Tektronix 7B92A Maintenance Manual page 78

h. Connect the digital voltmeter between TP345
and chassis ground.
B9. Adjust Delayed Triggering Arming Tunnel Diode
Bias
a. Adjust-Arming
counterclockwise until Delayed sweep starts again.
Record the voltage
counterclockwise rotation of R345 until Delayed sweep
again disappears. Record the voltage at TP345.
b. Adjust-Arming TD Bias, R345, for the average
of the two voltage readings recorded in part a of this
step. Delayed sweep should be visible.
B10. Adjust Delayed Triggering Gate Tunnel
Diode Bias
a. Disconnect the digital voltmeter from TP345
and connect it to TP355; record the voltage.
b. Adjust-Gate Bias, R355, counterclockwise until
Delayed sweep disappears.
TP355.
c. Adjust-Gate Bias, R355, for the average of the
two voltage readings recorded in parts a and b of this
step.
B11. Adjust Delayed Triggering Internal DC
Balance
a. Set Delayed Triggering LEVEL control to "0".
b. Adjust-Int DC Bal, R245, for a Delayed sweep
trigger point at graticule centerline. See Fig. 5-9 for
reference.
B12. Adjust Delayed Triggering Sensitivity
a. Adjust-Trig Sens, R325, for a Delayed sweep
trigger point at approximately 0.5 division from bottom of
waveform as Delayed Triggering LEVEL control is
rotated through negative (-) portion of its range. See Fig.
5-10 for reference.
Setting trigger sensitivity so display is triggered at less
than 0. 1 division should be avoided to prevent erratic
triggering.
@
TD Bias,
at TP345. Continue
Record the voltage at
NOTE
B13.
Balance
a.
b.
R345, trigger point at graticule centerline. See Fig. 5-9 for
reference.
B14.
a.
b.
volts/division switch to 1 V.
c.
an eight-division display at 50 kHz. Center the display
vertically on the graticule. (Lower the Delaying sweep
intensity control.)
d.
intensified zone may be selected for the sweep starting
point as the Delayed Triggering LEVEL control is rotated
throughout its range, and that triggering occurs at least
3.5 divisions above and below the center horizontal
graticule line. See Fig. 5-12 for reference.
e.
and repeat part d for the negative slope of the waveform.
f.
EXT and repeat part d of this step.
g.
and repeat part d for the positive slope of the waveform.
B15.
a.
TRIG IN connector and reconnect it to the MAIN TRIG IN
connector.
b.
MAIN TRIGGERING
Delayed Triggering
Delayed Triggering
5-28
Performance Check/Calibration-7B92A
Adjust Delayed Triggering External DC
Set Delayed Triggering SOURCE to EXT.
Adjust-Ext DC Bal, R225, for a Delayed sweep
Check Delayed Triggering Level Range
Set the Delayed Triggering SOURCE to INT.
Set the vertical amplifier
Set the low-frequency sine-wave generator for
Check-that all levels of the positive slope of the
Check-set the Delayed Triggering SLOPEto-
Check-set the Delayed Triggering SOURCEto
Check-set the Delayed Triggering SLOPE to +
Check Low-Frequency Triggering
Disconnect the 50-Ω cable from the DLY'D
Set the 7B92A controls as follows:
COUPLING
SLOPE
COUPLING
plug-in unit
AC
+
AC