5-6 P/N 9-500-0255
Service Manual
Chapter 5: Maintenance—General
Troubleshooting
Magnification device) to indicated compression force and compression thickness,
respectively. The display of both force and thickness is located on the compression
mechanism. The force and thickness is transmitted via the printer or flasher port for
permanent record.
Rotation Mechanism
The rotation mechanism permits the C-arm to be rotated between +195° and -150°.
A fail-safe elector-magnetic lock is used to maintain mechanism lock in the event of
power failure. Release of the lock is by activation of switches located on the C-arm
and is electrically controlled by the Power Control PCB.
There is a potentiometer associated with this motion to provide input for display of
the rotation angle, and to transmit this information to the printer and flasher port for
permanent record.
Vertical Travel Assembly
The vertical travel assembly (VTA) is used to move the C-arm up and down. The
motion is motor driven by an AC actuator, which is activated by switches located on
the C-arm or foot-switches, and is electrically controlled by the Power Control PCB.
There is a strain gauge located at the base of the actuator to sense the upward force
applied externally to the C-arm assembly. This strain gauge signal is processed by
the C-arm Safety PCB and inhibits downward motion upon the sensing of
approximately 154 N (35 lb).
3.1.7 Exposure Control
The exposure function is controlled by the Host microprocessor. Several inputs are
monitored and must be correct before an exposure may be initiated. These include a
valid combination of image receptor and aperture, a rotor ready signal, and
continuous activation of the X-ray switch(es). The X-ray switch(es) must be released
prior to the initiation of subsequent exposures. There are four exposure modes
available:
• Manual
• Auto-Time
• Auto-kV
• Auto-Filter
Manual
This mode provides the selection of kV, mAs, and Filter.
Auto-Time
When this mode is selected, the kV, Filter, and density are the only factors that are
selectable. The exposure is terminated at a value of mAs that is determined by the
AEC algorithm to yield an optical density to which the system has been calibrated. A
post-mAs readout indicates the actual mAs value at the termination of the exposure
and remains displayed until the initiation of the next exposure. This mode is valid for
use with either the Molybdenum or Rhodium filter selected. The exposure mAs may
be modified up to ± 80% by incrementing or decrementing the DENSITY function. If
determination is made during the AEC sample period (first 50ms) that the exposure
will exceed the "Back-Up-Time", the exposure is terminated.
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