mA Generation
Failure Possible Cause Remedy
No filament
voltage
observed
Filament voltage at
FIL_VOLT on Generator
Driver PCB is zero. No
FIL_B_PLUS voltage –
Resistors open, cable
problem. No FIL_B_PLUS
- transistor open, capacitor
short. No filament drive
signals present. Faulty or
shorted filament voltage
sense resistors. Failure of
filament voltage sensor at
Generator Drive PCB.
Broken connection to X-Ray
Controller PCB. Failure at
X-Ray Controller PCB.
Filament voltage is monitored by a sensing circuit on the Generator Driver PCB,
and sends an analog signal to the X-Ray Controller PCB. This signal verifies that
the filament voltage is in the expected range for the selected filament and
technique, before the shot is initiated. The fault indicates a drive failure, a supply
failure, a sensor failure or an interconnection failure. The INV_B_SEN line
provides an analog signal to the X-Ray Controller PCB and is monitored by
software. Additionally, the FIL_B_SEN line is monitored by software. If there is
no drive, FIL_DRV_OK* on the Generator Driver PCB is high, as there will be no
filament current sensor output at FIL_CUR on the Generator Driver. Absence of
filament voltage at the tube prevents X-ray generation.
Filament
Voltage Error
If the wrong voltage is
applied to the filament, the
mA will also be wrong.
Filament B plus wrong, duty
ratio of filament drive pulses
wrong, wrong filament
selected, failure of filament
regulation, sensor gain
wrong.
Filament voltage is monitored by an RMS to DC converter on the Generator
Driver PCB, and fed to the Filament Driver PCB. If the wrong voltage occurs at
FIL_VOLT relative to FIL_VOLT_REF, this is observed by the X-Ray Controller
PCB. A fault in the RMS converter or the cable from the Filament Driver PCB
might also result in the wrong voltage at FIL_VOLT, but there is also a filament
current sense circuit, which will confirm the error. If there is an incorrect gain, this
could be caused by the wrong filament relay selection or a problem in the relay
which is on the Filament Driver PCB, but if the wrong filament selection is made,
the SM_FIL_ACK* signal will be in the wrong state. Additionally, the mA is
sensed on the HV Supply Regulator PCB, providing an independent check on the
correctness of the filament drive. Other faults in the Filament Driver PCB such as
wrong FIL_B_PLUS voltage are also monitored by software.
9
Service
Periodic Maintenance
Contents
Schematics
Illustrated Parts
Installation
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