Fender Player Plus Jazz with East Preamp - Wiring Question

[FatDrunkStupid]

I recently purchased a Fender Player Plus Jazz bass (active). I bought the bass because I loved the weight and feel of the neck - I knew the stock preamp would be an issue, mainly because of the lack of a passive mode and, as I'd been advised by several people far more experienced than myself, the preamp isn't particularly great. This wasn't (isn't) a problem because I had an East J-Tone preamp ready to install. I knew that this would make the side jack socket redundant but I assumed I'd be able to use the existing dual battery compartments (original preamp is 18V) as I knew the East preamp would work at either 9 or 18V.

 

Upon opening the bass up, I found 2 wires coming from the battery compartments (black/red). Great! I can just remove the 9V battery clip from the East preamp, connect the existing wires (black to black, red to red) and all would be fine, right? Nope, with this setup there's no output. After checking ground connections etc. I reconnected the original battery clip, connected and dropped a single 9V battery into the control cavity (as per the East instructions) and lo, everything works fine.

 

So I have a fully operational bass with a great sound but I still want to utilise the dual 9V batteries. Yes, I'm a total electrical doufus and I apologise in advance for this fact. The photo below shows the current setup with a single 9V battery and the original battery wiring emerging into the control cavity top right (circled). What am I missing here? Was my initial wiring assumption waaaay too naiive? Should I stop right now and hand it over to someone who knows what they're doing? All advice and insults received with appreciation!

 

[itu]

A basic question: is red positive? Are you sure?

[FatDrunkStupid]

8 minutes ago, itu said:

A basic question: is red positive? Are you sure?

Nope, I don't have a multimeter. If I try the wiring reversed, am I likely to hurt anything?

[paul_5]

Yes, potentially. There might be reverse current protection on the board, but I’m not sure. Check first.

 

 

also, if you plan to run the unit at 18v you’ll need to connect the batteries in series.

 

Edited July 2, 2022 by paul_5

[Woodinblack]

Are there two good batteries in the original compartment?

[FatDrunkStupid]

@paul_5 Thanks, I'll check that.

@Woodinblack Yes, the batteries are brand new.

[Aidan63]

Just a suggestion but I would contact John East and ask him the ebst way to wire it, he'll tell you

[FatDrunkStupid]

Closing the loop on this one in case there's someone else out there as clueless as me (unlikely). @paul_5's diagram pointed me in the right direction. In my case, the +/- battery link was broken. A quick resolder and everything's working fine. Thanks for everyone's help.