Longitudinal Motion Failure; Limit Switch Tripped During A Scan - GE Medical Systems PRODIGY Service Manual

4.2

Longitudinal Motion failure

4.2.1 Limit Switch Tripped During a Scan

4-122Troubleshooting
Solution 1: The pulses that normally enter the cSBC board at J14 (the
black wire at the center of the connector) may have stopped. These
pulses are necessary to keep the cSBC from resetting. These pulses can
be seen on a cSBC board LED.
Use the DPX-NT service software (Tools/Diagnostics/Scanner Motion /
Motion Commands Tab) to set the joystick speed to 50 steps, enable the
joystick and watch the LED. If the OMI is working the LIght will flash
when the Transverse Motor is run. If the LED flashes when the
mechanics are engaged, but the error still occurs, the interrupt was
invalid. Check for arcing in the high voltage system or replace the cSBC.
If the LED D9 (B in figure 4-1) does not flash,
• Verify that the slotted disk at the front of the lower arm rail is in the
middle of the slot between the photo diode and photo transistor.
• The slotted disk must be completely flat and remain in the center of
the sensor slot during its entire rotation.
• If the slotted disk has been in physical contact with the optical sensor,
the sensor may have debris on it, disassemble this mechanism, and
clean the sensor and the slots of the disk.
• Check the Cable running from the cSBC to the OMI for a cable break
by checking the individual wires for continuity.
• cSBC/ OMI fail to see longitudinal motion during a patient scan, an
interrupt signal is generated by the cSBC which resets and closes the
shutter.
• A slotted disk at the foot end of the table on the pulley for the
Longitudinal Drive Belt rotates through an infrared beam (OMI), and
pulses are sent to the cboard when there is transverse motion.
• The transverse and longitudinal motion detection system (on FOINK) is
operational during patient scans and the find block portion of the daily
QA. If the problem occurs during a quality assurance, for instance, it may
be the high voltage system is arcing or the OMI may be malfunctioning.
DPX-NT Service Manual (Rev A- 1999)