Tektronix 1A2 User manual

INSTRUCTION
MAN OUAL
Tektronix, Inc.
S.W. Millikan Way @ P. O. Box 500 @ Beaverton, Oregon 97005 @ Phone [phone] @ Cables: Tektronix
070-0430-01
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[A2
PLUG-IN
466

http://manoman.sghill.com
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TYPE
1A2
DUAL-TRACE
PLUG-IN
UNIT
CALIBRATED “~~
7 PREAMP
.
POSITION
POSITION
CH1421N
ADD
ONLY
VAR
VAR
ATTEN
BAL
ATTEN
BAL
} . TRIGGER
SELECTOR
QD)
|
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cn
A©°
cue
ALT
cHoP
“a
VARIABLE
VARIABLE
VOLTS/CM
CH!
votts/
cM
)
5
2
5
:
8
TRIG
OUT
|
(05 /Puito
/ INVERT
puto
20
invert
BRATEO
a
SERIAL
©
CHANNEL
1
CHANNEL
2
AC pc
GND
AC
pc
GND
INPUT 2
PORTLAND,
OREGON,
U.S.A.
y,
TEKTRONIX,
Fig. 1-1. Type 1A2 Dual Trace Plug-In Unit.

SECTION I
CHARACTERISTICS
Introduction
The Type 1A2 Dual-Trace Plug-In Unit contains two identi-
cal fast-rise calibrated preamplifier channels. Either chan-
nel can be used independently, or electronically switched to
produce dual-trace displays. In addition, both channels can
be combined at the output, adding or subtracting according
to the settings of the polarity switches.
Each channel has its own input coupling, attenuator, gain,
polarity and position controls which allows each display to
be adjusted independently for optimum viewing.
There are two modes of dual-trace operation: Chopped
or Alternate. In the chopped mode, an internal multivibra-
tor switches the channels at a free-running rate of about
220 kHz. In the alternate mode, the oscilloscope time-base
generator internally switches the channels at the end of each
sweep during the retrace interval.
The Type 1A2 can be used with any of the Tektronix 530-,
540-,
or 550-series Oscilloscopes. It can also be used with
the 580-series Oscilloscopes in conjunction with the Type 81
or 81A Plug-In Adapter. The Type 1A2 can also be used with
other oscilloscopes and devices through the use of the Type
127, 132, or 133 Plug-In Power Supplies.
CALIBRATED PREAMPLIFIER
Characteristic Performance Requirement
Supplemental Information
Deflection Factor
.05 volts/cm to 20 volts/em in 9 calibrated
steps for each channel
Steps in 1-2-5 sequence
Deflection Accuracy Within =&3% of indicated deflection with
VARIABLE control fully clockwise
With gain correct at .05 V/cm
Variable Deflection Factor
Uncalibrated deflection factor at least 2.5
times the VOLTS/CM switch indication. This
permits continuous (uncalibrated) adjustment
from 0.05 volts/em to at least 50 volts/cm.
Frequency Response (not more
than 3dB down): Type 1A2
with Tektronix oscilloscope;
544, 546, or 547 DC to 50 MHz
581, 581A, 585, 585A DC to 50 MHz with Type 81A Plug-In Adapter
DC to 33 MHz with Type 81 Plug-in Adapt-
er
541, 541A, 543, 543A, 545, | DC to 33 MHz
545A, 545B, or 555
551 DC to 27 MHz
531, 531A, 533, 533A, 535, | DC to 15 MHz
or 535A
536 DC to 11 MHz
Risetime: Type 1A2 with Tek-
tronix oscilloscopes;
544, 546, or 547 7 ns
‘581, 581A, 585, 585A
7 ns with Type 81A Plug-In Adapter
11 ns with Type 81 Plug-in Adapter
541, 541A, 543, 543A, 545. | 11 ns
545A, 545B, or 555
551 13 ns
531, 531A, 533, 533A, 535, | 24 ns
or 535A
536 32 ns
Input RC Characteristics
Typically 1 MQ parallel with approximately
15 pF
Maximum Input Voltage
600 volts combined DC and peak AC; 600
volts peak-to-peak AC
Input Coupling Modes AC or DC, selected by front-panel switch
GND, disconnects
amplifier input
signal and grounds
@i 1-1

