Tektronix 7A14 User manual

INSTRUCTION
MANUAL
Tek tr onix, Inc.
Seriol Nu mber ____ _
TYPE 7AJ~
CURRENT PROBE
AMPLIfIER
S.W . Millikan Way . P. O. Box 500 • Beoverlo n, Oregon 97005 • Phone 644 ·0 1 61 • Cab l es ! Tektronix
070 ·0 979 -00
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Type 7A14
TABLE OF CONTENTS
SECTION 1 SPECIFICATION
Introduction
Electrical Characteristics
Environmental Characteristics
Physical Characteristics
SECTION 2 OPERATING INSTRUCTIONS
General
Installation
Front Panel Controls and Connectors
First-Time Operation
General Operating Information
Measurement Techniques
SECTION 3 CIRCUIT DESCRIPTION
Introduction
Block Diagram
Input Connector
Input Attenuators
Input Amplifier
Low-Frequen'Cy Compensation
First Cascode Stage
Second Cascode Stage
Third Cascode Stage
Output Amplifier
Trigger Pickoff
Readout Block
SECTION 4 MAINTENANCE
®
Introduction
Preventive Maintenance
Troubleshooting
Introduction
Troubleshooting Aids
Troubleshooting Equipment
Troubleshooting Techniques
Corrective
Maintenance
Obtaining Replacement Parts
Soldering Techniques
Component Replacement
Recalibration After Repair
Page
1-1
1-1
1-1
1-1
2-1
2-1
2-1
2-1
2-3
2-5
3-1
3-1
3-1
3-1
3-1
3-2
3-2
3-3
3-3
3-4
3-4
3-4
4-1
4-1
4-1
4-1
4-2
4-2
4-4
4-5
4-5
4-5
4-6
4-7
SECTION 5 PERFORMANCE CHECKI
CALIBRATION
Introduction
Test Equipment Required
Short-Form Procedure
General
5-1
5-1
5-2
5-3
Preliminary Procedure for Complete Calibration 5-4
Adjust DC Balance 5-4
Adjust Internal Gain Ratio 5-5
Adjust 5 mA Gain 5-5
Adjust P6022 Current Probe Gain
Check/Adjust Front-Panel GAIN
Check Deflection Accuracy
Adjust High-Frequency Compensation
Check/Adjust Low-Frequency Compensation
Check VAR
CURRENT /DIV
Check Trigger Out Gain
Check Trace IDENTIFY
Check LF -3 dB Point
Check
20 MHz Bandwidth
Check HF -3 dB Point
Check
Overall Noise Level Tangentially
SECTION 6 ELECTRICAL PARTS LIST
Abbreviations and Symbols
Parts Ordering Information
Index of Electrical Parts. List
Electrical Parts List
5-5
5-5
5-6
5-7
5-8
5-9
5-9
5-9
5-9
5-10
5-10
5-12
SECTION 7 DIAGRAMS AND MECHANICAL
PARTS ILLUSTRATIONS
Diagrams
Mechanical Parts Illustrations
SECTION 8 MECHANICAL PARTS LIST
Mechanical Parts List Information
Index of Mechanical Parts Illustrations
Mechanical Parts List
Accessories
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7A14
POSITION
LF COMP
POLARITY
•• UP
• INVERT
BANDWIDTH
II FULL
.20MH •
.... _, ..
YA~'AIIU CA L IN
CURRENT/ DIV
CURRENT PROB! INPUT
- :URRENT PROBE AMPLIfiER
7A14
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®
ArtekMedia
Digitally signed by ArtekMedia
DN: cn=ArtekMedia, o=ArtekMedia.com,
ou, [email protected], c=US
Date: 2008.11.16 17:26:19 -06'00'

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Type 7A14
SECTION J
SPECIfICATION
Change information, if any, affecting this section will be found at the
rear of the manual.
Introduction
The Type 7A14 Current Amplifier vertical plug-in unit is
designed for use with Tektronix P6021 and P6022 Current
Probes or at reduced performance with P60191 and P6020
Current Probes. The Type 7A14
is part of a Tektronix 7000-
series Oscilloscope System. The Type 7A14 provides cali-
brated deflection factors from 1 mA/DIV to 1 A/DIV.
