Tektronix AM 502 User manual

Tektronii. Inc
P.O Box SOO
Beaverton. Oregon
l^ktronix-
COMMTTTED TO E)CELLENCE
AM 502
DIFFERENTIAL
AMPLIFIER
INSTRUCTION MANUAL
97077 Serial Number
070-1582.01
PtodjCi Group 75 First Printing MAY i983
Revised OCT i966

Copyright *1973. 1976 TeKtronix. Ir>c All rights m*rveO
Cont«r>it of this publication may rwt be reproduced in any
form without the written permission o< TMIronix, Inc
Products Of Tektronix. Inc and iissubsidiaries are covered
by USand foreign patents and/or pending patents
TEKTRONIX TEK SCOPE-MOeiLE. and
isiered trademarxs ot Tektronix, Inc are reg-
Printed in uSASpecification and price change privileges
are reserved
INSTRUMENT SERIAL NUMBERS
Each instrument has aserial number on apanel insert, tag.
or stamped on the chassis. The first number or letter
designates the country of manufacture. The last five digits
of the serial number are assigned sequentially and are
unique to each instrument. Those manufactured in the
United States have six unique digits. The country of
manufacture is identified as follows:
BOOOOOO Tektronix. Inc.. Beaverton, Oregon. USA
100000 Tektronix Guernsey. Ltd., Channel Islands
200000 Tektronix United Kingdom. Ltd., London
300000 Sony/Tektronix. Japan
700000 Tektronix Holland. NV. Heerenveen.
The Netherlands

AM 502
TABLE OF CONTENTS
Pag«
Saction 1OperaUng Inatructlona 1-1
ENGLISH VERSION
FRENCH VERSION
GERMAN VERSION
JAPANESE VERSION
Saction 2SPEaFICATIONANDPERFORMANCE
CHECK 2-1
WARNING
THE FOLLOWING SERVICING INSTRUCTIONS
ARE FOR USE BY QUALIFIED PERSONNEL ONLY.
TO AVOID PERSONAL INJURY. DO NOT
PERFORM ANY SERVICING OTHER THAN THAT
CONTAINED IN OPERATING INSTRUCTIONS
UNLESS YOU ARE QUAUFIED TO DO SO.
Section 3ADJUSTMENT 3-1
Page
Section 4MAINTENANCE AND INTERFACING
INFORMATION 4-1
Section 5CIRCUIT DESCRIPTION 5-1
Section $OPTIONS 6-1
Section 7REPLACEABLE ELECTRICAL PARTS 7-1
Section 8DIAGRAM AND CIRCUIT BOARD
ILLUSTRATION 8-1
Section 9REPLACEABLE MECHANICAL PARTS
AND EXPLODED VIEW 9-1
CHANGE INFORMATION
REV CSEP 1980 I

AM 502
isa2i
AM 502 Oiftervntlal Amplifier plug>in module.
ii REV CSEP 1960

Section 1—AM 502
OPERATING
INSTRUCTIONS
INTRODUCTION
Description
The AM 502 i$ adc-couple<j differential amplifier with
excellent common-mode rejection capabilities and high
gain for low voltage measurements. The dc offset capabili-
ty permits nulling up to 1volt dc, so that low level, low
frequency signals impressed on adc level can be
amplified without the degradation often introduced byac
Input coupling. High and low frequency -3d6 points can
be selected at the front panel to suit the application. Signal
inputs and outputs are available at the rear connector as
well as at the front panel. Afront panel lamp indicates
most overrange conditions of excessive input signal,
excessive gain, or excessive offset.
The input circuit can be represented by approximately
1megohm to ground paralleled by approximately 47
picofarads. The Input impedance can be raised to about
200 megohms with the removal of ajumper.
Overload protection is provided by fuses In series with
the input which open when largeamountsof current flow
due to overloading conditions.
ASTEP GAIN DC BALANCE control iS provided to
adjust for zero shift as the gain switch is changed from one
position to another.
The DC OFFSET COARSE and FINE controls give
offset up to ±1 volt dc potential difference at the input
connectors. The amplifier internal bias is changed to
accomplish the offset. The LF -3 dB switch must be In the
DC OFFSET position to actuate these controls.
The HF -3 dB switch is used to reduce the upper
bandwidth limit as necessary to improve the signal-to-
noise ratio when using the AM 502 in low-frequency
applications. The LF -3 dB control increases the lower
bandwidth frequency.
Use of the pre-charging feature prevents surge
currents, due to charging the ac coupling capacitor, from
damaging the circuit under test.
Installation and Removal
Turn lh» powermodule offbefore inserting the plug-
in: otherwise, damage may occur to the plug-in
circuitry. Because of the high current drawn by the
AM 502, it is also recommended that the power
module be forned off before removing the AM 502.
Refer to Fig. 1-1. Check to see that the plastic
barriers on the interconnecting jack of the selected
power module compartment match the cut-outs in
the AM 502 circuit board edge connector.
Align the AM 502 chassis with the upper and lower
guides of the selected compartment. Push the module in
and press firmly to seat the circuit board in the inter-
connecting jack.
To remove the AM 502. pull on the release latch located
in the lower left comer, until the interconnecting jack
disengages and the AM 502 will slide out.
Controls and Connectors
Refer to Fig. 1-2. Even though the AM 502 is fully
calibrated and ready to use. the functions and actions of
the controls and connectors should be reviewed before
attempting to use it. Pull the Power switch on the power
module to apply power to the AM 502. The POWER
indicator light indicates when power is applied to theAM
502
OPERATING CONSIDERATIONS
Overheating
The AM 502 is designed to operate at an ambient
temperature from 0” to -^-SO^C. However, when operating
several power supplies In amulti-plug-in power module,
especially at low output voltages, or when operating close
to other heat-producing equipment, internal temperature
may exceed safe limitsandactuatea thermal cutout in the
power module. Refer to the power module instruction
manual for more complete information.
REV DSEP 1980 M

