Modifications to Rev 2 DOM Main Board
PMT signal front-end circuits


Component Changes

Circled components on the schematic are to be changed. 

Consult the  Top Side Image    for top layer changes.
Consult the  Bottom Side Image    for lower layer changes.

Changes for U44 and U48 stages, the input to ATWD Channel 0:

  1. Replace U44 with OPA689A (Burr Brown/TI)
  2. Replace R52 with 100Ω
  3. Replace R53 with 100Ω
  4. Replace R59 with 215Ω
  5. Replace R60 with 1.5KΩ  (bottom of board)
  6. Replace R62 with 2.66KΩ
  7. Replace R61 with 3KΩ   (bottom of board)
U44 has more abrupt limiting characteristics, at the expense of higher power resumption.  These changes recover acceptable amplifier behavior and limiting for the duration of testing with DOM MB Rev 2.  Rev 3 implements significantly different topology.

Disable U41, and ATWD Channel 1

  1. Rotate R273 on the pin nearest U42,  so as to point the other end toward C341.  Solder a jumber from the nearest end of C341 to the 'floating' end of R273
The jumpering of the input of U42 to Vref (i.e. Pedestal voltage) removes the possibility that the overdriving of U41 will cause baseline shifting in the ATWD.

Changes for U53  stage, the input to ATWD Channel 2:

  1. Install resistor R? 100 ohms to the non-inverting input of U53.
  2. Replace R30 with 30.9
  3. Replace R54 with 63.4
  4. Replace R34 with 2K
  5. Replace R31 with 2K
  6. Replace R101 with 20
These changes improve the performance of ATWD channel 2, greatly reducing the ringing of the circuit.

Pulser Changes, Ringing reduction

  1. Remove R185 (1 Ω)  (Location)
  2. Place 1 Ω  on footprint JU40
This change improves control of the tendency of  transformer T8 to ring.  The magnitude of the ringing is reduced by about a factor of 10.

Fast ADC Input Change

  1. Replace R74 with a Jumper.
Remove redundant component.

If there are any questions regarding these modifications, contact Gerald Przybylski, LBNL, 510 486 7165  or email _