analyzing LASER and LED/TDC calibration files, we found 2B09-0
with only one PMT working (2B09-00 was without HV).
It was caused by a broken splitter.
Checking into PISA Left/Right warnings e-mails, you can see that
this problem started during run 17548 (04-May-99).
Everything is fine now!
A presto,
Nicola