BNC 6040 - Manual (Page 56)

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SECTION 4
MAINTENANCE AND CALIBRATION
CALIBRATION
General
It is recommended that calibration of the 6040 mainframe be verified every 12 months. The instrument
should be allowed to warm up for 30 minutes before beginning the calibration procedure.
Equipment Required
•
HP Model 5370 Time Interval Counter (referred to in the text as TIC) or equivalent.
•
Tektronix Model 485 Oscilloscope (1 ns rise time) or equivalent.
•
Low capacity, high bandwidth probe (Tektronix Model 6160A).
•
Two high quality 50-ohm coaxial cables approximately 3 feet to 4 feet in length and terminated
in BNC connectors on each end.
•
3-1/2 digit (or better) DVM.
•
Variable dc voltage source capable of ±3 V into 50 ohms.
PROCEDURE
NOTE: This calibration should be carried out in the order presented.
Power Supply
The first step in calibrating the instrument is to check each of the power supply voltages to insure
correct setting and minimal ripple. Set the +5 V and -5.2 V supplied to within 0.05 V and the ±12 V
supplied to within 0.1 V. The 120 Hz ripple should not exceed 5 mV p-p. There are test points and
adjustment potentiometers on the power supply board and each one is labeled with the appropriate
voltage. The test points are located in front of the fan.
LCD Contrast
If no characters appear on the LCD display or the contrast is poor, adjust potentiometer R5 on the
Microprocessor board (PCB 6040-3). R5 is located near die key switch, under the ribbon cable for the
LED annunciator board.