Service manual

LUMISCAN ACR-2000 READER SERVICE MANUAL - SECTION 5.0 SERVICE ADJUSTMENTS
5-11
5.4.4 PMT Output Voltage Balancing
1. Place a well erased 14 x 17” image plate into a cassette. Expose with a dose of 4 mAs at 85 kVp, 71”
SID. If a 1mm thick copper plate is available, position the copper plate over the x-ray emitter. This will
provide a more uniform exposure. Verify with a high resolution x-ray dose meter that the dosage is
4 mR +/- 0.05 mR. Be sure the shutters are opened sufficiently to provide full exposure to the entire
image plate. Expose the image plate with nothing on top of it.
2. Turn the ACR-2000 Reader off.
3. Remove the front and rear enclosures. Install the cheater keys for Laser power.
4. Remove the top cover of each PMT tower.
5. Minimize ambient light as much as possible and cover the system well with a dark cloth.
6. Apply power to the ACR-2000 Reader.
7. Remove the exposed plate from the cassette and place into the feed slot.
8. Connect oscilloscope trigger sync. channel to the top pin of TP8 (“SOS”) on the DACQ PCA.
Trigger on –Slope and set sweep to 1 ms/div. Connect channel 1 to the top pin of TP9 on the DACQ
PCA.
9. Navigate to the “tools” directory. Run DDT. Select option 16.
10. Choose option 20. Observe data scrolling up the screen.
11. Press “m” to start the transport motor. When prompted enter 1956 to set the motor speed.
12. Observe the two peaks in the waveform. The left peak is the left PMT as you are facing the Reader.
The right peak is the right PMT. Find the PMT with the lowest amplitude.
13. Using the potentiometer on top of the PMT, adjust the lower amplitude PMT to match the amplitude
of the other PMT. If the lower gain tube cannot match the amplitude of the higher PMT, both PMT’s
must be replaced as a set.
14. Turn the ACR-2000 Reader off.
15. Remove the Laser cheater keys.
16. Replace the PMT tower covers.
17. Replace the front and rear enclosures.