Card Cage and PCBs SediGraph III 5120 Service
2-12 Mar 2010
300/17700/011, i386EX CPU PCB
The i386EX CPU card features the i386EX chipset, 128kBytes of NVRAM (Non Volatile
Random Access Memory), DRAM (Dynamic Random Access Memory) of up to 32MB with a
SIMM socket, 16MB of Boot Block Flash with BIOS configuration, Boot selectable PCMCIA
on board Flash, Watchdog timer interfaces with the SediGraph 5120 with a 160 pin DIN
connector. The PCB features the following:
• This PCB controls the action of the SediGraph, generates its own clock and clocking
signals as required for proper operation.
• There is one eight-bit parallel port printer interface at the backplane connector. In the
SediGraph this port is not used.
• The 128kB of NVRAM will have a lifespan of greater than 10 years even with no power
applied.
• There is a buzzer for notification of an error should one occur.
• There is a reset switch on this PCB, which will reset the CPU and the MICBUS when
pressed. The reset switch is normally not accessible.
512/17702/011 I/O & Control PCB
The I/O & Control PCB allows connection of the 5120 to a computer, provides interfacing
connectors for the instrument, and monitors critical functions of the 5120. The PCB features
the following:
• An RS232 connector and a 9-pin connector on the edge of the PCB, addressed as Com2.
• X-ray & Photomultiplier tube interface - the PCB has four independent 1,000,000 count
A/D channels used to monitor X-ray current, X-ray voltage, Photomultiplier voltage
and the temperature. The PCB has a 2MHz clock to run the V/F converters on the PCB,
monitors the Key-switch position, reports this position to software, monitors the
interlock circuitry (Door, key-switch, top panel and the X-ray ON LED condition) This
board latches into X-Ray OFF mode whenever the top panel is removed or when there
is an over current condition of the X-ray tube. Both of these conditions require the
operator to turn the key-switch Off and back On to generate X-rays.
• Period Averager interface - performs the period averaging function for both the Kilo-
counts and the temperature conversions needed for proper operation.
• Fan monitor - there is a fan monitor bit for each fan to determine when the fan’s speed
has fallen below a set threshold. When a fan’s speed gets below approximately 30% of
the rated speed, an error message is generated to alert the operator to the problem.
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