6.Turn off the analyzer and place Al7 in the service position. Connect the ground lead of a high-voltage probe (HP 34111A) to the chassis, and use it with a DVM to measure A17J7( 10).

7.The nominal A17J7(10) voltage is -1600 Vdc, but the CRT will function with this voltage within 200 V of -1600 Vdc.

8.Adjusting A17R34 COURSE FOCUS should vary the A17J7(10) voltage by 150 V. If these voltages are correct, suspect the CRT.

9.Check the A6Al High Voltage Module cathode supply output at A17TP16 using a high voltage probe. If the cathode voltage is -2450 V +/-250 V, check the Focus Grid Level Shifter.

10.If the cathode voltage is not correct, check the A6Al High Voltage Module and its connections.

11.Connect an oscilloscope probe to A17TP9. This signal corrects the focus for the X position of the CRT beam, and for intensity level. It also provides the front-panel focus adjusting voltage.

12.Press [m), MORE, and FOCUS. While turning the front-panel knob, verify the dc level of the signal at TP9 adjusts about 30 Vp-p.

13.Verify that the front panel INTEN adjustment plus A17R21 Z FOCUS changes the peak-to-peak voltage at TP9 by 25 V.

14.Set front panel INTEN to minimum and Z FOCUS fully counterclockwise and A17R26 X FOCUS to fully counterclockwise. Verify that the peak-to-peak voltage at TP9 is about 40 Vp-p (due to X-Dynamic Focus circuit).

15.If circuit operation seems correct, A18Vl CRT is probably at fault.

Intensity Problems

Intensity problems, or absence of display, can be due to the Al7 assembly’s Intensity Amplifier (function block A), Intensity Grid Level Shifter (function block B), CRT (A18Vl), interconnections, or lack of proper supplies or inputs to A17.

1.On the HP 8560A press (m), MORE 1 of 2 , INTEN .

2.Rotate the front-panel knob (RPG), and check that the intensity changes from dim, but readable, to bright.

3.If the INTEN function does not function properly, troubleshoot the A2 Controller assembly.

4.Perform the preliminary and Z-axis portions of the Display Adjustment in Chapter 2. Verify that A17RlO CUTOFF functions properly. If A17Rll CUTOFF does not function properly, place the Al7 CRT Driver in the service position.

5.Verify that blanking pulses are present at A17TP2 using an oscilloscope. The pulses should be normal TTL levels, approximately 1 ps wide and 4 or 7 ~LS apart. If the blanking pulses are not correct, check the BLANKING output of the A2 Controller Assembly and cable W7.

Display/Power Supply Section 12-9