Tektronix 502 series, Instruction Manual

Page: 54 / 114

6. Astigmatism. Place the HORIZONTAL DIS­
PLAY switch in the 2-EXT VOLTS/CM position,
and rotate both the UPPER BEAM and LOWER
FOCUS controls fully clockwise. Position both
beams onto the screen, and adjust the ASTIG
UPPER and ASTIG LOWER controls so that both
defocused spots are as nearly circular as is possi­
ble. Adjust the UPPER BEAM and LOWER BEAM
FOCUS controls so that both spots are in sharp
focus.
7. INT BAL. Adjust the oscilloscope controls to
obtain a sweep and display both beams on the
face of the crt. Roughly adjust the INT BAL con­
trol so that both beams appear to have the same
intensity. For a fine adjustment, rotate the IN­
TENSITY control counterclockwise until the traces
are just visable. Adjust the INT BAL control until
both traces have the same intensity.
HORIZONTAL AMPLIFIER
Fig. 6-5. Adjustment of the X20 control.
The X20 CAL control is adjusted in step 8 of the re­
calibration procedure for the correct magnified sweep
rate. The control should be set so that markers occur
at 2 centimeters intervals.
8. X20 CAL. Place the TIME/CM control at 1
MlLLISEC and the HORIZONTAL DISPLAY switch
at X20. Apply 100/xsec markers to the upper
beam vertical input. Adjust the X20 CAL control
for one 100 //.sec marker per 2 cm.
9. XI CAL. Set the HORIZONTAL DISPLAY
switch at NORMAL (XI) and apply 1 millisecond
markers to the upper beam vertical input. Adjust
the XI CAL control for one 1 millisecond marker
per centimeter. Disconnect the markers.
10. NORM/MAG REGIS. Place the HORIZON­
TAL DISPLAY switch in the X20 position and posi­
tion the start of the upper trace under the verti­
cal centerline of the graticule. Rotate the HORI­
ZONTAL DISPLAY switch to NORMAL (XI) and
adjust the NORM/MAG REGIS control so that
the start of the sweep again lies under the verti­
cal centerline of the graticule. Repeat adjust­
ments 8, 9, and 10 until all are set correctly.
11. EXT HORIZ AMPL DC BAL. Rotate the
HORIZONTAL DISPLAY switch through the EXT
VOLTS/CM positions and adjust the EXT HORIZ
AMPL DC BAL control so that there is no hori­
zontal shift of the spots as the HORIZONTAL
DISPLAY switch is rotated.
12. C311. Set the TIME/CM switch at 1 ^SEC
and the HORIZONTAL DISPLAY switch at NOR­
MAL (XI). Rotate the TRIGGERING LEVEL con­
trol to the RECURRENT position. Connect a
probe from a test scope set for dc coupling to
pin 1 of V324. Adjust C311 so that the bottom
portion of the waveform displayed on the test
oscilloscope is flat.
M A
A
I
I I I *
A
/
I
1 7
r '
t 7
i l l ! 1 1 1 u
1 7
j
A B C
Fig. 6-6. Adjustment of C311.
Waveforms A and C result from improper settings of C 31 1. Capacitor C311
should be adjusted so that waveform B is obtained on the test oscilloscope.
6-4
RECALIBRATION PROCEDURE — TYPE 502