Rear Access Terminals; Perating Plates - HP 120A Operating And Servicing Manual

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Sect. II Page 4
out regard for the de level involved. In the AC po ­
sition the input signal (vertical or horizontal) is cou ­
pled to the amplifier through a capacitor which re ­
moves the de component from the input wave. This
coupling circuit has a low frequency cut-off at 2 cps;
however, to avoid degrading input pulses or square
waves below 200 cps it is advisable to use de coupling.
WHEN USING DC C UPLING THE AVERAGE VALUE
F THE DC DETERMINES THE P SITI N F THE
SWEEP N THE SCILL SC PE. IF Y U ARE UN ­
ABLE T FIND THE SWEEP WITH THE VERTICAL
P SITI N C NTR L WHEN USING DC C UPLING,
CHECK THE AVERAGE DC LEVEL T SEE THAT
IT ISN'T T
HIGH THEREBY DEFLECTING THE
BEAM
FF F THE SCREEN. When AC coupled the
maximum de that may be applied is 600 v.
A terminal for CRT intensity (Z-axis) modulation.
IF
Basic operating procedures are illustrated in the
drawings that follow. Directions are given for the
cabinet model but are the same for the rack mount
model except that the placement of the controls is
different.
The first two procedures are complete. The others
are arranged to supplement the first two by showing
the variations possible in using the oscilloscope. An
index to these illustrations follows:
. 2-11
OPERATING PLATE
N TE
An external capacitor must be connected in the in-
FIG.
put lead to the middle input terminal (see Figure 2-5)
if balanced ac coupling is used, since a de signal on
2-3
this terminal will unbalance the amplifier and might
2-4
throw the pattern off of the screen.
2-5
-------------
2-6
2-7
2-8
2-10
REAR ACCE
TERMINAL
£-9
2-10
The following terminals are accessible through the
2-11
rear access port of the instrument cabinet:
2-12
2-13
2-14
Horizontal and vertical deflection plates.
TITLE
Internal Sweep-Internal Synchronization
Internal Sweep-External Synchronization
AC Coupling Balanced Input
External Horizontal Input
Vertical Balance Adjustment
Vertical Sensitivity Calibration
Internal Sweep Magnification
Intermediate Calibration
Connection to Deflection Plates
Intensity Modulation
peration
Aligning Scope Trace with Graticule
Connecting External Condensers to
Extend Sweep Time.

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