Service manual

LUMISCAN ACR-2000 SERVICE MANUAL – SECTION 7.0 DIAGNOSTICS
7.2.5 DI-2000 Self Test Failure
If Autozero and AGC both fail, the PMTs are suspect.
If Autozero fails, there may be too much ambient light in the room.
If AGC fails, perform the PMT Output Voltage Adjustment and Reference Blue LED
Adjustment which is in Chapter 5.
7.2.6 No Photo-Multiplier Tube Output
Verify that the Laser is emitting light, by using DDT.EXE option 20, with the Laser interlock
installed. If the Laser is not emitting light, the Laser Module needs to be replaced.
Attempt to perform the PMT Output Voltage Adjustment which is in Chapter 5. The initial
measurement of the PMT Output Voltage mean data value before the adjustment should normally be
between 600 and 1000. If the mean data value is near 4095, the PMTs are probably not getting
voltage from the PMT High Voltage Power Supply.
CAUTION
THE PMT HIGH VOLTAGE IS SEVERAL HUNDRED VOLTS DIRECT CURRENT
Using a Digital Volt Meter set to DC Volts, check the PMT High Voltage by measuring the voltage
from the top pin of Test Point 2 (voltage) to the bottom pin of Test Point 1 (reference) on the PMT
Preamp PCA which is located behind the front cover. The voltage should be above
–300VDC. If the voltage is near zero, the PMT High Voltage Power Supply is likely to have failed.
If there is voltage at Test Point 2, check the cable between the PMT Preamp PCA and the Data
Acquisition PCA for bent pins.