Model 175A Section V
Paragraphs 5-1 to 5-12
SECTION V
MAINTENANCE
5 -1. INTR 0 DU CTION. c. Make the following settings on the Model 175A:
5- 2. This section covers routine maintenance, POWER .................. ON
troubleshooting, and adjustment of the Model 175A INTENSITY MODULATION .... INTERNAL
Oscilloscope. A performance check is included which SWEEP TIME ......... 1 MSEC/CM
may be used to verify proper operation of the instru- Sweep VERNIER ............. CAL
ment at incoming inspection or after adjustments HORIZONTAL DISPLAY ......... X1
have been made. EXTERNAL VERNIER ......... CAL
TRIGGER SOURCE ............ INT
5-3. SERVICING THE AIR FILTER. SWEEP MODE .......... FREE RUN
TRIGGER LEVEL ............. 0
5-4. Inspect the air filter at the rear of the instru- TRIGGER SLOPE ............. (+)
ment and clean it before it becomes clogged enough
to restrict the flow of cooling air. To clean, remove
the filter from the instrument and wash it thoroughly d. Depress BEAM FINDER to locate trace. With
in warm water and detergent. Dry thoroughly and BEAM FINDER depressed, center display with hori-
coat with a filter adhesive such as Filter Coat No. 3 zontal and vertical position controls.
from Research Products Company, Inc. This ad-
hesive is available from heating supply stores or from e. Release BEAM FINDER and turn INTENSITY
control clockwise, if necessary. A trace should ap-
your Hewlett-Packard sales representative. pear on screen.
5-5. PERFORMANCE CHECK. f. The INTENSITY control should vary the intensity
5-6. The performance check is intended to deter- of the display from extinguished to brighter than nor-
mine whether or not the instrument is operating with- mal intensity. Adjust INTENSITY for normal viewing
in its specifications. Should adjustment be required, level.
refer to paragraph 5-25. To check the vertical and
horizontal plug-in units, refer to the individual man- g. The FOCUS control should defocus the display
uals covering these instruments. at each extreme of the control and focus the display
at approximately midrange. Adjust FOCUS for
5-7. TEST EQUIPMENT. sharpest display.
5-8. Test equipment recommended for the per- h. Adjust SCALE control to align the trace parallel
formance check is listed in table 5-1, items 1 through to the horizontal graticule lines.
7. Similar instruments having the listed character-
istics may be substituted. 5-11. HORIZONTAL AMPLIFIER.
5-9. PRELIMINARY SETTINGS. 5- 12. SENSITIVITY.
5-10. Vertical and horizontal plug-in units must be a. Connect the Calibration Generator to HORIZ
in place to make the performance check. Set the 115- INPUT.
230 volt switch to the line voltage being used.
b. Set Calibration Generator output for 10 volts
a. If the vertical plug-in unit has more than one peak- to-peak.
channel, select CHANNEL A and use channel A con-
trols. Make the following settings on the panel of c. Set:
the vertical plug-in unit:
HORIZONTAL DISPLAY . . 1 VOLT/CM AC
AC-DC.. .................. AC EXTERNAL VERNIER. fully counterclockwise
SENSITIVITY .......... 2 VOLTS/CM
d. Horizontal deflection should be 1 cm or less.
VERNIER ................. CAL
e. Set:
b. Depending on model number, make the following
settings on the panel of the horizontal plug-in unit: EXTERNAL VERNIER .......... CAL
Model 1780A:
SWEEP OCCURRENCE. ... NORMAL f. Horizontal deflection should be 10 cm k0.5 cm.
Model 1781A/B: g. Set Calibration Generator output for 1 volt
SWEEP SELECTOR ... MAINSWEEP peak-to-peak.
Model 1782A:
FUNCTION ............. OFF h. Set:
Model 1783A:
TIME MARKER .......... OFF HORIZONTAL DISPLAY . 0.1 VOLT/CM AC
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