Chapter 12 637
Display/Power Supply Section
Intensity Problems
7. Carefully measure the grid voltage at A17J7 pin 6, and the cathode
voltage at A17J7 pin 4. The display will work with a cathode voltage
of −2450 V ±250 V, provided the grid voltage (A17J7 pin 6) is 30 to
100 V more negative than the cathode. A17R11, CUTOFF, should be
able to adjust the voltage difference over a 60 V range to account for
tube variations, and achieve proper intensity.
8. If the grid and cathode voltages are correct, turn off the HP 8560E
spectrum analyzer and check A17CR10 with an ohmmeter. If
A17CR10 is good, suspect the A18V1 CRT.
9. If the grid and cathode voltages are too low, turn off the power and
disconnect W8 from the base of A18V1 CRT, and recheck the grid
and cathode voltages.
10.If the grid and cathode voltages are still too low, refer to "CRT
Supply" in this chapter and the "High-Voltage Power Supply
Adjustment" procedure in Chapter 2.
11.If voltages are correct when the tube is disconnected, the CRT is
probably defective.
CAUTION The pins on the A18V1 CRT bend easily. Be careful not to bend pins
when connecting W8 to A18V1.
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