiring for such an animal has advantage of enabling the bass to produce output with no supply voltage.

[Tubebass]

Some active basses I've worked on have had actual active pickups, meaning that there is circuitry inside the pickup which requires 9 volts. If that's the case, the pull-bypass switch would bypass the instrument's preamp and EQ, but 9 volts would still be required to run the pickups themselves. The last active bass I worked on, an Ibanez, had been hard-wired on as others here have described. IIRC, once it was working properly, it only used around 2ma from the battery.

[Paul Perry (Frostwave)]

If the preamp works at all, then the preamp electronics are good. I'm sure the socket has been replaced by a wrong one (and I should know, I've got a hundred or so switched jacks that switch OFF instead of ON!  ). Lots of switched jacks look identical but with radically different switching & pinouts.

[Ponchus]

Thanks guys 

As expected, the switch was wired wrong. I can't understand why the repair shop wouldn't have found anything wrong. I hooked up a multimeter and immediately detected around 1.4ma of current running without a cable plugged in.

Also, I'm guessing that the signal does pass through the EQ section the whole time, as I was able to adjust the EQ even in passive mode. Anyway, thanks for your responses.