Hi Jim,
I can't really help with the first issue - but the MAG series is solid state, no valves involved.
The VU meter at the front is really just to show the input level of the bass into the preamp, and the red section is there to illustrate when the signal is too high for the preamp to cope without distortion
When you say the light gets dimmer - is the sound affected? I can't see any reason why the power of the light on the VU meter should be in any way connected to the input or output of the amp, as it is just that - a light.