Tektronix PS 503A User manual

Tektronix
COMMITTED TO EXCELLENCE
PS 503A
DUAL
POWER SUPPLY
INSTRUCTION MANUAL

TEKTRO NIX ®
■
PS 503A
DUAL
PO WER SUPPLY
INSTRUCTION MANUAL
Tektronix, Inc.
P.O. Box 500
Beaverton, Oregon 9 0
Serial Number _______________________
0 0-1834-01
First Printing SEPT 19 4

PS 503A
TABLE
O CONTENTS
SECTION 1
SECTION 2
OPERATING INSTRUCTIONS
SPECIFICATION AND PERFORMANCE CHECK
Page
1-1
2-1
WARNING |
The remaining portion of this Table of Contents lists servicing instructions that
expose personnel to hazardous voltages.- These instructions are for qualified
service personnel only.
SECTION 3 ADJUSTMENT
3-1
SECTION 4
MAINTENANCE AND INTERFACING INFORMATION
4-1
SECTION 5
CIRCUIT DESCRIPTION '
5-1
SECTION 6
REPLACEABLE
ELECTRICAL PARTS LIST
6-1
OPTIONS
SECTION
DIAGRAM AND CIRCUIT BOARD ILLUSTRATION
-1
SECTION 8
REPLACEABLE MECHANICAL PARTS LIST AND
EXPLODED VIEW
8-1
CHANGE INFORMATION
i

Fig. 1-1. PS 503A Dual Power Supply plug-in module.
PS 503A

Section 1 — PS 503A
OPERATING
INSTRUCTIONS
INTRODUCTION
Description
The PS 503A is a dual 0 to 20 V d c constant-voltage,
current-limited, floating power supply. It is designed to
operate in the high-power compartment of the TM 504 or
TM 506 Power Module. In the high-power compartment, it
provides a floating dual 0 to 20 Vdc at 1.0 A. Operating in a
standard compartment of a TM 500 Series Power Module,
the PS 503A supplies a floating dual 0 to 20 V d c at
400 mA.
The supply is designed for conveniently powering
complementary and linear integrated circuits such as
operational and differential amplifiers as well as differen 
tial comparators. A ground referenced +5 V auxiliary
supply (suitable for bipolar logic, light-emitting diodes,
incandescent displays and similar applications) is also
included. With the floating supply available for powering
discrete interface circuits and level shifting, the PS 503A
can be used for many digital/analog applications.
The plus and minus outputs from the dual floating
power supplies are independently variable or^both
variable at a constant ratio by a common contro l. Each
supply provides either a plus or minus 0 to 20 V d c with
respect to the common terminal, By connecting across the
plus and minus terminals, the PS 503A can provide 0 to
40 V d c . Either terminal may be grounded or floated to
350 V (de + peak ac). Each supply also features con 
tinuously variable current limiting from less than 50 mA to
400 mA (standard compartment) or 1 A (high power
compartment) at both 20 V and 40 V output.
diode as well as a dimming of the VOLTS indicator light if
the supply output voltage is above approximately 10 V.
These functions are easily verified by momentarily shor 
ting the output of the supply.
Installation and Removal
CAUTION (
Turn the power module off before inserting the plug 
in; otherwise, damage may occur to the plug-in
circuitry. Because of the high current drawn by the
PS 50 A, it Is also recommended that the power
module be turned off before removing the PS 50 A.
Refer to Fig. 1-2. Check to see that the plastic
barriers on the interconnecting jack of the selected
power module compartment match the cut-outs in
the PS 50 A circuit board edge connector.
A li gn the PS 503A 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 PS 503A, pull on the release latch
located in the lower left corner, until the interconnecting
jack disengages and the PS 503A will slide out.
The presence and variability of the output voltage is
verified by the VOLTS indicator light on the front panel.
The brightness of this light varies with output voltage. A
panel-mounted light-emitting diode (LED) indicates when
the PS 503A is operating in a standard compartment of a
TM 500 Series Power Module and the output current is
limited to a maximum of 400 mA. Other panel-mounted,
light-emitting diodes indicate when either the + or —
supply goes into current-limiting. Hard limiting is in 
dicated by maximum brightness of the light-emitting
Controls and Connectors
Refer to Fig. 1-3. Even though the PS 503A is fully
calibrated and ready to use, the functions and actions of
the controls and connectors should be reviewed before
attempting to use it. Press the OUTPUT button to apply
power to the PS 503A.
REV. C MAR 1977
1-1

