CDC preamp LV checkup

Following a tip-off from Lubomir that the LV reaching the preamp card might not be correct, I checked it at the board and found it to be 2.6V rather than 3V. This is due partly to voltage drop along the cable and partly to the preamp taking more current than the supply can put out. The original LV supply unit was a HPsomething. I switched it first for a Lambda LH121FM which could put out enough current (0.5A) at 3V but found this to have a wavering pedestal - +/-30 adc bins over the course of 24h, and then for a Global Specialties 1305 which is looking good after 3d. Both have more pedestal noise (pedestal s.d. ~15 bins) than the HP (~10 bins).

Things to check:

1. pedestal height - this was previously set to ch 100 - adjust offsets to bring this back to 100

ADC contents, one event (noise), first 3 are logic signals, rest are CDC prototype

1. pedestal noise and stability
2. tails from large pulses
3. gain
4. efficiency
5. resolution