PFC-16 PreAmp Filter Card Modification
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                                               Original Rev.  28-JAN-2009
                                                Current Rev.  28-JAN-2009


This note describes the component changes on the PFC-16 circuit board
that are required to implement the new "narrow Gaussian" filters.

To implement the new filter design, the component values must be
changed in three sections of the PFC-16 card: the PreAmp Buffer
section, the First Stage Filter section, and the Second Stage Filter
section.  A total of about 22 components must be changed in each
channel of the 16 channel PFC-16 card.


Preamp Buffer Section Component Changes
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  1. Remove capacitor C20A and replace it with a zero Ohm jumper.

  2. Parallel capacitor C20B with a 47 uFd 6 Volt Tantalum capacitor.
     The positive  (banded)  terminal of the capacitor faces toward
     the next higher number channel on the card.  This new 47 uFd
     Tantalum capacitor is called C20C on the modified card.



First Stage Filter Section Component Changes
--------------------------------------------

  1. Remove the two 220 nFd capacitors at C30A and C30B and
     replace them with two 10 nFd capacitors.

  2. Remove the 1500 pFd capacitor at C32 and
     replace it with a 820 pFd capacitor.

  3. Remove the two 560 Ohm resistors at R33A and R33B and
     replace them with two 845 Ohm resistors.

  4. Remove the two 1650 Ohm resistors at R34A and R34B and
     replace them with two 2000 Ohm resistors.

  5. Remove the two 220 pFd capacitors at C35A and C35B and
     replace them with two 150 pFd capacitors.



Second Stage Filter Section Component Changes
---------------------------------------------

  1. Remove the two 47 nFd capacitors at C41A and C41B and
     replace them with two 332 Ohm resistors.  On the modified
     card these two resistors are labeled R41A and R41B.

  2. Remove the 432 Ohm resistor at R42 and
     replace it with a 1000 pFd Capacitor.  On the modified
     card this capacitor is labeled C42.

  3. Remove the two 47 nFd capacitors at C43A and C43B and
     replace them with two 845 Ohm resistors.  On the modified
     card these two resistors are labeled R43A and R43B.

  4. Remove the two 10 nFd capacitors at C44A and C44B and
     replace them with two 2000 Ohm resistors.  On the modified
     card these two resistors are labeled R44A and R44B.

  5. Remove the two 2490 Ohm resistors at R45A and R45B and
     replace them with two 100 pFd capacitors.  On the modified
     card these two capacitors are labeled C45A and C45B.

  6. Remove the two 470 nFd capacitors at C46A and C46B and
     replace them with two zero Ohm jumpers.