GE Medical Systems PRODIGY Service Manual page 110

Problems at the head end of the scanner can be caused by a limit switch
being out of position (thus the arm runs into the frame before the Limit Switch)
or because the High Voltage Cables are tied down incorrectly where they
snake around from the Rear Longitudinal Carriage to the panel under the
Tube Head (High Voltage Cable Trough). If the cables are tied down too far
toward the head end (at the point where the three tie downs are), they can run
into the Longitudinal Motor Assembly and hold the arm away from the head
end Limit Switch.
A slip clutch is part of the longitudinal motion system to limit torque. This is a
feature to protect the patient should he/she pinch an arm or leg between the
back side of the scanner and the Arm Column. If the Slip Clutch is set too
loose, it will fail to move the belt and will just "slip" as the motor turns. This
may produce the following symptoms:
Check all appropriate gears and pulleys. Verify that the set screws are
tightened and the gears and pulleys are not out of position.
If the longitudinal motion seems to be acceptable, but the number of steps in
the Quality Assurance Test is failing, check the position of the Limit Switches.
On Total Body scans, a limit switch out of position could allow the Source/
Detector Carriages to hit the frame or panels of the scanner before the Limit
Switch.
If the mechanical stop is reached before the Limit Switch is actuated, check
carefully to see which part of the Arm Assembly is in contact with the Table
Assembly. The front part of the Lower Transverse Extrusion is clamped to the
Longitudinal Drive Cable at the front of the scanner. If the Lower Transverse
Extrusion is not clamped in such a way that it forms a 90 degree angle with
the length of the table, the rollers at the front end of the Lower Transverse
Extrusion may strike the end of the scan table before the Limit Switch is
actuated.
Check the motor for a broken wire in one of the internal coils, or a bad
electrical connection to the Centent Motor Controller.
4-124Troubleshooting
• Slip Clutch
• failure of Quality Assurance scan Mechanics test
• compressed image in limited areas of the image
• a Longitudinal Mechanics diagnostic failure
• Gear and Pulley Positioning
• Limit Switch Positioning
• Longitudinal Motor
• Longitudinal Centent
DPX-NT Service Manual (Rev A- 1999)