9600 Service Manual - gmecorp-usa.com

C-Arm Control 25
D/A SECTION
U18 and U31 are quad D/A converters (DAC 8408) which provide analog current
output signals. These four current output channels are labeled as IOUT1A -
IOUT1D. The current outputs from the D/As are converted to a voltage (0-10
VDC) by current to voltage converters U28, U29, and U33.
The analog outputs for U18 and U31 are described below.
D/A U18 Pin Assignments
CHA - Pin 4 - Not Used
CHB - FILCNTRL - Pin 6 - This is a control voltage for the filament B+ circuitry
used to regulate the tube current (mA); see TP10. Refer to mA Generation
Section for more information about this signal.
CHC - CAM_GAIN - Pin 25 - This signal controls the video camera gain; see
TP13. Refer to the Image System section for more information about this
signal.
CHD - Pin 23 - Not Used (CAM_BLK)
D/A U31 pin assignments
CHA - Pin 4 - Not Used (Target)
CHB - Pin 6 - Not Used
CHC - KVCONT - Pin 25 - This is a control voltage for the high voltage circuitry
that is proportional to the desired kV; see TP19. Refer to the kV Generation
section for more information about this signal.
CHD - MACONT - Pin 23 - This is a control voltage for the tube current circuitry
that is proportional to the desired mA; see TP18. Refer to the mA Generation
section for more information about this signal.
Negative 10 Volt Reference
The -10 VDC reference, VR1, provides the necessary voltage reference for the
digital to analog conversion. Its output is buffered by U30A, Q14 and other
related components.
NOTE: Loss of the reference voltage will give a “Regulator Fail” error message on the
Control Panel Display after an exposure has been made.