LORAD AFFINITY Series, Service Manual

Page: 68 / 214

4-12 P/N 9-500-0255
Service Manual
Chapter 4: Calibrations and Performance Checks
Exposure System Calibration
5. On the Filament Protection
Board, connect a storage oscil-
loscope to TP2 (mA SENSE)
and TP3 (GND).
6. Turn the unit ON.
7. Install a Bucky on the IRSD.
8. After the Run Mode screen dis-
plays, highlight the Filter data
field, and select the Mo filter .
9. From the Run Mode screen,
access Calibration Screen #1
by pressing
Reset + Right
Arrow four times.
10. Highlight the Auto Cal data
field, then press a Change key
until the field reads: ON.
11. Highlight and change the
appropriate data fields to set
the unit for a Manual mode
exposure at 20 kV, 40 mAs,
Large focus.
12. Make an exposure. The system
will automatically adjust the
starting filament values. Wait
40 seconds, take a second
exposure. Wait 40 seconds,
take a third exposure. After
each exposure, check the
waveform on the oscilloscope
for under- or overshoot (Figure
4-4). Verify that the waveform
appears stable and is at the cor-
rect amplitude for the set kV as
shown in Table 4-3).
Notes… To fully calibrate the system, 3 exposures (at 40 second intervals between
shots) must be taken.
Note the mA Target (“T”) value and the mA Start ( “ST”) value displayed at
the bottom of the screen. The difference between the start value and the
target value should be less than 10.
Figure 4-4: Example—Filament Waveforms Pattern