Operating Instructions
—
AM S02
Fig. t*l. Pkjg-in Installation and removal.
Input Connections
Unshielded test leads can be used to connect the AM
502 to asignal source when ahigh-level, low-frequency
signal is monitored at alow impedance point. However,
when any of these factors is missing, it becomes in-
creasingly important to use shielded signal cables. In all
cases, the signal-transporting leads should be kept as
short as practical.
When making single-ended input measurements
(conventional amplifier operation), be sure to establish a
common ground connection between the device under
test and the AM 502. The shield of acoaxial cable is
normally used for this pun>ose. See Fig. 1-3 for reference.
Push the GND button for the input not connected to the
device under test.
In some cases differential measurements require no
common chassis ground connection, and therefore are
less susceptible to interference by ground-loop currents.
Probes
Attenuator probes decrease the resistive-capacitive
loading of asignal source. They also extend the measure-
ment range of the AM 502 to substantially higher voltages.
Some measurements require ahigher resistance input to
the AM 502. with very little source loading or signal
attenuation. In such situations use aFET probe or the
high-impedance input provision ot the AM 502. Contact
your Tektronix Representative for further Information on
probes.
High Impedance Input
To raise the internal input impedance of the AM 502 to
about 200 megohms, remove the P40plug (Fig. 3-1 ]. Make
certain the attenuator is in the NORM mode. Signal source
impedance now becomes an important factor. For exam-
ple, atoo picoampere gate current through 10 megohms
produces aone-mllllvolt offset. This offset may result in
significant error when small voltages are measured.
Consider the change in the source operating
characteristics due to loading by the signal input cables.
The circuit at the input connectors can be represented by
approximately 1megohm to ground paralleled by ap-
proximately 47 picofarads Two feet of 50 ohm coaxial
cable increases the parallel capacitance by about 60
picofarads, which could be excessive in many situations.
To minimize these effects, use ahigher impedance cable
or an attenuator probe.
input Overloading
When measuring unknown dc voltages, push the -^100
pushbutton in, and start with the 100 position on the GAIN
switch. Increase the GAIN switch setting and finally
release the -rt 00 pushbutton until asuitable output signal
IS obtained. If the input circuit of the AM 502 is overdriven,
large amounts of current will flow, opening the protective
fuses.
1-2 REV CSEP 1980

operating Instructions—AM 502
STEP GAIN DC BAL Control
Adiusts dc balance In the
preampliller stage.
Variable Gain Control con-
tinuously variable.
Calibrated in thecw position.
GAIN Switch
Selects amplifier gain.
OVER RANGE Indicator
When lit, indicates most over-
range conditions.
+100 Pushbutton
Divides GAIN switch setting
by 100.
snaaMB
OC UL
DCOfTSFTSn
naf -*-a!»sv
OC OFFSET COURSE and FINE
Controls
fProvides Intental olfset ol
approximately ±1 Vto input
signal. LF —3 dB switch must
be In the OC OFFSET position
for controb to operate.
POWER Indicator
When lit. Indicates power Is
applied.
AC Pushbutton
Selecb the input signal (ac or
dc) into the negaUve side ol the
preamplifier.
4- Inpul Conrtector
6NC connector tor the
positive side of the amplifier.
GND Pushbutton "
Grounds Tamplifler input
Ground Binding Post
Provides achassb return for
signab.
naaKCSsn
pvaetstMwu.
Obf>-*£
Kjpg]
Ibsl
wf- r*c
n-*U
UUS -
V
Cf-3d8
LtfVTCDSf
•mcomm
OUTTUT
:sv MiMUAX
HF -3dB Switch
Selecb upper -3dB point of
the amplifier.
LF -3 dB Switch
'Selecb lower —3 dB point of
the amplifier and activates DC
OFFSET controls.
OUTPUT Connector
BNC output terminal con-
nector.
-Input Connector /
BNC connector for the
negativa side ol the amplifier.
onus AM 502f DIFFERENTIAL AWPL AC Pushbutton
Selecb the inpul signal (ac or
dc) into the positive side ol the
preampllfbr.
Release Latch
Pull to remove plug-ln.
GND Pushbutton
Ground -amptitier inpuL
REV CSEP 1980 1-3

