Tektronix 492, 492P, Руководство по обслуживанию

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b. Set the step attenuators for 0 dB (with —21.5 dBm
input the signal level should be 7 divisions or more). Adjust
the generator output for a 7 division signal reference level.
c. Remove the 110 MHz signal to the 110 MHz filter and
reconnect P365.
d. Set the step attenuators for 21 dB; then apply the
110 MHz signal to the input (J321) of the 110 MHz IF ampli­
fier (Fig. 3-46).
e. Adjust the gain of the IF amplifier with R1015 for a
display amplitude that equals the seven division reference
set in part b.
f. Remove the 110 MHz signal and reconnect P321.
g. Apply the CAL OUT signal to the RF INPUT. Set the
REF LEVEL to -2 0 dBm. Center the 100 MHz calibrator
signal on screen then decrease the FREQ SPAN/DIV to
100 kHz with a RESOLUTION BANDWIDTH of 100 kHz.
Keep the calibrator signal centered on screen with the FRE­
QUENCY control.
h. Verify that band 1 Gain, R2031, is fully ccw. Set the
front panel AMPL CAL fully ccw.
i. Adjust the 110 MHz IF Gain, R1015, (Fig. 3-46) for a
signal amplitude of 5 divisions. (If this cannot be achieved, it
indicates excessive loss through the front end.)
j. Adjust AMPL CAL for a full screen signal. AMPL CAL
should now have
6
dB down range and at least
6
dB of up
range.
NOTE
Two variable capacitors, C325 and C2047, do not re­
quire adjustment during calibration. Procedure re­
quires return loss measurement which is a
maintenance and repair function.
14. Digital Storage Calibration
NOTE
This is a two-part procedure; the first can be used to
■ calibrate the 492/492P, the second is a program to be
used with TEKTRONIX 4050-Series Computer termi­
nal with the programmable 492P only.
a. Apply the CAL OUT signal to the RF INPUT and set
the front-panel controls as follows:
Calibration—492/492P Service Vol. 1 (SN B030000 & up)
Adjustment Procedure
FREQUENCY 200 MHz
FREQ SPAN/DIV 20 MHz
REF LEVEL -1 0 dBm
Vertical Display 10 dB/DIV
AUTO RESOLUTION On
TIME/DIV AUTO
Digital Storage (Option 02) VIEW A
b. Adjust the PEAK/AVERAGE cursor so it is about one
division above the bottom of the screen.
c. On the Horizontal Digital Storage board for SN
B043115 and above:
1) adjust Output Offset, R1039 (Fig. 3-47A), so the left
edge of the cursor is at the left edge of the crt (about
0.25 division over-span from the left graticule line);
2) adjust Output Gain, R1041 (Fig. 3-47A) so the right
edge of the cursor is at the right edge of the crt;
3) alternately switch VIEW A on and off while adjusting
Input Offset, R1046 (Fig. 3-47A), so the storage signal at
the left edge of the screen tracks with the non-stored
signal;
4) alternately switch VIEW A on and off while adjusting
Input Gain, R1048 (Fig. 3-47A), so the storage signal at
the right edge tracks with the non-store signal.
5) Repeat steps 3 and 4 until the storage signal matches
the non-stored signal on both edges of the screen.
On the Horizontal Digital Storage board for SIM B043114
and below:
1) adjust Horizontal Offset, R3041 (Fig. 3-47), so the left
edge of the cursor is at the left edge of the crt (about
0.25 division over-span from the left graticule line);
REV SEP 1983
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