GE Alpha RT 32551, Installation Instructions Manual

Page: 80 / 99

5 Setups, alignments and adjustments
74 GE Healthcare 32551-IMG rev 6
5.2.10 Light field intensity adjustment
The light intensity is adjusted at the factory. If adjustment according to
local regulations is necessary, follow the instructions below.
NOTE!
The unit has been adjusted at the factory with 60 Hz main voltage
frequency. If the unit is being installed to 50 Hz mains network, adjust
collimator lamp voltage at 11 V. Adjust and check the light intensity as
described below.
For proper adjustment a lux-meter is recommended.
The collimator lamp intensity is adjusted by R12 and measured at
reference voltage test point TP 8 - TP 9 on the Supply Board.
Measure light intensity at each corner of the cassette holder. Minimum
average of these values should be the amount of LUX (ISLC’s) that local
regulations require. Take note of the effect of the examination room
lighting unless it can be totally switched off.
The halogen lamp lifetime increases when lamp voltage is decreased and
vice versa.
Fig 5.9. Supply board
5.2.11 X-ray field alignment
1 Go into the service mode by pressing the kV- and density- buttons
simultaneously and holding them until “ser” is displayed on the timer
display.
2 Select the manual mode with 25 kV and 20 mAs.
3 Place a loaded cassette on the cassette holder so that the cassette
overhangs 20 mm on the chest wall edge of the holder.
4 Mark the chest wall edge of the film with a ruler placed 20 mm back
from the chest wall edge of the film. (The ruler now shows the actual
chest wall edge).
5 Make an exposure and develop the film. The exposed area between
the ruler and the chest wall edge of the film must be less than 6 mm
and more than 1 mm in USA, less than 3 mm and more than 0 mm in
Europe.