BOSTON Msubwoofer schematic?

newbie just opened my used Msub... no boom from LFE or line-level.
BIG *** transformer is sending 40V and 170V to the amp PCB, nothing melted. Woofer ~5 ohms DC, not open. Suspect pre-amp side (another PCB).

Does anybuddy have a source for the schematic, or recommend a shop in Detroit area for reasonable repairs?

BA sells the "amplifier" for $199, which means I would have ~$300 total invested..............

please & thanks,