Operating Instructions — PS 503A
ig. 1-2. Plug-in module installatlon/removal.
/
OPERATING CONSIDERATIONS
Overheating
The PS 503A is designed to operate at an ambient
temperature from 0°C to +50" C. However, when
operating several power supplies in a multi- plug-in power
module, especially at low output voltages, or when
operating close to other heat-producing equipment, inter 
nal temperature may exceed safe limits and actuate a
thermal cutout in the power module. Refer to the power
module instruction manual for more complete informa 
tion.
Grounded and loating Operation
The PS 503A is a + and — 20 V "floating" supply since
no internal connections are made to either the chassis or
ground. The supply can thus be used as a positive or
negative supply by simply connecting between the com 
mon and the negative o r positive output terminal.
However, there may be undesirable effects caused by
grounding the supply to the chassis while the load is
grounded at some point removed from the supply chassis.
For example, if a remote load is connected as shown in Fig.
1-5, ground currents containing the power-line frequency
could result and create excessive noise and ripple in series
with the load. Thus, floating operation is recommended to
ensure against problems caused by undersirable ground
currents.
Load and Monitor Connections
Improper connections between the power-supply out 
put and the load (s) or monitoring device(s) are a common
cause of errors. Multiple loads or monitoring devices must
be connected directly to the output terminals with
separate pairs of leads as shown in Fig. 1-4. Avoid using
clip leads, since their contact resistance can exceed the
output impedance of the PS 503A and cause significant
measurement error.
Reverse Current Loading
In some bias supply and digital circuitry applications
the load might behave as a current source for part of its
operating cycle. Since the output circuit of a series-
regulated supply is unidirectional, current will not pass in
the opposite direction except through undesirable paths.
The internal reverse-current diodes conduct only when
the PS 503A terminal voltage reverses and therefore will
not work when the voltage is correctly polarized. Connec-
1-2
REV. A MAR 19

Operating Instructions — PS 503A
VOLTS DUAL
TRACKING Control
VOLT:
CURRENT LIMIT
VOLTS Controls
and Indicators
Variable coarse and fine
controls provide con 
tinuously variable + or —
voltage selection from the
respective 0-20 volt
supply. The presence and
variability of output
voltage is verified by
voltage indicator lights
(OUTPUT button
pressed). Brightness of
lights varies with output
voltage.
400 mA LIMIT Indicator
Light emitting diode in 
dicates when PS 503A Is
installed in a standard
compartment of a power
module, limiting the
current output.
Floating Output
Terminals
5-way binding post ter 
minals that provide either
a positive 0-20 volts
between the binding post
on the right (red) and
COMMON, or a negative
0-20 volts between the
binding post on the left
(green) and COMMON.
When the PS 503A is in 
stalled in the high power
compartment of a TM 504
or TM 506 power module
that has a high power
compartment, the current
available at either the +or
— outputs is from less
than 100 mA to at least
1 A. When the PS 503A Is
installed in a standard
compartment, the current
available is from less than
100 mA to at least
400 mA. 0 to 40 volt out 
put is obtained between
the + and — output ter 
minals.
+5 Ground-Referenced
Output Terminals
5-way binding-post termi 
nals that provide a
ground-referenced +5 V,
1 A, fixed output.
VOLTS
DUAL TRACKING
(PULL)
When pulled out, varies
both the + and — outputs
from 0 volts to the value
set on the + and — VOLTS
controls. The ratio be 
tween the + and - outputs
is maintained throughout
the range of the VOLTS
DUAL TRACKING con 
trol.
OUTPUT Pushbutton
When pressed, applies
power to both 0-20V
binding post terminals
and the +5V binding post
terminal.
CURRENT LIMIT
Controls and Indicators
Continuously variable
controls that select the +
and — output current limit.
Light-emitting diode in 
dicates when hard
limiting occurs.
1834 ’ 05
REV. B MAR 19
Fig. 1-3. PS 503A controls and connectors.