In-
ternal gain and compensation circuits are automatically
switched to correspond with the requirements of the current
probe being used, when the current probe is connected to
the amplifier
INPUT connector. A polarity switch permits
ELECTRICAL
Characteristics Performance
Deflection Factor 1 mA/Div to 1A/Div
in a 1-2-5
Calibrated Ranges sequence
Gain Ratio Accuracy Within 2% of GAIN adjusted
at
10 mA/div
Uncalibrated Variable between steps, extends
(Variable) deflection factor to
at least 2.5A/
div
Gain Range
GAIN (front-panel) Permits adjustment of deflection
factor
at 10 mAldiv for all indi-
cator oscilloscopes
Frequency Response
Upper
-3 dB Band- With P6021 With P6022
width (system de-
pendent)
7500-series Indicator 45 megahertz 75 megahertz
Oscilloscope
7700-series Indicator 50 megahertz 105 megahertz
Oscilloscope
Lower -3 dB Band- 30 hertz
or 250 hertz or less
width less, 00 to
+200i C 25
hertz
or less,
+20
0 C to
+75
0 C
Noise (tangentially 0.2 div
or less (square wave val-
measured)
ue) throughout calibrated deflec-
tion factor
range when amplifier
is operated in a 7000-series oscill-
oscope.
Maximum
CW Current
With P6021
15 A P-P to 5 MHz decreasing to
1 A
P-P at 100 MHz
With P6022 6 A
P-P to 10 MHz decreasing to
2 A
P-P at 150 MHz
inversion of the input current signal within the amplifier.
A bandwidth limiting switch allows low-frequency, low-level
signals to be viewed with reduced interference from signals
above 20 megahertz.
The electrical characteristics described
in this section are
valid over the stated environmental range for instruments
calibrated
at an ambient temperature of +20
0 C to
+30
0 C
and after a five minute warmup unless otherwise noted.
'A special coding ring is required when using the P6019 Current
Probe.
Characteristics Performance
Maximum Pulse Current
With P6021 25 A Peak, not to exceed an amp-
second product of 2 A-msi not to
exceed 5.3
Arms
With P6022 25 A Peak, not to exceed
an amp-
second product of 30
A-P.Si not to
exceed
2.1 Arms
Maximum Voltage
With
P6021 or P6022 600 V
(DC + Peak AC)
DC Saturation
With
P6021
0.5 A
With P6022
0.2A
Insertion Impedance
With P6021
0.03 n or less at 1 MHz, increasing
to 1 n
or less at 60 MHz
With P6022 0.03 n or less at 1 MHz, increasing
to 0.7 n
or less at 175 MHz
ENVIRONMENTAL
Altitude
Non-operati
ng
Transportation
Finish
Dimensions
Weight
To 50,000 feet and _55
0 C
Qualified under National Safe
Transit Committee test procedure
1
A, Category II
PHYSICAL
Front panel is anodized aluminum
141f4 inches Lx 2% inches W x 5
inches H overall
:::::1% Ibs
1-1

NOTES
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Type 7A14
SECTION 2
OPERATING INSTRUCTIONS
Change information, if any, affecting this section will be found at the
rear of the manual.
General
The Type 7A14 vertical plug-in unit operates with a Tek-
tronix 7000-series indicator oscilloscope, a 7B-series time
base unit, and Tektronix P6021 or P6022 Current Probes to
form a complete current measuring system. To effectively
use the Type 7A14, the operation
and capabilities of the
instrument should
be known. This section describes the op-
eration of the front-panel controls, gives first-time operation
and general operating information, and lists some measure-
ment techniques using the current probes.
Installation
The Type 7A14 is designed to operate in a vertical plug-
in compartment of Tektronix 7000-series oscilloscopes. For
X-Y operation, the plug-in unit may also be installed in a
horizontal plug-in compartment. (Refer to the indicator os-
cilloscope instruction manual for information concerning
X-Y
operation.)
To install the Type 7A14 into a plug-in compartment, push
it in until it is seated against the front panel of the indicator
oscilloscope.
To remove, pull the release latch to disengage
the plug-in unit from the indicator oscilloscope. Continue to
pull the release latch to remove the unit from the oscilloscope.
FRONT-PANEL CONTROLS AND CONNECTORS
All controls and the connector required for operation of
the Type 7A14
are located on the front panel of the unit (see
Fig. 2-1). A brief description of the function or operation of
the front-panel controls
and the connector follows. More
detailed information
is given under General Operating
Information.
CURRENT IDIV Selects vertical deflection factor from 1
mAIDiv to 1 AMP/DIV in 1-2-5 sequence
(VAR control must be in the calibrated
position for indicated deflection factor).
VAR (CAL IN)
POSITION
IDENTIFY
POLARITY
Provides variable uncalibrated deflection
factors to
at least 2.5 times the setting of
the
CURRENT IDIV switch. Push knob in
and release to activate; the knob moves
outward from the
CURRENT IDIV control
when activated.
Controls vertical position of trace.
Moves trace upward
about 0.25 divisions
for identification. Also identifies the read-
out corresponding to the Type 7A14.
Provides means of inverting the display.
