GE Senographe DS Manual page 1675

GE Healthcare
Revision 1
a. Access the Senographe installation menu to read the heater parameters with the LF/MO combi-
nation (select SETUP/GENE/INSTAL/GENE/GENE/TUBE/HEATER/LF/MO/Param/I-Value).
b. Explore the 28 kV/A combinations; note the kV values showing a current value equal to 5.600 A.
c. Repeat steps a and b for the LF/RH combination (there is a very low probability of current limita-
tion occurring in small focus).
d. Return to Application Mode (press SETUP).
e. Set the Senographe for 2-point exposure technique at 60 mAs. Make an exposure for each kV
point detected at 5.600 A (LF/MO and LF/RH). Allow at least 60 seconds between each exposure.
f. Repeat steps a and b: If no more kV points are set to 5.600 A, the problem has been resolved. If
one or more points still show a current value of 5.600 A, repeat Calibration Job Card Heater Cur-
rent Scale Factor, then restart this procedure from step a above. If the problem recurs, replace
the X-ray tube.
Note:
If the automatic calibration fails and you recieve arching errors for the LF/Mo calibration point, cal-
ibration can be done manually. Refer to
6-3 Check results
1. Be sure that the Gantry presence parameters PRS_B, PRS_DS, and PRS_IDC are set to yes before
.
proceeding
2. Refer to Job Card CHK A013 - Check mA and mAs
Perform sections
6-4 Completion
If you are handing the machine back to the user at this point, switch the Senographe off, then on again.
7 TROUBLE SHOOTING
You may obtain the message arcing for the last LF/Mo calibration point. In most cases, the tube does not
actually arc. The main cause of the problem is the high mA value seen by the Generator as an electrical
arc in the tube.
On some tubes with very good cold-to-hot emission (usually seen on mature tubes), the reason for this
high mA value is the excessively high filament heating starting current I HEATER set as default in the
software.
This problem can appear when calibrating the Large Focal/Mo Track. The LF/Mo combination requires
the highest mA for the tube (up to 100 mA for 30 kV).
For some kV values (see Table 1 on page 1677), the filament starting value I HEATER is set too high,
leading to mA overshoot.
In fact, when performing this Job Card, the real filament starting value I HEATER required by the tube in
normal operation is lower than the default value.
Note:
The default values cannot be changed except with a new software version. It is therefore neces-
sary to update the filament starting value I HEATER manually for each kV station in Application
Mode.
In Application Mode, the I HEATER parameters are continually updated after each e posure great-
er than 500 ms, and with an I HEATER value limited to +/–2% of the previous value.
If the message arcing is displayed for the combination LF/Mo, proceed with the following solution:
JC-CAL-A-012.fm
6-1 Preparation on page 1756
Service Information and Procedures Class A 2385072-16-8EN
Job Card CAL A012 - X-Ray Tube Heater Current
Trouble Shooting on page
settings.
and 6-3 Check mA calibration on page
Page no. 1675
Senographe DS
1675.
1757.
Chapter 9