Tektronix 502A, Instruction Manual

Page: 46 / 110

Calibration Procedure — Type 502A
Fig. 5-4. Adjustment of the GEOM control. In waveform A the GEOM control is improperly set causing bowing of the vertical lines. In
waveform B the bowing of the vertical lines has been reduced to a minimum by the proper adjustment of the GEOM control.
vertical portions of the markers are displayed on the face
of the crt and adjust the TRIGGERING LEVEL Control to
obtain a stable display. Set the
GEOM control for minimum
curvature of the vertical lines at the sides of the crt.
8. Adjusting CRT HORIZ SENS BAL and
HORIZ BEAM REGIS
From the Type 180A apply 100 MICROSECONDS and 1
MILLISECONDS markers to the A input of the LOWER BEAM
and
the B input of the UPPER BEAM. Switch the UPPER
BEAM Input Selector to B-DC and the SENSITIVITY switches
of
both beams to 5 VOLTS PER CM. With the Vertical
POSITION Controls,
position the traces until the markers of
the LOWER BEAM are just touching the markers of the
UPPER BEAM.
Adjust the HORIZ BEAM REGIS until the first and ninth
time markers are
as near being above one another as
possible. Now adjust the CRT HORIZ SENS BAL until the
sensitivity of the two beams is the same. At this point in
the calibration the two beams are being matched to each
other and the time markers may not coincide with the
graticule marks.
NOTE
Every time the CRT HORIZ SENS BAL is adjusted
the INT BAL must be checked. The HORIZ BEAM
REGIS may also have to be readjusted at this time.
The above three controls interact with each other.
9. X1 CAL and X20 CAL Adjustments
Set the UPPER BEAM Input Selector to the A-DC position.
With 1 MILLISECONDS and 100 MICROSECONDS time
markers
applied to the A input of each beam reset the
HORIZONTAL DISPLAY switch to X20 position. Adjust the
X20 CAL for a display of one 100 MICROSECONDS time
marker per 2 cm. Now turn the HORIZONTAL DISPLAY
Switch to X1 and adjust the X1 CAL for one 1 MILLI­
SECONDS time marker every cm.
Fig. 5-5. Adjustment of the X20 control. The X20 CAL control is
adjusted in the calibration procedure for the correct magnified
sweep rate. The control should be set so that markers occur at
2 centimeter intervals.
There will be interaction between the X1 and X20 adjust­
ments. After this interaction has been removed the X2 and
X5 and X10 positions of the HORIZONTAL DISPLAY switch
should be checked. Disconnect the time markers.
5-4