Operating Inatructions—AM 502
Fig. 1-3. Waveformeahowlrtg dltferenttsttejeclion ofacofnmen-fliodeiJgnal.ReMltanlweMtormchowttiedillerence between
ttie two tignalt.
Step Gain DC Balance
Output Connections Kcontrol is misadjusled, the dc output level will
Make output connections using abnc to dual binding shitt as the GAIN switch position is changed. Push both
post connector, or acoaxial cable with at least one bnc GNO buttons and place the GAIN switch in the 100
connector. To prevent current limiting in the outputstage. position. Rotate the GAIN switch from stop to stop while
do not load the output with less than 250 ohms. Output adjusting the STEP GAIN DC BAL control for node shitt at
current is limited to 20 milliamperes. the OUTPUT terminal.
1-4 REV CSEP 1980

operating Instructions—AM 502
DC Offset Coarse and Fine
Use these corjtrols to offset up to =1 volt dc potential
difference at the input connectors. The amplifier internal
bias Is changed to accomplish the offset. The differential
rejection capabilities of the AM 502 are not affected. The
LF -3dB switch must be in the DC OFFSET position to
activate these controls.
HF and LF Bandwidth Reduction
Use the HF -3dB switch to reduce the upper bandwidth
limit, as necessary, to improve the signal-to-noise ratio
when using the AM 502 in low-frequency applications.
The LF -3dS control increases the lower bandwidth
frequency. Use this control to reduce dc drift, when
raising the lower bandwidth does not undesirably reduce
the bandwidth for the signal being measured.
Pre-Charging
Use of this feature prevents surge currents, due to
charging the ac coupling capacitor in the AM 502. from
damaging the circuit under test. Before conrtecting the
AM 502 to asignal containing adc component, push the
AC and GND pushbuttons. Conrwct the input to the circuit
under test. Wait about one second for the coupling
capacitor to charge. Release the GND pushbutton, and
the coupling capacitor Is charged to the value of the dc
voltage to be measured.
Differential Operation
Adifferential measurement is made by connecting
each of the two inputs to selected points in the test circuit.
The Input to the amplifier will then be the difference in
voltage of the two selected points. Consideration should
be given to the proper connection method used between
the AM 502 and the circuit under test: otherwise improper
measurement results may occur. See Fig. 1-4 for
reference.
Differential voltage measurements are made by apply-
ing the signals to the +input and -input connectors. Set
the input coupling switches to the same position, AC or
DC, depending on the measurement being made, in
differential measurements, only the voltage difference
between the two signals is amplified. Common mode
signals (common in amplitude, phase, and frequency) are
rejected. See Fig. 1-3 A, B, and Cfor reference.
(A) Rlehl
(B) Wrong
(C) Wrong
undor lest net bo grounded to
oquipmont under teet log3i)isS2
Single-ended measurements often yield unsatisfactory Fig. i-4. Connecting adltterentlel emplliler to •signal source,
results because of the interference resulting from ground-
loop currents between the AM 502 and the device under capacitor, which could limit the low-lrequency response
test. In other cases, It may be desirable to eliminate adc The limitations of single-ended measurements are effec
voltage by means other than the use of ablocking tively eliminated by using differential measurements.
REV CSEP 1980 1-5

