General Operating Information - Tektronix 7A13 Instruction Manual

Front Panel Adjustments
These adjustments must be accomplished each time
the 7A13 is placed in a different oscilloscope and should
be checked in the given sequence prior to any Critical
measurement of waveforms.
Preset 7A13 controls as follows:
COMPARISON VOLTAGE
+ INPUT Mode GND
— INPUT Mode GND
VOLTS/DIV 1V
VARIABLE In (CAL)
STEP ATTEN BAL Midrange or asis
GAIN As is
X10 BAL Midrange or asis
VAR BAL Midrange or asis
BW 5 MHz
POSITION Midrange
Allow 20 minutes warmup time.
VAR BAL Adjustment
1. Set the VOLTS/DIV switch to 1 mV.
2. Vary the VARIABLE control throughout its range
while observing the CRT trace.
3. Adjust VAR BAL so that there is no trace movement
while varying the VARIABLE control.
STEP ATTEN BAL Adjustment
1. Vary the VOLTS/DIV switch from 10 mV to 50 mV
while observing the CRTtrace.
2. Adjust STEP ATTEN BAL so that the trace does not
move while varying the VOLTS/DIV switch.
X10 BAL Adjustment
1. Set the VOLTS/DIV switch to 10 mV. Pull out the
PULL VAR FOR X10 Vc Range knob while observing the
CRT trace.
2. Adjust X10 BAL sothat there is no trace movement
while moving the knob in and out.
3. Repeat all balance adjustments until optimum set-
tings are achieved.
@
Operating Instructions—7A13 (SN B200000-up)
GAIN Adjustment
1. Using the POSITION control, position the CRT
trace two divisions below graticule center.
2. Set VOLTS/DIV to 1 mV position.
3. Apply a 4mV_ peak-to-peak calibrator signal
through a coaxial cable to the + INPUT connector on the
7A13.
4. Set the + INPUT Mode switch to DC.
5. Adjust GAIN control so that the display is four
divisions of square wave amplitude with the bottom of the
display at the reference established in step 1.
GENERAL OPERATING INFORMATION
Signal Connection
In general, probes offer the most convenient means of
connecting signals to the inputs of the 7A13. The
Tektronix probes are shielded to prevent pickup of
electrostatic interference. A 10X attenuator probe offers a
high input impedanceand allowsthe circuit under test to
perform very close to normal operating conditions. (For
further information on the use of probes, see Use of
Attenuator Probesin this section of the manual, and inthe
probe instruction manual).
In high-frequency applications requiring maximum
overall bandwidth, use a coaxial cable terminated at both
ends in the characteristic impedance of the cable. To
maintain the high-frequency characteristics of the applied
signal, use high-quality, low-loss cable. Resistive coaxial
attenuators can be used to reducereflections if the applied
signal has suitable amplitude.
High-level, low-frequency signals can be connected
directly to the 7A13 input with short unshielded leads. This
coupling method works best for signals below about one
kilohertz and deflection factors above one volt/division.
When this method is used, establish a common ground
between the 7A13 and the equipment under test (Common
ground provided by line cords is usually inadequate).
Attempt to position the leads away from any source of
interference to avoid errorsin the display. If interference is
excessive with unshielded leads, use a coaxial cable,
probe, or differential amplifier operation. (Differential
amplifier operation may require special considerations for
signal connections. See Differential Operation in this
section of the manual).
2-5