P/N 9-500-0255 4-9
Service Manual
Chapter 4: Calibrations and Performance Checks
Exposure System Calibration
4.0 Exposure System Calibration
This section details the procedures required to calibrate the exposure-generating system.
4.1 Tube Voltage Calibration
This procedure sets the HV Generator Assembly so that the actual kV produced matches the
kV selected/indicated. This check requires use of a high-voltage divider (10,000:1 or
1,000:1), a digital voltmeter, and an adapter cable to connect the voltage divider to the test
receptacle on the unit’s HV Generator Assembly. Refer to Figure 4-3 throughout the
following procedures.
1. Turn the unit OFF.
2. Remove the left and right side Gantry doors (refer to Chapter 6, Section 2.1.1).
3. Locate the Microprocessor Board on the right side of the Gantry and set the unit for the
Service Mode (S2 switch 1 = ON).
4. Locate the HV Generator Assembly on the left side of the Gantry. Wait approximately 6
minutes before proceeding (see WARNING below).
WARNING! To reduce the risk of hazardous electrical shock, do not
attempt service until the LEDs D2 (Inverter Rail) and D35
(Brake Rail) on the HV Inverter Board are extinguished (this
will take approximately 5 minutes). Once the LEDs are
extinguished, do not proceed until an additional 1 minute has
elapsed.
5. Using a coaxial cable (Item 1) and a BNC to banana plug splitter (Item 4), connect a Dig-
ital Multi Meter (DMM, Item 2) to the anode terminal (Item 3) of the HV divider (Item 6).
Position the meter where it can be read from behind the protective radiation shield.
6. Connect the HV divider’s ground wire (Item 8) to an unpainted metal surface on Gantry.
7. Connect one end of the HV Adapter cable (Item 10) into the voltage divider receptacle
(Item 11), and the opposite end into the HV test well (Item 12) on the HV Generator
Assembly.
8. Turn power ON to unit.
Note… Skip Step 9 when performing the Tube Voltage Calibration as part of the
initial installation procedures.
9. Perform the kV Control Offset Calibration Procedures, Section 9.1
10. From the Run Mode, set the unit for a Manual mode exposure at 30 kV, 150 mAs. Moni-
tor the voltmeter from behind the radiation shield (if equipped), then conduct the expo-
sure.
11. The voltage reading on the voltmeter for 30 kV should be 3.0 VDC (±0.06 VDC using
10,000:1 voltage divider), or 30 VDC (±0.6 VDC using 1,000:1 voltage divider).
12. If the voltage reading is not within the specification above, adjust R41 on the HV Control
Filament Board (part of HV Generator Assembly). Turn R41 clockwise to increase kV, or
counter-clockwise to decrease kV (two turns equals approximately 1 kV).
13. Repeat Steps 9, 10, and 11 until the voltage reading at 30 kV is +
2% of the VDC speci-
fied in Step 11.
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