Operating Instructions—AM 502
DQ Offset Operation
By using the FINE and COARSE DC OFFSET controls,
it Is possible to use the AM 502 differentially in aslide-back
mode, to observe asmall signal whose dc potential
difference may be considerable. The offset voltage is
continuously adjustable from plus 1volt to minus 1volt,
and Is internally available for all of the GAIN switch
positions. The LF -3dB switch must be in the DC OFFSET
position to activate the offset circuit.
Common Mode Rejection Ratio
The ability of the AM 502 to reject common-mode
signals Is Indicated by the common-mode rejection ratio
(cmrr). For example, assume that asignal consists of
unwanted 60 hertz at 10 volts peak-to-peak (common
mode connected to both inputs), plus adesired signal at 1
millivolt peak-to-peak (differentially connected to one
input). The AM 502 gain is setat200.TheoutputoftheAM
502 shows the desired signal at an amplitude of 0.2 volt (1
millivolt X200), and the 60 hertz signal is viewed at an
amplitude of 0.02 volts. The cmrr in this application is
100,000 to 1. This figure is calculated by multiplying the
value of the common-mode signal (10 volt) by the gain of
the amplifier (200) for aproduct of 2000 volts. This product
is divided by the observed 60 hertz voltage at the output
(0.02 volt] and result is the cmrr. 100.000 to 1. It would, of
course be impossible to view the 1millivolt signal
superimposed on the 60 hertz signal by using single input
methods.
Degradation of Common Mode Rejection
There are a number of factors that degrade common-
mode rejection ratio (cmrr). The principal requirement for
maximum rejection is for the common-mode signal to
arrive at the input FET gates at the same phase and
amplitude. Adifference of only 0.01% in the attenuation
ratios of the input attenuators will reduce the rejection
ratio to 10,000 to 1. Also, any difference in source
impedance will degrade the rejection ratio. Figures 1-5
and 1-6 show common-mode rejection degradation due to
differences in source impedance. The frequency of the
common-mode signal also affects the common-mode
rejection ratio. Generally, as the frequency of the input
signal increases, the common-mode rejection ratio is
more difficult to maintain.
Fig. 1-5. Relallonthip ol twt point wure* Impodanee to the
amplifior Input Impodanca end thaapparenl CMRR caused by (A)
large dlttaranca batwcon lasl-point Impedancas and (B) low
knpadanca Mat points.
1-6 REV 0SEP 1980

Operating Instructions—AM 502
Fig. 14. Simplified Input circuit and table thawing the change In
apparent CMRR due lo 10X probe* thatar*wlthlnl,2, and3%el
their attenuation value* (with matched 1megohm realatort).
The high frequency cmrr will also depend upon the
signal source impedance, since various shunt
capacitances between the source and the input gate must
charge and discharge through that impedance.
Outside influences such as magnetic fields can also
degrade the performance, particularly when low level
signals are involved. Magnetic interference maybe reduc-
ed by using identical signal transporting leads to the two
inputs. Twist the two leads together over as much of their
length as possible. Low-frequency measurements can be
similarly protected by using a shielded cable that contains
atwisted pair of conductors.
REVASEP19S0 1-7

Section 2—AM 502
SPECIFICATION AND
PERFORMANCE CHECK
SPECIFICATION
Perlormance Conditions
The electrical characteristics are valid only if the AM
502 has been calibrated at an ambient temperature
between -i-20^ Cand -f-SO^C and Is operating at an ambient
temperature between 0”C and -i-50''C unless otherwise
noted.
Items listed in the Performance Requirements column
of the Electrical Characteristics are verified by completing
the Performance Check in this manual. Items listed in the
Supplemental Information column are not verified in this
manual: they are either explanatory notes or performance
characteristics for which no limits are specified.
Table 2-1
ELECTRICAL CHARACTERISTICS
Characteristics Perfonnance Requirements Supplemental Information
Gain
Normal Mode too to 100,000 within 2%.
10 steps in 1. 2. 5sequence.
-i-100 Mode 1to 1000 within 2%.
Variable Range Continuously variable uncal-
Ibrated gain to at least 2.5 times
the calibrated gain setting.
Frequency Response
Direct Coupled dc to 1MHz With Gain control set to 20K
or less, selectable HF -3dB
points are within +ldB. -2dB.
Upper -3dB point reduces to
500 KHz at 50K gain, and
250 KHz at 100K gain.
AC Coupled 2Hz or less, at lower
frequency -3dB point to lMHz.
Bandwidth
HF -3dB 100 Hz to 1MHz, 9 steps in
1-3 sequence. Reference approximately 5.0 V
peak-to-peak output at 1KHz.
Accuracy •^IdB. -2dB Reading range -2dB to -5dB.
LF -3dB 0.1 Hz to 10 kHz 6steps in
1-10 sequence
Accuracy +1dB. -2dB Reading range -2dB to —5dB.
REV. BMAR 1978 2-1

