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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