Characteristics—Type 1A2
Characteristic
Performance Requirement
Supplemental Information
AC Low-Frequency Response Typically 3 dB down at 2 Hz direct; 0.2 Hz
with 10 probe
Display Modes Channel 1 only
Channel 2 only
Dual-trace, alternate between channels. Dual-
trace, chopped between channels. Added
algebraically
Chopped Repetition Rate 220 kHz 20% rate to show successive 2 us
segments of each trace
Common Mode Rejection Ratio 20:1 for common-mode signals up to 10cm in
amplitude
With optimum GAIN adjustment for both
channels
Polarity Inversion
Signal on either Channel 1 or 2 can be
inverted
Output Trigger? Measured at TRIG OUT connector
Output Trigger Voltage
Approximately 0.5 V/cm or gain of 10 VOLTS/CM at .05
Bandwidth Low-Frequency 3 dB down is about 10 Hz when
output of the amplifier is working into 1 MQ;
High-Frequency 3dB down is amplitude
dependent and shown in the graph of Fig. 1-2
Output Coupling AC
1Applies only to instruments with a serial number of 716 or higher.
MECHANICAL CHARACTERISTICS ACCESSORIES
Characteristic Information . ; . . .
CG i Alumi i hassi Standard accessories supplied with this instrument will be
onstruction Uminumeal’oy Chassis found in the Mechanical Parts List. For optional accessories,
Finish Anodized front panel see the current Tektronix, Inc. catalog.
10
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6 \
5
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4
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6 N
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2 \
2 N
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2 |
6 9 =
o 8 AN
& 47
z AN
F
6
\
\
5
4 \
\
3 \
2
1 2 3 4 5 6 7
Frequency in MHz at 3 dB down
Fig. 1-2. Type 1A2 Trigger output amplitude and High-Frequency Response (3 dB down).

SECTION 2
OPERATING INSTRUCTIONS
FUNCTIONS OF FRONT-PANEL CONTROLS
The functions of all controls, adjustments and connectors
except the MODE and TRIGGER SELECTOR switches are
identical for both channels.
POSITION
PULL TO
INVERT
GAIN
VAR ATTEN
BAL
MODE
VOLTS/CM
VARIABLE
AC-DC-GND
TRIGGER
SELECTOR?
TRIG OUT*
Positions the trace vertically on the CRT.
Only the Channel 1 POSITION controls
position in the ADD mode.
A two-position switch that presents the
display in a normal or inverted polarity
with respect to the applied signal.
A screwdriver adjustment that calibrates
the basic deflection factor of the channel.
A screwdriver adjustment for setting the
amplifier DC levels so the trace does not
shift position under no-signal conditions
as the VARIABLE VOLTS/CM control is
turned.
A five-position switch that sets the mode
of operation as follows:
ALT—Dual-trace alternate mode of opera-
tion (triggered electronic switching between
channels during the beam retrace interval).
CH 1—Selects the use of Channel 1 only.
ADD—Permits adding the outputs of the
two channels algebraically.
CH 2—Selects the use of Channel 2 only.
CHOP—Dual-trace chopped mode of oper-
ation (free-running electronic switching of
channels at about a 220-kHz rate).
Nine-position switch to select the calibrated
vertical-deflection factors.
Provides overlapping variable uncalibrated
attenuation between the calibrated deflec-
tion factors and extends the attenuation
range to about 50V/CM.
Three-position switch to provide either AC-
or DC-coupled input into the amplifier. A
third
position (GND) connects the ampli-
fier input to ground without grounding the
input signal.
Determines whether the Channel 1 or Chan-
nel 2 signal is applied to the Trigger
Amplifier.
Output signal of the Trigger Amplifier.
Permits the use of Channel 1 or 2 as an
external trigger source.
FIRST TIME OPERATION
The following procedure will help you become familiar
with the Type 1A2 operation.
1. Insert the Type 1A2 into the oscilloscope, tighten the
securing rod and turn on the oscilloscope power.
2. Allow about 2 to 3 minutes warm-up time and free run
the oscilloscope sweep at 0.5 sec/cm.
3. Set the applicable Type 1A2 front-panel controls for
both channels as follows:
AC-DC-GND DC
VOLTS/CM .05
VARIABLE CALIBRATED
PULL TO INVERT Pushed in
POSITION Centered
MODE CH 1
TRIGGER SELECTOR? CH 1
4. Position the trace about one centimeter above the grati-
cule centerline with the Channel 1 POSITION control.
5. Place the MODE switch to CH 2 and position the trace
one centimeter below the graticule center line with the
Channel! 2 POSITION control.
6. Place the MODE switch to ALT. Both Channel 1 and
2 traces should be displayed.
7. Set the oscilloscope Time/Cm switch to 50 msec. Note
that for each sweep cycle one channel is displayed and the
other is shut off. Electronic switching from one channel to
the other occurs during the retrace interval.
8. Set the MODE switch to CHOP. Notice that both traces
seem to start simultaneously and continue across the CRT.
9. Set the oscilloscope Time/Cm switch to 5ysec and
adjust the oscilloscope trigger controls to obtain a stable
display. Notice that each trace is composed of many short-
duration bits or segments with visible switching transients
existing between channels (see Fig. 2-1A).
10. To see the chopped-mode switching action clearly,
increase the sweep rate to 1 wsec/cm. Notice that Channels
1 and 2 are alternately on and off at about 2 us intervals.
(See Fig. 2-1B.) Chopping rate is determined by the free-
running multivibrator switching rate and is about 220 kHz.
11. Blank out the switching transients between channels
by setting the CRT Cathode Selector switch (located on the
rear panel of most Tektronix oscilloscopes) to the Dual-Trace
Chopped Blanking position (see Fig. 2-1C).
12. Set the oscilloscope Time/Cm switch to 0.5 msec. Using
coaxial cables, a T connector connected to Channel 1 and
a connector adapter {if needed), apply 0.1 volt from the
oscilloscope Amplitude Calibrator to the Channel 1 and 2
input connectors.
13. Set the trigger controls for +internal (plug-in) trigger-
ing or connect a jumper coaxial cable from the TRIG OUT
connector! to the oscilloscope Trigger Input connector and
1Applies only to instruments with a serial number of 716 or higher.
2-1

