[Nakashima, Enomoto, Michimura]

We modified the hacked DC QPD amplifiers for baffle PDs to use them for temporary amplifier for OMC DC QPD.
Related klogs: #3958, #4008, #6682, #8044

What we did:
 1. Checked the OMC DC QPDs as reported in klog #8044.
 2. Took the hacked DC QPD amplifier (S1707229) from EX0.
 3. Modified S1707229 and S1504142 so that they can be used for OMC DC QPD (see attached photo).
 4. Installed Universal Whitening Filter with DC Power to OMC rack.
 4. Did the cabling for OMC DC QPD: feedthrough -> the modified hacked DC QPD amplifier -> universal whitening chassis with DC power -> AA filter -> ADC (see, also klog #6682).

Modifications for the DC QPD amplifiers:
 - As shown in JGW-D1809207, anode A1,A2,A3,A4, and cathode of the OMC DC QPD is connected to pins 2,7,3,8, and 4 of Dsub 9 pin connector at the vacuum feedthrough, respectively.
 - Dsub 9pin male connector with a set of cables attached to the hacked DC QPD amlifier was replaced with Dsub 9pin female connector, and pin assignments for the cables are modified.

OMC DC QPD    DB9     DC QPD amplifier
A1         -> pin2 -> amplifier circuit for anode a
A2         -> pin7 -> amplifier circuit for anode b
A3         -> pin3 -> amplifier circuit for anode c
A4         -> pin8 -> amplifier circuit for anode d
cathode    -> pin4 -> reverse bias of +3V