Tektronix 7L18 Instruction Manual page 55

Calibration—7L18 Service
Variable Voltage Source
0 +12 volts
7000 Series Oscilloscope
O
O
O
qg ®
Ext In Horiz/Trig
2295-22A
Fig. 4-14. External Horizontal Input Voltage Test Setup.
c. Apply a variable voltage source, such as the variable
power supply, to the EXT IN HORIZ/TRIG pin-jacks and
adjust the voltage output so the beam is deflected the full
10-division span.
d. Check—the voltage source should equal +10 V +1 V.
NOTE
An alternate method using a sine wave to check
external sweep operation is as follows:
1. After the crt beam has been positioned to the
zero voltage reference as described in part b, apply a
1 kHz sine wave with an amplitude of 10 Vpeak (20 V
p-p, referenced at 0 V) to the EXT IN HORIZ/TRIG
connector.
2. The crt beam should sweep the full 10 divisions
(+0.1 division) of the graticule when the input
voltage is 10 V peak +7 V.
e. Disconnect the voltage or signal source tothe EXT IN
HORIZ/TRIG connector and returnthe TIME/DIV selector
to AUTO.
16. Check Video Output Level (500 mV +5% of video
signal per division of display above the baseline)
a. Connect the test setup as shown in Fig. 4-15. Apply
the VIDEO OUT signal of the 7L18 to the input of a dc-
coupled test oscilloscope with sensitivity set to 1 V/div.
Set the 7L18 Display Mode to LOG 2 dB/DIV,
REFERENCE LEVEL to —20 dBm, TIVE/DIV to AUTO,
FREQ SPAN/DIV to 100 kHz, and RESOLUTION
BANDWIDTH to 300 kHz.
b. Position the base of the CAL OUT signal on the
bottom graticule line of the 7L18 display using the
VERTICAL POSITION control and adjust the REF
VARiable control for eight divisions of signal amplitude.
c. Check the amplitude of the video output signal using
the test oscilloscope. Note the dc zero volt level. Video
amplitude should equal 4.0 volts +0.2 volt as measured
from the zero voltage reference level. See Fig. 4-16.
d. Disconnect the test equipment to the 7L18.
4-19