Failure Of The 28V Power Supply - GE Medical Systems PRODIGY Service Manual

4.3

Failure of the 28V power supply

The 28 VDC power supply is only enabled when the X-ray tube is ramped,
use the service software (Tools/Diagnostics/ Scanner X-ray) to attempt to
ramp the Tube Head.
When the Supply is ramping the Red and Green LED's on the MAX board will
light.
If the LED's illuminate and the go out:
If the LED's fail to light:
4-126Troubleshooting
• Verify that the slotted disk at the foot end of the scan table 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 FOINK to the OMI for a cable
break by checking the individual wires for continuity.
• Measure the output of the 28VDC power supply, and verify that it remains
constant during the voltage ramping and scanning operations.
• Check the High voltage power supplies, insure they are not arcing (Error
Log - see section 3.2) and are ramping.
• This supply is turned on by the X-ray Relay, so verify that the Relay is
closing. If not, then either the Relay is bad or it is not receiving the signal
from the SBC via the FOINK.
• Check the continuity of the cathode, the filament may have broken, MAX
board TP 4, TP 5 and TP 13 should be continuous with the Tube Head
control cable connected.
• The Tube Head Thermostat is wired in series with the Relay, so if it has
opened, the Relay will not be able to close.
• The 28VDC should also be measured at the Terminal Block. If not, check
the continuity of the wiring and refasten all connections. Also, check the
wire tie-downs for excess tension they may be putting on the wires.
• It may be necessary to check the wiring from the Terminal Block to the
MAX board and to the High Voltage Power Supplies.
DPX-NT Service Manual (Rev A- 1999)