CMU Instrument Design and Function Description
1100.4903.82 3.7 E-4
Standby converter
and control unit
The third printed circuit board which serves as a connection between
the first and second board accommodates the control and monitoring
circuit parts. Besides, it includes the standby converter, which
generates a +12-V standby voltage from the 380 VDC voltage of the
PFC circuit.
Connection
The POWER SUPPLY is directly connected to the MOTHERBOARD
via a 96-pin FUTURE-bus connector on the MOTHERBOARD and
screwed to the integrated rear panel of the CMU with its casing.
MOTHERBOARD
The MOTHERBOARD consists of five individual printed circuit boards: MOTHERBOARD1,
MOTHERBOARD2, FRONTPANEL BOARD, REARPANEL BOARD1 and REARPANEL BOARD2.
MOTHERBOARD1
The MOTHERBOARD1 is the central motherboard and serves as
connection between most of the modules. It supplies the modules both
with voltages and control, status and bus signals in various layers (12-
layer multilayer).
The MOTHERBOARD1 accommodates various ISA bus driver devices
for the PCMCIA INTERFACE control as well as protective circuits.
These protective circuits consist of diodes and polyswitches (current-
dependent, self-opening and closing fuses) and protect against
external overvoltages of the interface signals.
Nine LEDs indicate the status of the supply voltages and help with
troubleshooting.
On MOTHERBOARD1, a circuit for temperature-dependent instrument
fan control is also implemented:
The individual module temperatures are polled by the FRONT
MODULE CONTROLLER of the CMU. This information is passed on
via the DIGITAL BOARD to the fan control with the aid of a control
signal. The instrument fan is controlled such that an optimum module
temperature is achieved on the one hand and as little noise as possible
is emitted by the fan on the other hand.
MOTHERBOARD2
The MOTHERBOARD2 serves for supply and connection of the
modules located higher at the side, the REFERENCE BOARD and a
further option.
For connection with MOTHERBOARD1 two 50-pin ribbon cables are
used.
FRONTPANEL BOARD
The FRONTPANEL BOARD is located at the front of the instrument
frame and accommodates the external interfaces DATA1, DATA2,
AUX3 and SPEECH. Besides, the six LEDs for the display of the active
RF inputs/outputs are located there.
For connection with MOTHERBOARD1 a 50-pin ribbon cable is used.
REARPANEL BOARD1
The REARPANEL BOARD1 is screwed to the integrated rear panel of
the CMU below the POWER SUPPLY and accommodates the external
interfaces IEEE, LPT, COM1, COM2, monitor and keyboard.
For connection with MOTHERBOARD1 two 34-pin ribbon cables are
used.
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