Operating Instructions — PS 503A
NOTE
Supply is connected for 20 to 40 V output.
ig. 1-4. Monitor and load connections.
NOTE
Supply is connected for 0 to 40 V output.
ig. 1-6. Reverse current shunt (Rs) with active load.
ting a shunt resistor (Rs) as shown in Fig.1-6 provides an
external, reverse-current path to the power supply
sources or delivers current only.
Over-voltage
The PS 503A is protected from over-voltage conditions
by an over-voltage protection circuit that shuts down the
power supply when the voltage rises to about 26 V d c .
NOTE
The point at which the overvoltage protection blows
the fuse may be changed for specific applications by
changing the Zener diode.
OPERATION
The following steps demonstrate the use of the
PS 503A controls and connectors.
1. Install the PS 503A into (preferably) the high-power
compartment of the power module.
2. Press the OUT button to apply power to the
PS 503A. Observe that the + and - VOLTS indicator lights
come on (the lights will be very dim at low voltages).
Single Supply Operation (±20 V Maximum)
1. Set the + and — VOLTS controls for approximately
2 V.
NOTE
Supply is connected for 0 to 40 V output.
2. Turn the CURRENT LIMIT controls fully ccw (to
protect the ammeter). Connect an ammeter between the
common terminal and the + or — terminal and adjust the
appropriate CURRENT LIMIT control for the maximum
desired current output.
ig. 1-5. Ground loop created by grounded remote lead.
1-4
REV. A MAR 1977

Operating Instructions — PS 503A
3. Remove the ammeter. Connect the load between the
common terminal and the + or — terminal. Adjust the + or
— VOLTS control for the desired output.
Combined Supply Operation (40 V Maximum)
1. Set the + and — VOLTS control for approximately
2 V and turn the CURRENT LIMIT controls fully ccw (to
protect the ammeter).
2. Connect an ammeter between the + and — ter 
minals. First adjust one CURRENT LIMIT control for the
maximum desired current output; then adjust the other
CURRENT LIMIT control until the CURRENT LIMIT
indicator just reaches maximum brightness, i.e., both
supplies at the same CURRENT LIMIT setting.
3. Remove the ammeter. Connect the load between the
+ and - terminals and set the + and — VOLTS controls so
that both settings added together equal the desired output
voltage. (See Dual-Tracking Operation for varying the
output with the VOLTS DUAL TRACKING control.)
Stair-Step Operation
The PS 503A can be operated to provide a "stair-step"
output characteristic by choosing certain load limits and
control settings. For example, Fig. 1- shows the stair-step
output from the PS 503A when a variable load (R l ) is
connected between the + and — output terminals. With
each supply set for maximum voltage and current (40 V,
1 A) the output voltage remains constant from open circuit
until the load reaches approximately 40 Ω as illustrated by
the solid line in Fig. 1- . At this crossover point, the output
voltage decreases with the load and the output current is
limited at 1 A. Therefore, below approximately 40 Ω , both
supplies act as current sources with output voltage
variable with the load. Since both supplies are set for the
same output voltage, each supply shares equally in the
power output PR. If one supply is set for a lower output
voltage than the other, output power is shared at the same
ratio as the output voltage.
Now, by setting supply E 2 for a current limit of 0.5 A and
varying the load over the same range, the supplies act as
constant-voltage sources until the load reaches ap 
proximately 80 Ω . At that crossover point, the supply set
for 0.5 A (E 2 ) becomes a current source and its output
Dual-Tracking Operation
When pulled out, the VOLTS DUAL TRACKING control
varies the output of both supplies at a constant ratio from
zero to the value set on the + and — VOLTS controls. For
example, if the + and — VOLTS controls are set for
maximum output (approximately 20 V), both outputs can
be varied from zero to 20 V with the VOLTS DUAL
TRACKING control (1:1 ratio). Likewise, if one supply is
set for 10 V and the other for 20 V, each 1 V change in the
10 V output will be matched by a 2 V change in the 20 V
output (2:1 ratio).
Note also that no matter where the VOLTS DUAL
TRACKING control is set, the outputs will return to the
voltage selected by the + and — VOLTS control when the
VOLTS DUAL TRACKING control is pushed in. Therefore,
rapid selection of two preset outputs from each supply is
achieved by merely switching the VOLTS DUAL
TRACKING control in or out.
When the + and — supplies are connected as described
under Combined Supply Operation, the VOLTS DUAL
TRACKING control will vary the output from zero to the
value selected by the + and - VOLTS controls added
together.
CURRENT IN AMPERES
ig. 1-7. Output characteristics with various currents, voltages,
and loads.
REV. B MAR 19
1-5

