Because of all the changes in the preamp circuit and the power requirements, there was a need to re-design and replace the preamp motherboards.  Each one supports 48 preamps and connects into the backplane of a preamp box, which houses 96 motherboards.

The new motherboard is and 8-layer printed circuit board with power planes separating planes containing signal traces to minimize noise and cross-talk.  High frequency filter capacitors are placed at both ends of the motherboard.

The preamps are mounted vertically into sockets which are surface mounted.   In the upgrade version, the preamp has two rows of pins that are no longer needed.   Two of these must be pulled in order to ensure that the preamp will be inserted into the socket correctly.  Then the holes will be plugged.

Testing

We are designing two test jigs for the motherboard to be used by the manufacturer to categorize them as "good" or "bad".  The first test jig will be used to measure the capacitance of the 8 pulse injection traces on the bare motherboard.  This will enable us to isolate those boards that may cause problems with pulser calibration.

The second test jig will be used after all components are attached.  It will have two functions 1) to test the circuitry on the 3 power lines and test the functionality of the two power decoupling capacitors and the reverse polarity protection diode 2) to check the placement and values of the calibration pulse injection resistors for all 48 channels.

These testers were designed so that the operation would be reasonably convenient and foolproof while performing this rigorous test in under a minute.

Motherboard Maps of Preamps   Box Maps Central Calorimeter(CC)   Box Maps End Calorimeter   All Box Maps   Motherboard Schematics