amplifier

I've got 4 Accusonic/Show amps (2 x PSA-3900, 2 x PSA-31500), all four of them were working in all modes (stereo, bridged, parallel/mono). The following day I was testing them out and all of a sudden all four amps only work in bridged mode but not stereo mode or parallel/mono mode. Has anyone ever seen or heard of this before? I'm testing each one on their own so it shouldn't be a power supply/voltage drop issue. The only thing the four of them had in common is that they were all plugged into the same power bar running through a DBX Driverack PA2.

This hasn't happened, however, I was wondering: Suppose I have a powered speaker, like Yamaha, QSC, etc. The amp in the speaker dies, or stops working for whatever reason. If that were to happen, could the speaker be powered via an external amp, and be used like a normal passive speaker? 

Linea Research have released the latest and most powerful member of their 44M family: the 44M20. This has the mind-boggling specs of four 5KW power amplifiers in one 2U 13Kg chassis, designed for touring companies where subs have to be powered and fed independently from the mids/tops. Its main input is rated to work from 85V to 250V, although by my quick calculations the mains current draw at 85V would have be around 250A for all channels at maximum output.