HP 1740A - Operation; Introduction and Turn-On Procedure; Operator Checks and Adjustments

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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