Operating Instructions—Type 1A2
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Fig. 2-1. Chopped-mode waveforms: (A) trace broken up into
segments, (B) chopped-mode switching action from channel to
channel, and (C) switching transients blanked out.
set the trigger controls for + external triggering. Both Chan-
nel 1 and 2 should display the calibrator waveform. Each
waveform should be 2 cm in amplitude.
NOTE
If the waveforms are not exactly 2 cm in amplitude,
overlook the inaccuracy until completing this oper-
ating procedure. Subsequent paragraphs describe
how to properly set the gain of the unit.
14. Set the MODE switch to ADD. There should be one
waveform display 4¢cm in amplitude. This is the addition
of the Channel 1 and 2 signals (2cm each), Notice that
only the Channel 1 POSITION control will move the display
vertically.
15. Pull out the Channel 1 PULL TO INVERT switch and
free run the time base. The display should be a straight
2-2
line, indicating the algebraic difference between the two
signals. Since both signals have equal amplitudes and wave-
shape, the difference is zero.
NOTE
If the display is not a straight line, this indicates
that the gains of the channels are not matched.
This may be overlooked until this operating pro-
cedure is completed. Subsequent paragraphs
describe how to properly set the gain of each
channel.
Before the Type 1A2 is used for accurate measurements,
the GAIN and VAR ATTEN BAL for each channel should be
adjusted. These adjustments are described in the following
paragraphs.
Gain Adjustments
The gain adjustments should be checked periodically to
assure correct vertical deflection factors, particularly when
the Type 1A2 is used for the first time or is moved from one
oscilloscope to another. Use the following procedure to
check the gain of each channel:
1. Set the applicable Type 1A2 front-panel controls for
both channels as follows:
AC-DC-GND DC
VOLTS/CM .05
PULL TO INVERT Pushed in
POSITION Centered
VARIABLE CALIBRATED
MODE CH 1
TRIGGER SELECTOR CH 1
2. Set the oscilloscope sweep rate and triggering controls
for a 0.1 msec/cm free-running sweep.
3. Apply a 0.2-volt peak-to-peak signal from the oscillo-
scope calibrator through a coaxial cable to the Channel 1
Input connector.
NOTE
For maximum accuracy use a calibrator signal
source which has an amplitude accuracy of better
than 3%.
4. The resulting display should be exactly 4m in ampli-
tude. If not, set the Channel 1 GAIN for the correct wave-
form amplitude. (Use the Channel 1 POSITION control to
align the display with the graticule markings.}
5. Set the MODE switch to CH 2 and apply the calibrator
signal to the Channel 2 input connector.
6. The display should be exactly 4cm in amplitude. If
not, adjust the Channel 2 GAIN contro! for the proper display
amplitude. Use the Channel 2 POSITION control to align the
display with the graticule markings.
7. Disconnect the calibrator signal.