Specification and Performance Check—AM 502
Table 2-1 (Con'l)
Characteristics PerformarKe Requirements Supplemental Information
Output
Voltage Swing ±5 V.
I
i
Current
1
±20 mA
R« 5Qor less
Minimum Load
Impedance 250 0
Common Mode
Normal Mode
Range 1, ±5V,
Rejection Range ,100 dB. dc to SO kHz. Direct coupled with inputs
shorted together.
•1-100 Mode
Range *50 V,
Rejection Range
1
50 dB. dc to 50 kHz. Direct coupled with less than
1100 Vpeak-peak sine-wave input.
1
DC Offset
flange
f
At least -1- and -1V.
1
Maximum Safe Input
Voltage
Direct Coupled ^
Normal Mode IS V(dc plus peak ac) to
5MHz or less.
-i-IOOMode 350 V(dc plus peak ac) to
5MHz or less.
AC Coupled i350 V(dc plus peak ac) with
coupling capacitor precharged
Maximum Input Gate
Current (each input) 50 pA at 25*C.
Noise (Referred to
Input)
NORM mode <25 pV, tangentially
measured with 25 0
or less source resistance.
10 Hz to 1MHz selected
bandwidth. Typically
<6.0 nV/\/Hz above 1kHz.
-MOO Mode 1
1
1
j
I
I
I
I
Typically <2.0/iV/>/Hz
from 1kHz to 9kHz.
decreasing in al/F
fashion to <600 nV/\/Hz
1above 30 kHz.
Voltage Drift with i
Time 1
Short Term 10*/V (peak-to-peak) per hour
2-2 REV CSEP 1980

specification and Performance Check—AM 502
Table 2-1 (cont)
Characteristics
I
Ptflomianc* RequktniefiU Supplemental Information
Long Term 20 ^V (peak-to-peak) per hour.
Voltage Drift with
Temperature
100 pVper*C.
Input Rand CResistance. 1MO.
Capacitance. Approximately 47 pF.
Table 2-2
ENVIRONMENTAL
Characteristics Information
Temperature
Operating 0“Cto +50*0
Storage -40’ Cto +75* C
Altitude To 15.000 feet: maximun
Operating operating temperature
decreased by 1®C/1000
feet from 5000 to 15.000 feet.
Storage To 50.000 feet.
Vibration 'With the instalment complete
Operating and
Non-operating
1
1
1
and operating, vibration freq-
uency swept from 10 to 55 to
10 Hz at 1minute per sweep
Vibrate 15 minutes in each of
the three major axes at 0.015
inch total displacement. Hold
10 minutes at any major reson-
anace. or in none, at 55 Hz.
Total time 75 minutes.
Shock 30 g's 1/2 sine. 11 ms duration.
Operating and
Non-operating
2shocks in each direction along
3major axes, for atotal of 18
'shocks.
Table 2-3
PHYSICAL CHARACTERISTICS
Charactcrtsttcs Information
Overall Dimensions (measured at maximum points)
Height 5.0 inches
12.7 centimeter
Width 2.5 inches
6.35 centimeter
Length 11.8 inches
130.0 centimeter
Net Weight (Instrument Only) 1.8 lbs.
.82 kilograms
REV CSEP 1980 2-3

Sp«ci(ic«tion and Pariormance Check—AM 502
PERFORMANCE CHECK
Introduction
This procedure checks the electrical characteristics of
the AM 502 that appear in the Specification section of this
manual- If the instrument fails to meet the requirements
given in this performance check, the calibration
procedure should be performed. This procedure can also
be used by an incoming inspection faciiity to determine
acceptability of performance.
The electrical characteristics in Section 2 are valid only
If the AM 502 is calibrated at an ambient temperature of
+20* Cto +30* Cand operated at an ambient temperature
of 0*C to +50°C. Forced air circulation is required for
ambient temperature above +40*C.
Tolerances that are specified in this performance check
procedure apply to the instrument under test and do not
include test equipment error.
Test Equipment Required
The following test equipment, orequivalent, is required
to perform the performance check. Test equipment
characteristics listed are the minimum required to verify
the performance of the equipment under test. Substitute
equipment must meet or exceed the stated requirements.
Ail lest equipment is assumed to be operating within
tolerances.
Special test devices are used where necessary to
facilitate the procedure. Most of these are available from
Tektronix. Inc. and can be ordered through your local
Tektronix Field Office or representative.
Tabfe 2-«
LIST OF TEST EQUIPMENT REQUIREMENTS
Performance
Description Requirements AppHcatlona
1
Example
Oscilloscope Bandwidth, dc to 2MHz;
Minimum deflection
factor. 20 mV/div;
sweep rate. .2 ms/div
to 1/rs/div; accuracy,
within 3%.
Used throughout pro-
cedure to provide
display.
TEKTRONIX 5110.
SA13N. 5B10N.
Power Module Three compartments or
more.
All tests iTEKTRONIX TM 503 or
TM 504.
Calibration Gen-
erator
Amplitude calibration,
I
5mV to 10 V; accuracy.
±0.25% into 1MO: out-
put. square wave at
approximately 1kHz.
Amplifier gain check
1
TEKTRONIX PG 506
Calibration Generator.*
I
Function Generator Waveforms, sine and
square; voltage ampl-
itude. 10 Vp-p; freq-
uency range. 1kHz to
50 kHz: accuracy, with-
in 3%.
Signal generation
for cross neutral-
^ization and high
frequency cmrr
check.
TEKTRONIX FG 501
Function Generator.*
1
1
1
Termination Impedance, SO 0: accur-
acy. within 2%: conn-
ectors. bnc.
Output termination
for signal gen-
erator.
Tektronix Part No.
011-0049^1
Attenuator. 10X
(4 required)
Impedance. 50 Ci: accura-
cy. within 2%; conn-
ectors. bnc.
Output attenuation
for signal gen-
erator. Noise check.
Tektronix Part No.
'011-0059-02
Coaxial cable
(2 required)
Impedance. 50 Q: length.
:36 inches: connectors,
bnc.
^Provides signal
1interconnection.
1Tektronix Part No
;012-0057-01
*Requires TM 500-Serles power module
2-4 REV. BMAR 1978

