Looking at the schematic, and the four 3055 output devices as well as the lousy heatsinking, it's 150 watts RMS would be at 4 ohms, not 2 ohms. There is no protection for shorts, or overheating as with modern amps. At 2 ohms, the power amp would try to develop more power than the components are rated for.
The power amp is the same as the power amp in the Concert Lead and Concert Bass amp. You are right, info is sparse.