BANDWIDTH
LF COMP
GAIN
NORM:
INVERT:
Conventional current flowing
in the direction of the arrow
on the probe (see Fig. 2-2) pro-
duces a positive deflection
on
the CRT.
Conventional current flowing
in the direction of the arrow
on the
probe produces a neg-
ative deflection on the
CRT.
Provides limiting of upper bandwidth.
FULL:
20 MHz:
Normal operation with
full
bandwidth capabilities.
Amplifier bandwidth limited
to 20 MHz to provide a re-
duction in displayed high-fre-
quency noise
or interference.
Screwdriver adjustment to compensate low-
frequency response.
Screwdriver adjustment to set the gain of
the amplifier. The 10
mA position is color
shaded to indicate that the GAIN should
be adjusted in this position of the switch.
CURRENT PROBE Signal input connector. Similar to standard
INPUT BNC connector, but with additional con-
ductor.
When the P6021 probe is con-
nected to the input, the additional con-
ductor
is shorted to ground by the probe
connector, actuating relays
in the Type
7A14 to set the gain
and peaking circuits
to correspond with the
P6021 probe.
NOTE
P6021 probes with regular BNC connector must be
modified with a special coding ring to be compat-
ible with the 7 -series plug-in units. Contact your
local Tektronix Field Office or Representative for
assistance in procuring the coding ring.
FIRST-TIME OPERATION
General
When shipped from the factory, the Type 7A14 has been
calibrated to meet the specifications listed
in Section 1 and
is ready to be used with an indicator oscilloscope.
The following steps demonstrate the basic operation of
the controls
and connectors of the Type 7A14. It is recom-
mended
that this procedure be followed completely for
familiarization with the instrument.
Operation of the indi-
cator oscilloscope and time base unit is described in the
instruction manuals for those units.
2-1

Operating Instructions-Type 7A14
.""",
POSmoN
LF COMP
POLARITY
•
+UP
•
INVERT
~DW1DTtI
•
FUU
•
20MHz
~.
A
VARIABLE l CALIN
CURRENT/OIY
CURRENT PROBE INPlIT
7A14 CURRENT PROBE AMPUFIER
Fig. 2- 1. Loco'ion of "onl-pon el ~onl , oh and cU"e nt prob e conneclor .
2-2
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Fig. 2-2. Curre nt flow I.. a co nd uctor.
Setup Information
1. Insert the Type 7A14 into Q vertical plug,in comportment
of 0 7000-series indicator oscilloscope.
2. Insert 0 7B-series time-bose unit inlo 0 horizontal plug-
in comportment.
3. Sel the controls as follows:
Type 7AI4
CURRENT IDIV lOrnA
VA'
Calibrated
(CAL IN)
POSITION Midrange
BANDWIDTH
FULL
Time Bose
Time/Div
0.5 msee
Variable TimelDiv Calibrated
MODE
p.p AUTO
Slope +
Coupling
AC
Source
,,'
Position
Midrange
Indicotor Oscilloscope
Cali brator
1 kHz
Intensily Counterclockwise
Focus Midrange
Astigmatism Midrange
Scale Ilium
As desired
4. Connect the oscilloscope to 0 power source which meets
the voltage and frequency requirements of the oscilloscope
power supply.
5. Turn the oscillosc ope power on and allow about five
minutes
warmup time.
6. Connect either a Tektronix P6021 or P6022 Current Probe
to the INPUT connector.
7. Open the probe slider, pl ace the probe around the
oscilloscope calibrator 40 mA current loop and lock the
slider.
Op e rating Instructions.----Type 7A14
Fig. 2-3 . 40 mA Calibrator . quor . -wa .. . .
8. Turn the Intensity control clockwise and adjust trig-
gering controls to obtain a tr iggered display. (Adiust hori-
lontal and vertical POSITION controls as necessary.)
9. Adjust Focus
and Astigmatism controls for on optimum
display of the square wove.
10 . Check the display for four divisions of vertical deflec-
tion (see
Fig . 2·3).
II. Press the
IDENTIFY button to identify the readout. The
Type 7A14
readout wi ll be replaced by the word "I DENTIFY".
When the IDENTIFY bullon is pressed and released, the dis-
play moves up and down about 0.25 division. This movement
identifies the Type 7A 14 waveform when more than one dis-
play
is on the CRT .
12. Press the
INVERT button to display the opposite polarity
of the
square wove . (When observing a symmetrical wave-
form, such as the calibrator square wave, inverting the vertical
signal makes no
apparent change in the display. This is due
to the time- bose unit triggering on the indicated slope of the
displayed wa veform.)
This completes the basic
operating procedure for the Type
7A14. Instrument operations not explained here, or operations
which need further explanation,
are discussed under General
Operoting Information.