Specification and Performance Check—AM 502
Preliminary Procedure
1.Ensure that all test equipment and the AM502 under
test are suitably adapted to the line voltage to be applied.
Refer to the installation section of the power module
manual.
2.
Ensure that all test equipment is suitably adapted to
the applied line voltage.
3.
Install the AM 502 into the power module, and if
applicable, install the TM 500 series test equipment into
the test equipment power module.
Time Base Plug-In
Time/Div
Variable
Triggering
+Slope
.5 ms
(cal in)
selected
Mode
Coupling
Source
Position
Display Mode
Magnifier
p-p auto
ac
internal
Set so trace starts at left
side of graticule,
main sweep
XI
Calibration Generator
4.
Connect the equipment under test and the test Amplitude 'I V
equipment to asuitable line voltage source. Turn all
equipment on and allow at least 20 minutes for the
equipment to stabilize.
Initial Control Settings
Set the following controls during warm-up time:
AM 502
STEP GAIN DC BAL
-1-100
DC OFFSET
FINE and COARSE
GAIN
CAL
HF -3dB
LF -3dB
AC
t- GNO
-AC
-GND
midrange
pushbutton out
midrange
100
fully clockwise (cal)
1MHz
DC OFFSET
pushbutton out
pushbutton out
pushbutton out
pushbutton in
PERFORMANCE CHECK PROCEDURE
NOTE
The oscilloscope vertical amplifier system gain,
the SChohm termination, and50-ohm attenuator
are required to be calibrated within 0.5% ac-
curacy prior to proceeding with Steps 1and 2.
The PG 506 calibration generator may be used
to set the system to 0.5% accuracy.
1. Check Amplifier Gain. Gain Accuracy is within
2%
a. Connect the calibration generator to the AM 502
input connector through a50-ohm cable, a50-ohm 10X
attenuator and 50-ohm terminator.
Oscilloscope
b. Connect a50-ohm cable from the AM 502 OUTPUT
connector to the vertical amplifier input connector
Intensity. Focus Set for well-defined trace
and normal brightness. c. Adjust the AM 502 DC OFFSET controls (FINE and
COARSE) until the OVERRANGE indicator light goes out.
Position the crt display to the center of the graticule with
the vertical amplifier position control.
Vertical Amplifier
Volts/Div 1Vd. Check—using the AM 502 GAIN and calibration
~Input dc generator amplitude settingsgivenin Table2-5. check the
Variable fully clockwise (cat) vertical deflection within the given limits.
REV AAUG 1979 2-5

