mA Generation
Failure Possible Cause Remedy
Wrong
filament
voltage
observed
Filament current may be
wrong, so mA generated
will be wrong. Incorrect
FIL_B_ PLUS voltage -
filament control fault.
INV_B_PLUS voltage low -
battery charge problem.
Faulty or disconnected
filament voltage sense
resistor. Incorrect filament
selected, changing gain of
voltage sensor.
Filament voltage is monitored by a true rms sensing circuit on the Generator
Driver PCB which sends an analog signal to the X-Ray Controller PCB. This
signal is monitored by software to verify that the filament voltage is in the
expected range for the selected filament and technique, before the shot is
initiated. Filament current is similarly monitored. Faults in the filament voltage
regulator would affect INV_B_SEN or FIL_B_SEN signals. Incorrect filament
selection would be seen through SM_FIL_ACK*, and further mitigation is provided
by monitoring the filament current FIL_CUR in software to see if it is in the
expected range for the voltage applied to the selected filament. Software also
checks the INV_B_SEN and FIL_B_SEN signals to verify correct supply voltages.
No filament
current
(filament
voltage
present)
If the connector is
disconnected or a filament
drive wire is broken, the
filament is not heated and
no X-rays can occur. If the
filament sense circuit is
faulty, there could be
normal filament current. P3
disconnected from Filament
Driver PCB. P1
disconnected from tank
A9J1. Broken connection in
cable to tank. Filament
current sense circuit fault.
If the connector at either end is disconnected, no filament drive reachs the
filament, and in addition, X-ray generation is actively disabled by hardware
operating on the TANK_CHAS line. Therefore, the failure results in a safe
condition, but the system is inoperable. If the filament current is actually present,
but a fault in the filament current sensor results in zero output, generation of kVp
could result in normal mA; therefore, kVp should be applied with caution to verify
that mA is correct. If filament current occurs with one filament only, a broken wire
is likely. Operation could continue with the filament that is working correctly.
10
Service
Periodic Maintenance
Contents
Schematics
Illustrated Parts
Installation
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