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(b) Place the oscilloscope in the normal operating posi-
tion with respect to the poles of the earth.
(c) T u r n the C R T by the cover until the bright line is
aligned horizontal on the screen. T h e C R T should be
in close contact with the scale plate.
(d) After alignment, retighten the clamping screws (16)
alternately and uniformly making sure that the bright
line horizontal alignment is not changed.
C A U T I O N :
Be careful not to touch the C R T printed circuit board,
C R T socket, polyethylene-coated cable and other high
voltage circuits. When checking into this section, never
fail to turn power off and discharge the stored high
voltage.
ADJUSTMENTS
1. DC B A L adjustment:
If the waveform becomes out of center or the bright line
shifts up and down as the V . G A I N (11) is turned, it
should be corrected by adjusting D C B A L ( 1 3 ) .
In this adjustment, the V E R T A T T (4) must be set to
G N D , the V . G A I N (11) to the fully counterclockwise
position, and the ^ P O S I T I O N (12) to a point at which
the bright line is aligned in the center of the scope.
Then turn the V . G A I N (11) clockwise and, if the bright
line deviates, adjust the DC B A L (13) with a small
screwdriver so that the deviation is just made up for
toward the center of the scope, the same condition as at
the full counterclockwise position of the V . G A I N ( 1 1 ) .
Repeat this adjustments until the bright line stays
unchanged in both the clockwise and counterclokwise
positions of the V . G A I N ( 1 1 ) .
Adjustment of DC balance should begin approximately
15 after switch-on and the oscilloscope has become
stable.
2. Adjustment of V E R T . A T T
Remove the bottom plate.
square wave to the A C terminal (1) and the G N D ( 2 ) .
Set the V E R T A T T (4) to the 1 position and adjust
the signal generator so that an amplitude of approxi-
mately 4 cm is obtained on the scope with the V . G A I N
(11) in the fully clockwise position.
Set the S W E E P
R A N G E
100Hz to
1kHz and obtain
waveform on the scope. Make sure that the waveform is
ideal and shift the V E R T A T T (4) to the 1/10 position.
Increase the generator output by 20dB so that the
waveform is approximately 4 cm in amplitude.
waveform in this case is distorted, adjust the trimmer
capacitor T C 1 for an ideal waveform.
Use an insulated screwdriver for adjustment.
shift the V E R T A T T (4) to the 1/100 position and
adjust T C 2 for the same purpose.
12
Supply a 1kHz (approx.)
(6) to a position
between
two
to four peaks of
If the
Further
Other adjustment
When a 100kHz square wave is applied to the A C
terminal (1) and G N D ( 2 ) , the overshoot is corrected by
adjusting T C 3 .
The variable resistor V R 4 is a vertical position control.
With the $ P O S I T I O N (12) set to the center position,
adjust it until the bright line comes in the center of the
scope. T h e variable resistor V R 6 is also used to set the
bright line in the center of the scope, while V R 8 is used
to adjust the sweep width on the scope to approximately
10 cm.
Fig. 15 Location of trimmer and semi-fixed
variable resistors
Ideal waveform
Waveform for large trimmer capacitor
Overshoot (%) = —
Waveform for small trimmer capacitor
Vertical frequency response at high-frequencies
(For example, it becomes 9 0 0 k H z , —3dB)
Fig. 18 Square wave characteristic ajustment by trimmer
capacitor
x 100
a
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