The low B+ and the problematic voltage on OB suggest it's possible that one of the TIP50 transistors isn't mounted properly. It's also possible that you have a solder bridge between two pins of a component on the bottom side of the big PC board. When in doubt, posting pictures can be really helpful!
You definitely won't want to run the amp for very long like this, as the 107V of B+ means a lot of thermal stress is being put on the power supply.