HP 8560A, Service Manual

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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
10).
7. The nominal voltage is -1600 Vdc, but the CRT will function with this voltage
within 200 V of -1600 Vdc.
8. Adjusting COURSE FOCUS should vary the voltage by 150 V. If
these voltages are correct, suspect the CRT.
9. Check the High Voltage Module cathode supply output at 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 High Voltage Module and its
connections.
11. Connect an oscilloscope probe to 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 MORE, and FOCUS. While turning the front-panel knob, verify the dc level
of the signal at adjusts about 30 Vp-p.
13. Verify that the front panel adjustment plus Z FOCUS changes the
peak-to-peak voltage at by 25 V.
14. Set front panel to minimum and Z FOCUS fully counterclockwise and X
FOCUS to fully counterclockwise. Verify that the peak-to-peak voltage at is about
40 Vp-p (due to X-Dynamic Focus circuit).
15. If circuit operation seems correct, 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
interconnections, or lack of proper supplies or inputs to A17.
1. On the HP 8560A press MORE 1 of 2 , .
2. Rotate the front-panel knob (RPG), and check that the intensity changes from dim, but
readable, to bright.
3. If the 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 CUTOFF functions properly. If CUTOFF does not function
properly, place the Al7 CRT Driver in the service position.
5. Verify that blanking pulses are present at using an oscilloscope. The pulses
should be normal TTL levels, approximately 1 wide and 4 or 7 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