Operating Instructions — PS 503A
voltage decreases with the load. At approximately 40 Ω
and 20 V, supply E 2 no longer contributes to the power
output. Subsequently, supply Ei supplies all the output
power and operates as a constant-voltage source with
output current variable with the load. Then, at ap 
proximately 20 Ω , supply Ei crosses over and becomes a
current source at its maximum output of 1 A. Thus, by
choosing the appropriate load limits and control settings,
any of the four operating characteristics is possible.
A second stair-step output can be preselected and
switched in or out with the VOLTS DUAL TRACKING
control (see Dual-Tracking Operation for details on the
function of the VOLTS DUAL TRACKING control).
Parallel-Connected Supplies
CAUTION
Parallel operation is not recommended unless a
forward biased diode capable of handling the re 
quired current and voltage is inserted between each
power supply and the load. Failure to do this may
cause power supply damage.
The outputs of two or more PS 503's can be connected
in parallel as shown in Fig. 1-9 to obtain an output current
equal to the sum of the output currents from each supply.
Each supply must be adjusted individually to obtain the
desired output current.
Series-Connected Supplies
The outputs of two or more PS 503A ’ s can be con 
nected in series as shown in Fig. 1-8 to obtain an output
voltage equal to the sum of the output voltages from each
supply. Each supply must be adjusted individually to
obtain the desired output voltage (see Dual-Tracking
Operation for varying the output of both supplies with the
VOLTS DUAL TRACKING control).
NOTE
The PS 50 A has internal diodes connected across
the output to protect the series-connected supplies
against reverse polarity if the load is shorted, or one
of the supplies is not on.
NOTE
The + and — supplies are internally connected in
series. Therefore, the + and — supplies cannot be
externally connected in parallel to obtain an output
current equal to the sum of the currents from each
supply.
One supply should be set for the desired output voltage
and the other for a slightly higher voltage. The supply set
for the desired voltage will then become a constant voltage
source, while the supply with the higher voltage output
becomes a current source (due to automatic crossover),
which results in their output voltage decreasing to that of
the supply with the lowest output voltage.
ig. 1-8. Supplies series-connected.
ig. 1-9. Supplies parallel-connected.
1-6
REV. B MAR 19

Section 2 — PS 503A
SPECI ICATION AND
PER ORMANCE CHECK
SPECI ICATION
Performance Conditions
The electrical characteristics are valid only if the
PS 503A has been calibrated at an ambient temperature
between +20° C and +30° C and is operating at an ambient
temperature between 0°C and +50° C unless otherwise
noted.
Items listed in the Performance Requirements column
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
Performance Requirements
Supplemental Information
Plus and Minus 20 V loating Supplies
Voltage Outputs
0 V (±100 mV) to at least 20 V d c
(20.1, — .1, +.4 V de) with re 
spect to common terminal, or 0 V
to at least 40 V d c across the
plus and minus terminals.
Outputs either independently
variable or both variable at
a constant ratio of a common
control (Dual Tracking).
Variable Current
Limiting
Less than 100 mA to at least 1 A
when installed in a high-power
compartment.
Maximum limit; 1.5 A
Less than 100 mA to at least 400 mA
when installed in a low power
compartment.
Maximum limit; 600 mA
Minimum Resolution
50 mV
)
2-1

