What is the chip in the middle?
I don't know because I am not currently in possession of it. I was hoping it would be documented somewhere online (thus the post). The chip data/specsheet is what I am looking for.
Looking for static DC voltages on certain pins is a clumsy way to troubleshoot
It might be 'clumsy', but it does help, if you know what you're looking for. In my opinion/experience. If you have more specific/targeted suggestions in this specific area, I'm open to them.
Malfunctioning how?
Described to me as "it doesn't work that great". The output through the amp is super quiet/low most of the time if I remember the description correctly, so my hope is a bad wire/solder joint.
The first thing you or whoever is giving the bass away tried is replacing the battery, right?
Yes.