LORAD AFFINITY Series, Service Manual

Page: 67 / 214

P/N 9-500-0255 4-11
Service Manual
Chapter 4: Calibrations and Performance Checks
Exposure System Calibration
19. Select intermediate kV levels and make an exposure at each setting. Confirm that the
voltage readings on the meter are within 2% of the kV setting. If they are not, make small
adjustments at 20 kV and 39 kV to “dial” in the intermediate kV levels while maintaining
the ±2% at all kV’s.
20. For initial setup and calibration, skip this step. If all service procedures have been com-
pleted, return the unit to the user mode (S2 switch 1 = OFF), and replace all previously
removed covers and panels.
4.2 Check mA Calibration
Check the mA calibration as follows:
1. Turn the unit off. 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.
2. On the HV Multiplier, connect a Digital Multi Meter (set to current) to the mA Current
Jack (Figure 4-3, Item 13).
3. Take an exposure at 30 kV, manual mode, 100 mAs. The meter should read 100 mA. If
not, adjust R2 on the HV Control/Filament Board.
4. Repeat Step 2 till the meter reads 100 mA.
4.3 Filament Current (mA) Calibration
This procedure sets the filament current to produce the desired mA at each kV station for the
large and small focal spots in the Affinity. This procedure also calibrates the reduced mA at
each kV station for large focal spot using an HTC Bucky.
Adaptive Filament —This function allows you to make small adjustments to the filament DAC
value when necessary each time an exposure is made. Turning switch # 5 (S2) ON enables
the function. This function is designed to keep the starting mA correct, as parameters vary
over time. It is recommended that this function is enabled.
Note… This feature is automatically disabled when Filament Current Calibration
(AUTO CAL) is ON.
Note… This calibration must be performed using Manual Exposure mode only.
1. Turn the unit OFF.
2. Remove the Gantry’s right side panel (to access the Host Microprocessor board) as per
Chapter 6, Section 2.1.1.
3. Remove the Patient Handles and the C-arm top cover to access the Filament Protection
Board as per Chapter 6, Section 3.1.2.
4. On the Microprocessor Board, set the unit for the service mode (S2 switch 1 = ON).