Specification and Performance Check — PS 503A
+5 V Ground Reference Supply
Table 2-1 (cont)
Characteristics
Performance Requirements
Supplemental Information
Load Regulation
Within 3 mV with a 1 A load change. Within 1 mV with a 400 mA load
change.
Transient Recover
≤20 µs for a constant voltage to
recover within 20 mV for a
nominal output voltage after a
400 mA change in output current.
Line Regulation
Within 5 mV for a ±10% line
voltage change.
Ripple and Noise
(2 Hz to 2 MHz instrument
not in current limiting.)
3 mV peak-to-peak or less with a
1 A load.
1 mV peak-to-peak or less with
a 400 mA load (noise and
ripple increase unpredictably
when current is being limited).
Temperature Coefficent 0.025%/° C or less.
Stability 0.1% +5 mV (or less) of drift in 8
hours. Line voltage, load and tem 
perature held constant.
Supply Isolation from
Ground
350 V (d c + peak ac).
Dual Tracking Mode
Offset Error
If the two supplies are set indepen 
dently to any given voltage ratio, and
if both supplies are then monitored
and varied a given amount (by using
the VOLTS DUAL TRACKING control),
the two supplies will maintain the
same voltage ratio as initially set
within 50 mV; until one supply reaches
either 0 v' or 20 V.
Output
4. 5 V d c to 5.25 V d c with a 5 ohm
load.
Measured at a temperature be 
tween +20° C and +30° C.
Load Regulation
Within 100 mV with a 1 A load change.
Line Regulation
Within 50 mV for a ±10% line volt 
age change.
Measured at a temperature be 
tween +20° C and +30° C.
Ripple and Noise
(2 Hz to 2 MHz)
5 mV peak-to-peak or less with a 1 A
load.
Long Term Stability
0.5% or less of drift.
Overload Protection Fixed (automatic) current limiting
and over-temperature shutdown.
2-2
REV. A, AUG. 1977
i

Specification and Performance Check — PS 503A
Table 2-2
ENVIRONMENTAL
Characteristics
Performance Requirements
Supplemental Information
Temperature
Operating
Storage
0°C to +50° C.
-40° C to + 5° C.
Altitude
Operating
Storage
To 15,000 feet.
To 50,000 feet.
Vibration
Operating and
Non-Operating
With the instruments complete and oper 
ating, vibration frequency swept from
10 to 50 to 10 Hz at 1 minute per sweep.
Vibrate 15 minutes in each of the three
major axes at 0.015" total displace 
ment. Hold 3 minutes at any major re
sonance, or if none, at 50 Hz. Total
time, 54 minutes.
Shock
Operating and
Non-Operating
30 g ’ s, 1/2 sine, 11 ms duration, 2
shocks in each direction along 3 major
axes, for a total of 12 shocks.
Table 2-3
PHYSICAL
Characteristic
Information
Overall Dimensions (measured at maximum points)
Height 5.0 inches
12. cm
Width
2.6 inches
6.6 cm
Length
11. 5 inches
29. cm
Net Weight (Instrument only)
1 lb 13 oz
821 grams
2-3

