Dc Balance. (Circle Denotes Correct Trigger Point.) - Tektronix 7B92A Maintenance Manual

h. Adjust-Gate TD Bias, R155, counterclockwise
until a stable display occurs, then clockwise until display
is unstable.
i. Connect the digital voltmeter between TP145
and chassis ground.
B2. Adjust Main Triggering Arming Tunnel Diode
Bias
a. Adjust-Arming
counterclockwise until a stable display just occurs.
Record the voltage at TP145; continue counterclockwise
adjustment of R145 until TRIG'D light just goes out.
Record the voltage at TP1 45.
b. Adjust-Arming TD Bias, R145, for the average
of the two recorded voltage readings; disconnect the
digital voltmeter.
B3. Adjust Main Triggering Gate Tunnel Diode Bias
a. Disconnect the delay line cable at connector
J170.
b. Connect the digital voltmeter between TP155
and chassis ground.
c. If TRIG'D light is on and waveform display is
stable, adjust Gate TD Bias, R155, counterclockwise
until TRIG'D light just goes out.
d. Record the voltage at TP155.
e. Adjust-Gate TD Bias, R155, until TRIG'D light
just goes out; then clockwise until waveform display is
stable. Record the voltage at TP155.
f. Adjust-Gate TD Bias, R155, for the average of
the two recorded voltage readings obtained in parts d
and e of this step; disconnect the digital voltmeter.
B4. Adjust Main Triggering Internal DC Balance
a. Set the MAIN TRIGGERING COUPLING to
AC; set the LEVEL control to "0".
b. Adjust-Int DC Bal, R25, for a stable crt display
at graticule centerline (TRIG'D light on). See Fig. 5-9 for
reference.
TD Bias, R145,
Performance Check/Calibration-7B92A
Fig. 5-9. DC balance. (Circle denotes correct trigger
point.)
B5. Adjust Main Triggering Sensitivity
a. Adjust-Trig Sens, R125, for a sweep trigger
point at approximately 0.5 division from bottom of
waveform as MAIN TRIGGERING LEVEL control is
rotated through negative (-) portion of its range. See Fig.
5-10 for reference.
B6. Adjust Main Triggering External DC Balance
a. Set the MAIN TRIGGERING SOURCE to EXT.
b. Adjust-Ext DC Bal, R59, for a sweep trigger
point at graticule centerline. See Fig. 5-9 for reference.
B7. Check Main Triggering Level Range
a. Set MAIN TRIGGERING SOURCE to EXT.
Fig. 5-10. Trigger sensitivity (Circle denotes correct
point)
5-26