Hologic QDR 4500 - Beam Flattening Problems

Section 6 - Fault Isolation
6-11
Verify upper arm parallelism with respect to lower arm assembly. Referring to Figure
6-2, assure dimension x
1
is equal to x
2
.
System Fails X-Ray Beam Alignment Verification
Align the X-ray beam and recalibrate the aperture. If this fails, inspect the aperture assembly for
any loose hardware or excessive play in the aperture plate. Check the aperture assembly
encoder’s belt tension. If the belt is too tight, it may cause encoder readback errors and cause the
calibration program to fail.
Beam Flattening Problems
System Consistently Fails the Beam Flattening Procedure
1. Check for loose, misaligned, or defective aperture assembly, collimator cup, or pre-
collimator disk. (Refer to X-ray Alignment Problems, above.)
2. If the X-rays are unstable or “dancing”, monitor the X-rays on the SUSQ bar graph
screen for any amplitude shifting of the defective signal display.
3. If shifting is taking place, check/replace the X-ray controller assembly and X-ray
tank connections. Check the X-ray peak potential and tube current waveforms and
monitor for waveform distortion. This may indicate a defective interconnection
cable, X-ray tank, or power supply.
4. Check output signal level. You may have to reset the ADC gain level.
5. Check for bad detectors in the detector array assembly. Load the Field Service Tools
disk and run SQCHECK.
6. Check the filter drum to see that it is installed correctly. Check the segment readback
values in SUSQ with X-rays ON.
7. Check for lead fragments in the X-ray beam. Inspect the collimator cup, disk, and
aperture assembly.
8. If a failure occurs during a whole body or lateral flattening, recheck the AR and TX
motor cal files. The X-rays may be hitting the table edge. Make sure the drives are
operating normally. Examine the beam flattening scans for any unusual indications.
If an error message is displayed, go to the
Error Message List
heading on page 6-19.