You might be wondering what this strange contraption is. This guitar came for a clean up and the owner had concerns if everything had been wired correctly. Housed under the jackplate is an active preamp system for the pickups, with an on/off switch. I'm not sure if it was previously installed, or made for OEM - I emailed Dimarzio for some information about it but I never did receive a reply >:| Maybe no one there knew what it was either haha.
Since the jackplate was falling apart, the electronics needed to be rewired, and the owner didn't like the plate anyway - we decided to replace it with a conventional strat jackplate and move the preamp/battery housing to a different location. This required a total rewire of the preamp/switching system, as well as the rest of the controls - and a custom route to house the preamp.
As you can see in the first picture, the wiring was a MESS! So I started from scratch, replaced all leads, re-routed the controls so that one of the pots with a push-pull switch would operate the preamp on/off switch. After routing the back out for a traditional 9-volt battery box (pictured below), I installed the box & wired the leads to the back for easy battery access. It was also the only place we could have put it with all the other body cavities existing.
Finished product below shows traditional jack plate installed, tone pot with push-pull preamp operation, and battery housing installed next to the tremolo spring cover plate.