GENERAL OPERATING INFORMATION
Current Probe Selection
The two current probes recommended for use with the Type
7A14 are the Tektronix P6021 and P6022. Generally , the
P6021 shou ld be used when measuring current waveforms in
the low
to medium·frequency range, while the P6022 should
be used for medium or high-frequency measurements. The
P6022 is con si derably smaller in sile than the P6021.
The P6021 ond P6022 probes require different gain and
peaking in the amp li fier to provide on accurate represen-
tation of the CUffent signal. To accomplish these changes
automatically, a speci al BNC connector with a third con-
ductor is used for the INPUT. When the P6021 is connected
2-3
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Opera ting Instruc ti ons---Type 7A14
to the INPU T, this additional conductor is shorted to ground,
relay-switching the necessory internal circuits to correspond
with the probe being used. No contact
is mode to this con-
ductor by the P6022 probe connector.
Signal Connection
The current signal is connected to the amplifier by sliding
the thumb-controlled portion 01 the probe bock, placing the
probe around the current-carrying conductor, and moving the
slider forward, closing the probe transformer core around the
conductor.
Signal Polarity
Conventional current (plus to minus) flowing in the direction
of the arrow on the probe produces a positive deflection on
the
CRT when the POLARITY switch + UP button is pressed.
When the
INVERT button is pressed, conventional current
flowing
in the direction of the arrow produces a negative
dellection an the CRT .
Deflection Factor
The amount of vertical deflection produced by a signal is
determined by the signal amplitude, the setting of the CUR-
RENT/DIV switch, and the setting of the VAR CURRENT / DIV
control. The calibrated deflection factors indicated by the
CURRENT/D IV switch apply only when the VAR control is
in the calibrated (pushed in) position.
The
VAR CURRENT/DIV control provides uncalibrated
vertical deflection factors between the settings of the
CUR-
RENT/DIV switch. The VAR control extends the maximum
vertical deflection,factor of the Type 7A14 to at least 2.5
amperes/division with the
CURENT/D IV switch at 1 A/Div.
Bandwidth Limit er
The bandwidth switch provides a method of reducing in-
terference from unwonted high-frequency signals when view-
in g low-frequency signals. With the fULL bullon pressed,
the
full bandwidth capabilities of the amplifier are available.
When the 20 MHz bullon is pressed, the upper -3 dB band-
width point of the amplifier is limited to about twenty mega-
hertz. The unwanted high-frequency signals (such as tel e-
vision broadcast radiation interference) are reduced in the
displayed waveform.
Fig. 2-4 illustrates the use of this fea·
ture. The waveform in Fig . 2-4A is the display produced
when a low-level, low-frequency signal
is viewed in the pres-
ence of a strong SO-megahertz radiation (FULL bulton pres-
sed). Fig. 2-4B shows the resultant CRT display when the high.
frequency interference
is reduced by pressing the 20 mega-
hertz button.
Low-Frequency Compensation
The low-frequency response of the probe and amplifier
varies when changing fr
om one probe to another, even
among probes of the some type. Therefore, a low-frequency
compensation adjustment
is provided on the front panel to
match the amplifier response to the response of the probe
being used.
To compensate the amplifier, proce(!d as follows:
1. Connect the P602! probe from the Type 7A14. to the
indicator oscilloscope
40 rnA current loop and set the cali-
brator rate to 1 kHz. Set the TIME/DIV to .2 ms.
2-4
F la . 2-4. (A I C RT dI s pl ay showl..g hlgh-' .. q ... . n'Y In l. rI ." ..c. wh. n
att.mp tl..g to yl. w 1 0w-l.y. l, !o w- lr.q u, ..'Y , Ig not, IBI "su ltant dis_
play whe.. the 20 MH
~ bullon I, p .. ,,, d.
2. Set the CURRENT/DIV to lOrnA and the VA R to the
CAL IN position. Adjust the triggering controls for a stable
display.
3. Adjust the LF CaMP (a front-panel adjust) for 0.2 div i-
sion of tilt in the first 500 p.s of the square-wave. See F ig .
2-5A.
4. Reset the CURRENT/DIV to 5mA and adjust LF COMP
for 0.4 division of lilt in the first 500 }J-S. See Fig . 2-56.
5. Replace the P6021 probe with the P6022 probe. Reset
the CURRENT /DIV to 10 rnA and the TlME/ D IV to .5 ms.
6. Adjust LF COMP for best flat top on waveform (see
Fig .2- 5C) .
7. Reset the CUREN T/DIV to 5 rnA and adjust LF COMP for
best flat top.
NO TE
T he a ppr op r iate steps in the above proced ure
should be checked e ach time wh en ch anging
probes.
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