Operating Instructions—Type 1A2
502 coaxial cable
with GR connectors
P6034 or
P6035, Probe
Y
ye _-Y ge
X = GR Type 874
Connectors
Optional Items
‘Select length which will move small reflection (due to
input Z of Type 1A2) out of area of interest.
*Used to reduce reflection by a factor of 4. Doubles
probe attenuation factor.
Used to reduce bulk on front of the Type 1A2.
GR Type 874-K
Coupling Capacitor
017-0028-00
‘50.9
GR
2X
GR-to-BNC
I
type
1A2
Attenuator
Adapter
|
Input
017-0046-00
017-0064-00
Let
yet:
|
‘Short
50
{2
coaxial
50
{2
BNC
I
cable
with
GR
Termination
|
connectors
011-0049-00
I
017-0505-00
|
Fig. 2-2. Using the P6034 or P6035 Probe with the Type 1A2.,
Variable Attenuator Balance Adjustments
If the VAR ATTEN BAL control of a channel is not properly
set, the position of a no-signal free-running trace will shift
vertically as the VARIABLE control is turned. If there is
a trace shift, set the VAR ATTEN BAL adjustment for each
channel as follows:
1. Set the Type 1A2 front-panel controls to the same
positions as in the Gain Adjustments procedure except the
AC-DC-GND switch must be set to GND and the MODE
switch to ALT.
2. Carefully adjust the Channel 1 VAR ATTEN BAL control
to a point where there is no trace shift as the Channel 1
VARIABLE control is turned back and forth through its full
range.
3. Carefully adjust the Channel 2 VAR ATTEN BAL control
to a point where there is no trace shift as the Channel 2
VARIABLE control is turned back and forth through its full
range.
4. Due to interaction between channels, repeat steps 2
and 3 until there is no further interaction.
GENERAL OPERATION
Either of the two channels of the Type 1A2 can be used
independently by setting the MODE switch to CH 1 or CH 2
and connecting the signal to be observed to the appropriate
input. Table 2-1 lists several input systems compatible with
the Type 1A2 input. Fig. 2-2 shows a block diagram of the
input when using the system outlined in Method 7 of Table
2-1. Figure 2-3 shows the X, and R curves for the Type 1A2.
Use of Probes
A conventional passive attenuator probe with a standard
42-inch cable lessens both capacitive and resistive loading,
but at the same time reduces sensitivity. The attenuation
introduced by the probe permits measurement of signal volt-
ages that would overscan the CRT if applied directly to the
Type 1A2. However, in applying high-amplitude signal volt-
ages to either the probe or Type 1A2, do not exceed their
maximum voltage ratings. When making amplitude meas-
urements with an attenuator probe, be sure to multiply the
observed amplitude by the probe attenuation factor.
To assure the accuracy of pulse or high-frequency measure-
ments, check the probe compensation. To make the adjust-
ment, proceed as follows:
1. Set the oscilloscope Amplitude Calibrator for a calibra-
tor output signal of suitable amplitude (at least 2 cm).
2. Place the MODE switch to the appropriate channel set-
ing (CH 1 or CH 2) to be used with the probe.
3. Touch the probe tip to the calibrator output connector
and adjust the oscilloscope controls to display several cycles
of the waveform.
4, Adjust the probe compensation for best square-wave
response as shown in the right-hand picture of Fig. 2-4.
NOTE
If a square-wave source other than the oscilloscope
calibrator is used for compensating the probe, do
not use a repetition rate higher than 5 kHz. At
higher repetition rates, the waveform amplitude
appears to change as the probe is compensated.
Thus, proper compensation is difficult. If the probe
remains improperly compensated, measurements
will be inaccurate.
2-3

Operating Instructions—Type 1A2
1M T
=S
N
100 k x
~
AN
~
N
N
N X
\ \,
N Xe
Ohms 10k x x
aN »
aN
. \
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1000
— eH
ww
N
N
N
100
:
1 MHz 10 MHz
Frequency in Megacycles Per Second
Fig. 2-3. Type 1A2 nominal input resistance and capacitive reactance vs frequency at any position of the VOLTS/CM switch.
AC-DC-GND Switch
To display both the DC and AC components of an applied
signal, set the AC-DC-GND switch to DC; to display only the
AC component of a signal, set the AC-DC-GND switch to AC.
In the AC position of the switch, the DC component of
the signal is blocked by a capacitor in the input circuit.
The input time constant of the input circuit is about 0.1
second and the low-frequency response of the unit is down 3
dB at about 2Hz. If a 10X attenuator probe is used with
the Type 1A2, the low-frequency response will be extended to
about 0.2 Hz with a 100X probe, low-frequency response ts
about 2 Hz.
Placing the AC-DC-GND switch to the GND position
grounds the input circuit of the Type 1A2 to provide a DC
2-4
zero reference. When the AC-DC-GND switch is set to GND,
the switch internally disconnects but does not ground the
applied signal at the input connector. The GND position of
the switch eliminates the need for externally grounding the
input of the unit or probe tip to establish the ground
reference.
VOLTS/CM Switch and VARIABLE Control
The amount of vertical deflection produced by a signal is
determined by the signal amplitude, the attenuation factor
{if any) of the probe, the setting of the VOLTS/CM switch
and the setting of the VARIABLE control. Calibrated deflec-
tion factors indicated by the settings of the VOLTS/CM switch
apply only when the VARIABLE control is set to the CALI-
BRATED position. Errors in display measurements may result