Sptcillcatlon and Perlormance Check—AM 502
NOTE
The OVER RANGE indicator light must remain
otf during all switch settings. Adiust the DC
OFFSET controls as required during the check
procedure.
NOTE
Install both plug-in side covers and insert plug-
in into power module tor checking gain below
5K setting to minimize noise on the display.
Table 2-5
AMPLIFIER GAIN ACCURACY
AM 502
GAIN
Setting
IAM 502 I
IHF -3 dB ,
Switch Setting |
'- - --—
^
Calibration
Generator
Amplitude
Setting
Vertical
Deflection
in Divisiorts
100 1MHz 1V14.9 -5.1
200 1MHz 1.5 V!'4,9 -5.1
500 'Tmhz '.2V 4.9 -5.1
1K 1MHz .1 V4.9 -5.1
2K 1MHz 50 mV 4.9 -5.1
SK 1MHz 20 mV 4.9 -5.1
10K 10 kHz 10 mV 4.9 -5.1
20K 10 kHz 5mV 4.9 -5.1
50K 10 kHz 2mV !4.9 -5.1
100K 10 kHz 1mV !4.9 •5.1
2.
Check -i-100 Amplifier Gain Accuracy. Gain
Accuracy is within 2%
a. Disconnect all cables and repeat Step lparts a. b. c.
and d.
b. Set the AM 502 GAIN switch to 10K and the HF -3
dB switch to tMHz; push in the -rl00 pushbutton.
c. Set the calibration generator amplitude control to
1V. Adjust the AM 502 DC OFFSET control (FINE and
COARSE) until the OVERRANGE indicator light goes out.
d. Position the crt display to the center of the graticule
with the vertical amplifier position control.
eCheck—the crt display arnpiitude for 4 9to S1
divisions.
1. Disconnect the 50-ohm terminator from the AM 502
input connector and connect it tothe- input connector.
Push in the +input GND pushbutton and push and release
the -input GND pushbutton.
g. Check—repeat parts d. e, and fof this step.
h. Disconnect the 50-ohm termination, 10X attenuator,
and cable.
3.
Check Common Mode Rejection. Rejection Ratio
Is 100 dB. dc to 50 kHz
a. Connect adual-input connector cable between the
AM 502 *input and -input connector.
b. Set the AM 502 -MOO pushbutton out; the input
and -input AC and GND pushbuttons out. and the GAIN
switch to 100.
c. Set the AM 502 HF -3dB switch to .3 MHz and the LF
—3 dB switch to DC.
d. Set the vertical amplifier deflection factor for
lOmV/div.
e. Connect a50-ohm cable from the function
generator to the center connector of the dual-input
connector. Set the function generator for a 10 V. 50 kHz
sine-wave output signal, with DC offset set to 0at <1 V.
f. Adjust vertical amplifier positionto center display on
screen.
g.
Check—the crt display for one division of vertical
deflection or less.
4.
Check -fioO Common Mode Rejection. Rejection
Ratio is 50 dB. dc to 50 kHz
a. Disconnect the 50-ohm cable from the function
generator and connect it to the calibration generator
output. Press in the -rlOO pushbutton.
b. Set the vertical amplifier deflection factor for
100 mV/div.
c. Set the calibration generator for a100 volt, square-
wave output signal.
d. Check—crt display for 3.1 divisions or less of
verttcal deflection.
eDisconnect the dual-input connector and 50-ohm
cable from the AM 502 input connectors.
2-6 REV BSEP 1980

specification and Performance Check—AM 502
5. Check HF -3 dB Bandwidth. Accuracy la +1 dB.
-2 dB
a. Set the AM 502 HF -3 dB switch to 1MHz. the -
input pushbutton to <3NO. and 't-ioo pushbutton out.
b. Set the vertical amplifier deflection factor to 1V/div,
and the time-base sweep rate to 1ms/div.
c. Set the function generator controls for aSO mV. 1
kHz sine-wave output signal. (Use appropriate attenuation
to eliminate Input overdrive condition.)
d. Connect a50-ohm cable from the function
generator to the AM 502 +input connector. Adjust the
vertical deflection amplitude for afive-division display.
e. Set the function generator output frequency to 1
MHz.
f. Check—the amplitude of the crt display for 3.15 to
3.85 divisions.
NOTE
The specification in part fof this step must be
met before proceeding with part gof this step.
g. Check—the remaining settings of the HF —3 dB
switch, using Table 2-6 as reference. (Change time-base
sweep rate as needed for lower frequencies.)
Table 2-6
HF -3 dB BANDWIDTH ACCURACY
AM 502 Function Vertical
HF -3 dB Generator Deflection
Switch Setting Output Frequency In Divisions
.3 MHz 300 kHz 1315-3.85
.1 MHz 100 kHz 13.15-3.85
30 kHz
130 kHz 3.15-3.85
10 kHz '10 kHz 13.15-3.85
3kHz 3kHz 1315-3.85
1kHz 1kHz 3.15-3.85
3kHz 300 Hz 3.15-3.85
.1 kHz 1100 Hz 3.15-3.85
i. Set the HF -3 dB switch to 1MHz.
6. Check LF —3 dB Bandwidth. Accuracy is +1 dB,
-2 dB
a. Check—the settings of the LF -3 dB switch, using
Table 2-7 as reference. Adjust the time-base sweep rate to
obtain an appropriate display.
Table 2-7
LF -3 dB BANDWIDTH ACCURACY
AM 502 Function 1
Vertical
LF-3dB Generator IDeflection
Switch Setting Ou^ut Frequency 1In Divisions
10 kHz 10 kHz ii 3.15-3.85
1kHz 1kHz !! 3.15 -3.85
.1 kHz .1 kHz ;3.15-3.85
10 Hz 10 Hz 3.15-3.85
1Hz 1Hz !! 3.15 -3.85
NOTE
The components used in the .1 Hz position are
also used in the other po$/'fion$ of the switch:
therefore, the tolerance of the.1 Hz position is
checked.
b. PressintheAM 502 +input AC pushbutton. Set the
function generator controls for a 2 Hz output signal.
c. Check—the amplitude of the crt display for 3.15 to
3.85 divisions.
d. Disconnect the 50-ohm cable from the AM 502 -
input connector and connect it to the -Input connector.
e. Press in the AM 502 -*• input QND pushbutton and -
input AC pushbutton. Press to release the -input GND
pushbutton.
f. Check—the amplitude of the crt display for 3.15 to
3.85 divisions.
g. Set the LF —3 dB switch to the DC OFFSET position.
Press in the AM 502 -input GND pushbutton.
h. Disconnect the 50-ohm cable from the AM 502 -
input connector.
REV BSEP 1980 2-7

