OK. So, the Stingray is back up and running! I took it to the electronic wizards at HATCH Guitar Works in Modesto, CA. Turns out that the battery change had blown the op amp on the PCB. Luckily, the PCB is the older, hole through kind. Quincy Hatch just unsoldered the op amp, put a little plug in module onto the board and added in an updated op amp. He also added some kind of diode (I think that's what he said) to protect from spikes. The evaluation and repair were significantly less than purchasing even just a new board. The bass sounds great again.
If you are in the Central Valley and need an amazing tech, check out HATCH Guitar Works and effects. They make some killer pedals as well. One allegedly can even mimic the sound of a Dumble amp. I have never hear a Dumble, so I have no idea.
Very happy to have the Stingray back in rotation. These guys were first-class all the way. Hooah!