Tektronix 7B92 Instruction Manual page 27

Calibration-7B92 Service
Control Settings
Perform the Preliminary Procedure at the beginning of
this section.
NOTE
If the 7892 has been operating satisfactorily and it is
desired to touch up instrument calibration for
improved performance, complete steps 1 (a) and 1 (b),
then proceed to calibration step 2. If the instrument
has known operating problems, perform calibration
steps 1 (a) through 1 (k), and then continue with
calibration step 2.
1. Preliminary Trigger Adjustments (R740, R750,
R940, R950, and R364)
a. Connect the low-frequency sine-wave generator to the
7A19 Input with a 42-inch 50-ohm BNC cable and BNC
T-connector. Connect the output of the T -connector to the
MAIN TRIG IN connector with a 42-inch BNC cable.
b. Set the low-frequency sine-wave generator for a
two-division display at 50 kilohertz. Center the display
vertically. Adjust the 7B92 INTENSITY control to view
both the intensified and non-intensified portion of display.
c. Remove the 7B92 from the plug-in extender and
install the 7B92 directly into the B Horiz compartment.
d. Preset the following control settings:
R364
R750
R940
R950
Fully Counterclockwise
Fully Counterclockwise
Fully Counterclockwise
Fully Counterclockwise
e. Rotate the MAIN TRIGGERING LEVEL control for
a stable display. If a stable display cannot be obtained,
adjust Intensity and Focus control for a well-defined
free-running display and set the LEVEL control to
O.
f. ADJUST -R740, Main Arming TD Bias, fully counter-
clockwise, then adjust clockwise until a stable display is
obtained. Adjust R740 an additional 10 degrees clockwise.
g. Press and release the Delayed Triggering LEVEL
control to DLY'D SWP TRIGGERABLE (knob out).
Rotate the Delayed Triggering LEVEL for a stable intensi-
fied display (do not rotate LEVEL control into HF SYNC
area). Adjust the 7B92 and oscilloscope Intensity controls
as necessary for an optimum intensified display.
4-6
Scans bv Outsource-Options =>
h. ADJUST -R950, Delayed Sweep Start TD Bias,
clockwise until the intensified portion of the sweep
disappears. Adjust R950 an additional 10 degrees clock-
wise.
i. ADJUST -R940, Delayed Arming TD Bias, clockwise
until a stable display of the intensified portion of the sweep
appears. Rotate the Delayed Triggering LEVEL control as
necessary.
j. Press the Delayed Triggering LEVEL control to the
(knob in) RUNS AFTER DL Y TIME position.
k. ADJUST-While rotating the DELAY TIME MUL T
dial, adjust R364, Delay Pickoff TD Bias, clockwise until
the DELAY TIME MUL T dial rotation affects the position
of the intensified portion of the display.
I. Remove the 7B92 from the oscilloscope and install
the 7B92 into the 067-0589-00 Plug-in extender. Install the
7B92 and the Plug-in extender into the B Horiz compart-
ment.
2. Check/Adjust Main Trigger Level Sensitivity
(R730)
a. Set the DELAY TIME MUL T dial to 5.00.
b. CHECK-Rotate the MAIN TRIGGERING LEVEL
control and check that the delaying sweep (non-intensified
portion of the display) can be triggered at any point
along the positive slope of the waveform.
c. ADJUST -R730, Trigger Level Sensitivity, to trigger
the display (start of sweep) at any point along the positive
slope of the waveform.
d. Change the MAIN TRIGGERING SLOPE switch to
(-) and repeat steps band c for the negative slope of the
waveform.
3. Check/Adjust Main Triggering I nternal and
External DC Centering (R647, R602)
a. Set the low-frequency sine-wave generator for a 0.5
division display at 50 kilohertz. Vertically center the
display.
b. Change the MAIN TRIGGERING MODE switch to
NORM and rotate the MAIN TR IGGER ING LEVEL
®