Log entry time 02:09:28 on November 9,2009

Entry number 298488

Followups:

• 298489 11/09/09 02:15 Kai quick access for fixing ps5~8 missing problem (set offset as 0)

Ramesh and I went for a quick access to fix the missing of preshower (ps) group 
5~8 problem. We first went to the back rack to check the 740 analog sum for 
group5~8 ps. We found there indeed has output signal there. However, we found 
the offset is -15mv, and do a quick run to check the signal, the fTDC of them 
is back at least.  but here are two questions:

1. The offset is -15mv so that it will actually make the ps signal easier to 
pass the discriminator threshold. As the missing signal is back and MCC is 
ready to send the beam, so we just left the hall. If this problem happened 
again, we need to do further check.
2. Ramesh and I clear the offset of 740 to be all zero just yesterday, and it 
went to -15mv just in one day. We are thinking if it is necessary to replace 
all 740 by lecroy 428F of which the offset is stable zero there for several 
days.