Tektronix 502 series, Instruction Manual

Page: 53 / 114

CALIBRATOR
2. R879, Calibrator Adjust. Connect the dc volt­
meter to the junction of R885 and the cathode of
V873 at the point where resistor R885 is con­
nected to the SQUARE-WAVE .CALIBRATOR
switch. (Refer to Fig. 6-3.) Adjust the Calibrator
Adjust control, R879, for a reading of +100 volts
on the dc voltmeter.
Fig. 6-3. Location of the Calibrator test point.
CRT CIRCUIT
3. HV ADJ. Connect the dc voltmeter to the HV
TEST POINT marked on the shield at the left rear
of the instrument. Set the HV ADJ control for a
reading of —2900 volts on the dc voltmeter.
4. CRT Alignment. Adjust the oscilloscope con­
trols to obtain a sweep and position one of the
traces under a horizontal division of the graticule
near the vertical center of the crt. Loosen the
clamp at the base of the crt, and using the
plastic handle provided at the base, rotate the
crt until the trace runs parallel to the horizontal
divisions of the graticule. Push the crt forward
against the graticule and tighten the crt clamp.
5. GEOM ADJ. Place both Input Selector
switches in the A DC position and connect 1-
millisecond time markers to both A inputs. Ro­
tate the TIME/CM control to the 1 MILLISEC posi­
tion and the HORIZONTAL DISPLAY switch to
the NORMAL (XI) position. Adjust the two
SENSITIVITY controls so that the markers cover
the entire screen vertically. Position the two
traces so that only the vertical portions of the
markers are displayed on the face of the crt and
adjust the TRIGGERING LEVEL control to obtain
a $table display. Set the GEOM ADJ control for
minimum curvature of the vertical lines at the
sides of the crt. Disconnect the time markers.
A
Fig. 6-4. Adjustment of the GEOM ADJ control.
In waveform A the GEOM ADJ 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 ADJ control.
© RECALIBRATION PROCEDURE — TYPE 502
6-3