V E R T IC A L SYSTEM
Calibration—221 Service
Equipment Required
1. Probe tip to BNC adapter
4. Square-wave generator
2. Standard amplitude calibrator
5. Three-inch screwdriver
3. Constant amplitude signal generator
6. Low-capacitance screwdriver
Control Settings
Preset the controls as given in the Preliminary Control
Settings,
10. Check/Adjust Step Attenuator Balance (STEP
BAL)
a. Set the VO LTS/DIV switch to the 1 V position.
b. Position the trace to the horizontal center line.
c. Change the VO LTS/DIV switch to the 5 m position.
d. Check that the trace is w ithin 0.1 division of the
center horizontal line.
e. Adjust the STEP ATTEN BAL adjustment, R135, for
a trace at the horizontal center line. See Fig. 5-4.
f. Repeat part (a) through (e) until less than 0.1 division
shift is noted when changing the VO LTS /D IV setting.
11. Check/Adjust V O L T S /D IV V A R BAL
a. Set the trace to the center horizontal graticule line.
b. Set the VO LTS/D IV setting to 0.1 and the VO LTS/
DIV VAR to minimum counterclockwise direction.
c. Check that there is less than 0.1 division of trace shift
when varying the VO LTS/DIV VAR control.
d. Adjust the VAR VO LTS/DIV BAL adjustment for a
trace shift for no more than 0.1 division. See Fig. 5-5.
12. Check/Adjust Probe Compensation
a. Set the VO LTS/DIV switch to .1, and INPUT
COUPLING switch to DC.
b. Connect the square-wave generator to the 221. Use a
probe tip to BNC adapter, a 50-ohm term ination, and a GR
to BNC adapter.
c. Set the square-wave generator for a 5 kHz signal w ith
four divisons of display.
d. Set the SEC/DIV switch to .1 m. Adjust the LE V E L/
SLOPE control fo r a stable display, triggered on the
positive excursion of the waveform.
e. Check that the positive excursion of the displayed
square wave is fla t (flat top).
f. Adjust C l 12 for the best square-wave display (flat
top). See Fig. 5-4.
g. Leave test equipment connected.
Fig. 5-5. Location of the V O L T S /D IV Var Bal adjustments.
® t
REV. APR 1974
5-7
