I know of two versions of the BA-3000.
One has pass-through solder joints (vias) on the amp boards.
They need to be checked and repaired if you have that model.
You need to pull the amp blocks and unsolder the output connections and split the amp block to get to the boards.
Once there, if you have the vias, you need to suck the solder out of them, make a short piece of copper wire to pass through the hole, scrap a little coating off the trace on each side, insert and bend the copper wire to the bare trace and solder it in.
The other type amp did not use the vias.
I typically start trouble shooting an amp blowing fuses by checking the output transistors, drivers, pre-drivers, working backward through the amp transistors. To get to the output transistors, you need to get into the amp blocks, a good time to fix vias if they are in there.
Beyond/beside that, you'll need to get a dim bulb tester rigged up and start testing voltages. Since accessing the outputs is such a pain, you're probably better to attack this from the voltage trascing route.
Do you have a decent soldering station? Solder sucker and/or wick? Digital multi-meter (DMM)?