Agilent Technologies 856290216 service manual Intensity Problems

13.Verify that the front-panel intensity adjustment when used with the A17R21 Z FOCUS changes the peak-to-peak voltage at TP9 by 25 V. Access the intensity adjustment by pressing (DISPLAY), IEJmS3TY and turning the front panel knob.

14.Set the front-panel intensity to minimum. Set A17R21 Z FOCUS and A17R26 X FOCUS 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 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 spectrum analyzer, press (m), INTENSITY.

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

3.If the intensity 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, “Adjustment Procedures.” Verify that A17Rll 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 ps apart. If the blanking pulses are not correct, check the BLANKING output of the A2 controller assembly and cable W7.

6.If blanking pulses are present, check A17TPlO with the oscilloscope. The TPlO signal should vary with the front-panel intensity adjustment, and be approximately 40 Vp-p maximum. The signal will be composed of both blanking pulses and varying intensity levels for the lines being drawn.

a.If a proper signal is not present at A17TP10, check A17Q1, Q2, CRl, and CR2.

b.If the TPlO signal does not vary with the front-panel intensity adjustment, check the signals at A17TP4 and A17TPl. Both signals should vary with front panel intensity adjustment. The TP4 signal should be up to 4 Vp-p, and TPl signal should be up to approximately 12 VP-p.

Warning The Al7 CRT driver contains lethal voltages with lethal currents. Use extreme care when servicing this assembly. Always disconnect the power cord from the instrument before servicing this assembly. Failure to follow this precaution can present a shock hazard which may result in personal injury.

13-10 Display/Power Supply Section