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Model 1740A
Operation
SECTION Ill
OPERATION
3-1.
INTRODUCTION.
3-2.
This section provides general operating instruc-
tions for Model 1740A. Front- and rear-panel controls
and connectors are identified and described in figure
3-1. An initial turn-on procedure, operators calibration,
trigger selection table, and procedures for obtaining
basic displays are also included. The index numbers
after control and connector names in the text are keyed
to figure 3-1.
3-3.
TURN-ON PROCEDURE.
Before
turning
on
the oscilloscope,
read
the safety summary
located at the front
of this manual.
3-4.
To turn on the Model
1740A, perform the fol-
lowing steps:
a.
Turn all control knobs to the 12 o'clock posi-
tion except verniers @ and SWEEP
VERNIER
should be in CAL position; TRIGGER
HOLDOFF
on MIN. MAIN TIME/DIV @ fully clockwise.
b.
Verify pushbuttons
out except
A@, AQ,
and MAIN @
c.
Press LINE
switch @; LINE
indicator @
should light. After CRT warm up, a free-running trace
should be observed near center screen.
d. Increase (or decrease) BEAM INTENSITY @
to comfortable viewing level, and adjust FOCUS
5 | as
necessary for sharpest trace.
3-5.
OPERATOR
CHECKS.
3-6.
A few checks and adjustments may be required
to verify that the Model 1740A is operating properly.
If the oscilloscope is moved from one electromagnetic
environment
to another, the trace alignment
control
may need adjustment to align the horizontal trace with
the
graticule.
Astigmatism
and
focus
controls
may
need adjustment to obtain the sharpest display. Probe
compensation
may
be
required,
since
total
input
resistance and capacitance can vary slightly from one
oscilloscope to another.
3-7.
Adjust trace alignment as follows:
a.
Obtain a display as described in the turn-on
procedure.
b. With vertical POSN
control @, align trace
with center graticule line.
c. With a screwdriver, adjust TRACE ALIGN @
(on rear panel) for best trace alignment with graticule
line.
3-8.
Adjust astigmatism and focus as follows:
a.
Select
A VS B @ and lower BEAM
INTEN-
SITY @ to a low level.
b.
Position spot near center of CRT with POSN
@ and POSITION @ controls.
c.
Adjust
FOCUS
5 ] and
ASTIGMATISM
©
(on rear panel) for the smallest round spot.
3-9.
Perform
probe
compensation
adjustment
as
follows:
a.
Connect
probe to be compensated
to appro-
priate vertical INPUT connector 21) and the CAL 1 V
output @.
b. Set VOLTS/DIV @ to 0.1, MAIN TIME/DIV
©
to 0.2 mSEC, and input coupling @ to DC.
c.
Adjust main TRIGGER LEVEL @ fora
stable
display of the calibrator square-wave voltage. Display
should have flat tops. Any distortion in presentation
is caused by incorrect probe compensation.
d.
If overshoot
or
undershoot
is present,
turn
screwdriver
adjustment
in probe for a flat-top pre-
sentation (see figure 3-2).
3-10.
Perform vertical accuracy check as follows:
a.
Set controls to positions indicated in turn-on
procedure.
b.
Apply CAL1V
® signal to channel
AINPUT
connector
using
a BNC
to banana
plug adapter
and a test lead with alligator clips.
c.
Adjust channel
A VOLTS/DIV
@ to 0.2 V/div
and MAIN
TIME/DIV
@ to 0.2 mSEC/div.
Square-
3-1
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