  We report about the performance of the HBU0 board and the optical calibration
system QMB6 in the DESY test beam. A MIP signal was measured on the HBU0 board,
providing a reference to the LED amplitude scan, showing an amount of light
delivered to each of 12 SiPMs from 0 to 250 MIP at maximum. An ASIC analogue
memory cell performance was analyzed in relation with the SiPM signal strength.
We observed a non-uniformity and a pedestal shift in the ASIC readout values in
the high gain mode for the higher signals strength.
