Tektronix 2A60 Instrument Reference Book page 25

TYPE 2A60 AMPLlf IER
INTRODUCTION
The Type 2A60 Amplifier module, Fig. 1, is designed for
use with Tektronix Type 560-Series Oscilloscopes; however,
digital information will not be available on the Type 567
when the Type 2A60 is used. It has a bandpass of de to
equal to or less than -3 dB at one megacycle. Sensitivity is
adjustable in 4 calibrated steps from .05 volt (50 millivolts) to
50 volts per division of deflection and is continuously vari-
able, uncalibrated, between these steps and up to about
500 volts per division. Accuracy is within +3
%
at each of
the calibrated steps. The Type 2A60 module has an approxi-
mate input impedance of 1 megohm paralleled by 47 pico-
farads. Maximum allowable input signal is 600 volts {de plus
peak ac).
This manual includes operating instructions, circuit descrip-
tion, troubleshooting information, and calibration procedures
for the Type 2A60 module. For instructions and information
regarding the oscilloscope as a whole, refer to the oscillo-
scope manual.
Operating
Instructions
Throughout the instructions that follow, it is assumed,
unless otherwise noted, that the Type 2A60 module is in-
serted in the Y-axis opening of a Type 560-Series Oscillo-
scope, thereby providing vertical deflection of the oscillo-
scope trace.
If the module is inserted in the X-axis open-
ing, it will provide horizontal deflection of the trace and
the instructions must be interpreted accordingly. It is further
assumed that there is a time-base or sweep module in the
X-axis opening of the oscilloscope.
Signal Connections
The signal to be displayed is applied to the INPUT con-
nector on the front panel of the module. For best results,
the signal should be applied through a shielded cable,
with the cable shield connected to the chassis of both
the oscilloscope and the signal source. Leads should be
kept as short as possible.
High-impedance attenuator probes are available for
use with the Type 2A60 module. These probes reduce the
resistive and capacitive loading effect of the module and,
at the same time, attenuate the signal to allow display
of larger signals than would otherwise be possible. These
probes and other accessories are described in the Acces-
sories section of the oscilloscope manual.
Displaying a Signal
To display a signal with the Type 2A60 module, proceed
as follows:
1. Apply the signal, preferably through a shielded cable
or an attenuator probe, to the INPUT connector.
2. Establish a common ground between the oscilloscope
and the signal source. This can be done by connecting
the ground clip on a Tektronix attenuator probe to signal
ground.
3. Adjust the time-base controls to obtain a stable dis-
play of the signal.
4. Set the VOLTS/DIV. switch and the POSITION con-
trol so that the signal is placed as desired on the graticule.
In general, if you are interested only in the ac component
of the signal, you should set the AC-DC-GND. switch to
AC; if you are interested in the de level of the signal,.
you should set the AC-DC-GND. switch to DC. An excep-
tion to this is in observing low-frequency ac signals. When
the AC-DC-GND. switch is in the AC position, the lower
bandpass limit (3-db point) of the module is about 1.6 cps;
therefore, the best response to signals containing compo-
nents of less than about 2 cps (0.2 cps with a lOX attenu-
ator probe) will be obtained with the AC-DC-GND. switch
in the DC position.
Probe Compensation
If an attenuator
probe is used, its capacitance must be
compensated to that of the module for best signal response.
To compensate a Tektronix attenuator probe, proceed as
follows:
l. Display several cycles of the calibrator waveform on
the crt, using the attenuator probe.
2. Adjust the variable capacitor in the body of the
probe to obtain a square leading corner on the positive
half cycles (see Fig. 2).
Gain and DC Balance Adjustments
Any time you move the Type 2A60 module from one
oscilloscope opening to another you must adjust the gain
to compensate for differences in crt deflection sensitivities.
This should also be done from time to time even if the
module has not been moved. In addition, the de balance
of the module should be checked and adjusted, as nec-
essary, from time to time.
To properly set the gain of the Type 2A60 module, pro-
ceed as follows:
1. Set the AC-DC-GND. switch to DC, the VOLTS/DIV.
switch to .05, and the VARIABLE control fully clockwise
(to the CALIBRATED position).
2. Display a 0.2-volt Calibrator signal on the crt and
adjust the front-panel GAIN ADJ. control for a deflection
of exactly 4 divisions; or, display a 100-millivolt Calibrator
signal and adjust the GAIN ADJ. control for a deflection
of exactly 2 divisions (the first method is preferred).
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