Tektronix 7623, Instruction Manual

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Calibration —7623/R7623 Service
h. ADJUST-Adjustment for R447 for correct tolerance
in both parts d and h.
V 14. Check Vertical Linearity
a. Remove the mainframe standardizer calibration fix­
ture. Install the 7A15A in the left vertical compartment
and connect a 0.4 volt square-wave signal from the
CALIBRATOR out jacks. Set the VERT MODE switch to
left.
b. Set the 7A15A Volts/Div switch to 0.2 volt/division.
Adjust the position control to keep the display centered on
the graticule and adjust the Variable Volts/Div control for a
two division display.
V c. CHECK—Position the two divisions of display
vertically and check for not more than 0.1 division of
compression or expansion anywhere within the graticule
area. Remove the 7A15A and install the mainframe
standardizer calibration fixture.
15. Adjust Vertical High-Frequency Compensation
a. Set the calibration fixture Test switch to VERT or
HORIZ +STEP RESP, REP RATE switch to 250 kHz, and
adjust the Amplitude control for a six-division display.
b. Set the 7B53A for a calibrated sweep rate of five
nanoseconds/division (use X10 magnifier). Set the trigger
source switch internal adjust trigger level control and
position control for a stable display, centered on the
graticule.
c. CHECK—Check for optimum square corner and flat
top on displayed pulse with aberrations not to exceed ±0.1
or -0.1 division with total peak-to-peak aberrations not to
exceed 0.1 division.
TABLE 2-2
High-Frequency Compensation
Adjustment
Primary Area
Of Pulse Affected Best Sweep Rate
C420 and R421
First 50
nanoseconds
50 nanoseconds/
division
C425and R425
First 20
nanoseconds
20 nanoseconds/
division
C427 and R427
First 5
nanoseconds
20 nanoseconds/
division
f.
Set the VERT MODE switch to RIGHT.
g. CHECK- Optimum square leading corner and flat top
on the displayed pulse with aberrations not to 0.1
or -0.1 division, with total peak-to-peak aberrations not to
exceed 0.1 division.
h. ADJUST— If necessary, compromise the adjustment
of C420, R421, C425, C427, and R427 for best response
from both the left and right vertical compartments.
i. To verify correct high-frequency compensation, per­
form the bandwidth check as given in next step.
V 16. Check Vertical Amplifier Bandwidth
a. Connect the high-frequency constant-amplitude signal
generator to the CW In connector of the mainframe
standardizer calibration fixture.
b. Set the Test switch of the calibration fixture to
VERT or HORIZ FREQ RESP.
d. Adjust-High-frequency compensation as given in
Table 2-2 for optimum square leading corner and flat top
with minimum aberrations within limits given in part c.
Location of adjustments is shown in Fig. 2-3. Use the low
capacitance screwdriver to adjust the variable capacitors.
Repeat the complete adjustment procedure several times to
obtaim optimum adjustment.
c. Set the 7B53A for a sweep rate of 0.2 microsecond/
division.
d. Set the high-frequency generator for six divisions of
deflection, centered on the graticule, at a reference fre­
quency of 3 megahertz.
e. Remove the calibration fixture from the left vertical
compartment and install it in the right vertical compart­
ment.
e. Without changing the output amplitude, increase the
output frequency of the high-frequency generator until the
display is reduced to 4.2 divisions (—3 dB point).
2-13