Sptcifkation and Performance Check—AM 502
7. Check Overtll Nolae (Tangentially Measured)
a. Set the AM 502 GAIN control to 100K; press in to
release the +input AC and GND pushbutton, and the -
input AC pushbutton.
b. Set the vertical amplifier deflection factor toS V/div.
Set the time-base sweep rate to tO^div. and the trigger
source switch to external.
c. Connect aSO-ohm termination to the AM 502 +
Input connector; conrwet four series-connected 10X
attenuators to the SO-ohm termination.
d. Connect a50<ohm cable from the calibration
generator fast-rise output connector to the end of d>e
attenuator string. Set the pulse duration control for 1ms.
e. Adjust the AM 502 DC OFFSET controls (FINE and
COARSE) until the OVER RANGE indicator light goesout.
f. Adjust the calibration generator pulse amplitude
control and observe two noise bands as shown in Fig. 2-1
A
(remove one attenuator if necessary, to produce the
desired display).
g. Decrease the calibration generator pulse amplitude
until the noise bands just merge. See Fig. 2-18.
h. Remove three of the attenuators and connect the
signal through the 50-ohm attenuator (including the 50-
ohm termination), to the vertical amplifier input and
measure the pulse amplitude. Calculate the tangentially
measured display noise as follows:
Noise (in pV) =Signal level (measured in part h)
Attenuation Removed
Typical figures are;
mm
mi1
1
1r'
MfMUaalMillli
m M 1N
tr
mmmpim
mmH
(A)
Fig. 2-1. Typical display of (A) two noisa bands and (B) nolsa
bands marpMl.
I. Disconnect all cables and equipment.
12 mV
10"’ =12 XlO"* =l2(iV of noise This completes the Performance Check of the AM 502
Differential Amplifier.
2-8 REV AAUG 1979

Section 3—AM S02
ADJUSTMENT
Introduction
This adjustment procedure is to be used to restore the
AM 502 to the original performance specification. Adjust-
ment need not be performed unless the instrument fails to
meet the Performance Requirements of the Electrical
Characteristics listed in the Specification section, or the
Performance Check cannot be completed satisfactorily.
Completion of all adjustment steps in this procedure
ensures that the instrument will meet the performance
requirements listed in the Specification section. However,
to fully ensure satisfactory performance, it is recommend-
ed that the Performance Check be performed after any
adjustment is made.
Services Available
Tektronix. Inc. provides complete instrument repair
and adjustment at local Field Service Centers and at the
Factory Service Center. Contact your local Tektronix
Field Office or representative for further information.
Test Equipment Required
The test equipment listed In Table 3-1, or equivalent, is
required for adjustment of the AM 502. Specifications
given for the test equipment are the minimum necessary
for accurate adjustment and measurement. All test equip-
ment is assumed to be correctly calibrated and operating
within specification.
If other test equipment is substituted, control settings
or calibration setup may need to be altered to meet the
requirements of the equipment used.
Aflexible plug-in extender. Tektronix Part No. 067-
0645-03. is useful fortroubleshooting or adjusting the AM
502; however, the complete Adjustment Procedure can be
performed without use of the extender. Remove the power
module cabinet to make adjustments to the AM 502 inside
the power module.
REV. BMAR 197S 3-1