Specification and Performance Check — PS 503A
PER ORMANCE CHECK
Introduction
This procedure checks the electrical characteristics of
the PS 503A that appear in the Specification portion of this
section. Limits and tolerances given in the Supplemental
Information column are provided for user and service
information only, and should not be interpreted as re 
quirements for this Performance Check.
The electrical characteristics are valid only if the
instrument has been calibrated at an ambient temperature
between +20° C and +30° C, and is operated at an ambient
temperature between 0°C and +50° C unless otherwise
noted.
Limits and tolerances given in this Performance Check
are for the instrument under test and do not include test
equipment error. Limits and tolerances in this procedure
are instrument performance requirements only if stated as
such in the Specification portion of this section.
Test Equipment Required
The following test equipment, or equivalent, is required
to perform the performance check and adjustment
procedure. 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. All test equipment is
assumed to be operating within tolerance.
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.
Table 2-4
LIST O TEST EQUIPMENT REQUIREMENTS
Description
Performance
Requirements Application
Example
Oscilloscope
Bandwidth, d c to 2 MHz;
minimum deflection factor,
1 mV/div; sweep rate,
10 ms/div to 1 µ s/div.
Used throughout pro 
cedure to provide
display.
Tektronix 5110,
5B10N
Oscilloscope
System.
Digital voltmeter
Range, zero to 1000 volts;
accuracy, within 0.1%.
Voltage measurements.
Tektronix DM 501
Digital Multimeter.*
Power Module
Four compartments or more,
with one high-power
compartment.
All tests.
Tektronix TM 504
or TM 506.
Autotransformer
with ac volt 
meter
Capable of supplying an
output voltage from 90
to 132 volts, ac; 120 W
of power at the upper
limits.
Regulation and
ripple checks.
General Radio
W10MTR3W Variac
Autotransformer.
Coaxial cable
Impedance, 50 Ω ; length,
42 inches; connectors, bnc.
Provides signal inter 
connection.
Tektronix Part No.
012-005 -01.
Patch cord
(2 required)
Banana-plug-jack to banana 
plug-jack; length, 18 inches.
Provides signal inter 
connection.
Tektronix Part No.
012-0031-00 (black),
012-0039-00 (red).

Specification and Performance Check — PS 503A
Table 2-4 (cont)
Description
Performance
Requirements
Application
Example
Adapter
Bnc female to dual-banana
plugs.
Provides signal inter 
connection.
Tektronix Part No.
103-0090-00.
Load resistor
20 Ω , 20 W, 5%,
(two 10 Ω , 10 W in series).
Load tests.
Tektronix Part No.
308-0246-00.
Load resistor
5 Ω , 5 W, 5%. Load tests.
Tektronix Part No.
308-01 9-00.
Resistor
(2 required)
4.99 k Ω , 1/2 W, 1%
or better.
Dual tracking detector
test.
Tektronix Part No.
323-0260-00.
1X passive probe
Compatible with 5A-series
amplifiers used in
oscilloscope.
Provides signal inter 
connection.
Tektronix P6028
Probe.
'Requires TM 500-Series Power Module.
Preliminary Procedure
1. Ensure that all test equipment and the PS 503A
under test are suitably adapted to the line voltage to be
applied. Refer to the installation section of the power
module manual.
2. Be certain that the POWER switch on the power
module is off and that the OUTPUT pushbutton on the
PS 503A is in the out position.
3. Install the PS 503A in the far right (high power)
compartment of the power module.
4. Connect the power module to the autotransformer
and connect the autotransformer to the line voltage
source. Set the autotransformer voltage output control for
zero volt output.
5. Set all front-panel controls on the PS 503A fully
counterclockwise (ccw). Apply power to the power
module and press in the OUTPUT pushbutton on the
PS 503A. Push the PS 503A VOLTS DUAL TRACKING
control in.
6. Adjust the autotransformer to the nominal line
voltage and check that the two VOLTS indicator lights on
the PS 503A are on.
. Set the vertical deflection factor for 1 mV/div and
sweep rate for 5 ms/div on the test oscilloscope. Use ac
coupling for the vertical amplifier unit during this
procedure.
8. Connect all test equipment to a suitable line voltage
source.
9. Turn on all test equipment and allow at least twenty
minutes for the equipment to warm-up and stabilize.
NOTE
During warm-up time, attach banana pins to the
leads of the 20 Ω and 5 Ω load resistors so that they
can be inserted in the holes of the dual-banana
adapter. This allows the load resistors to be con 
nected as close as possible to the output terminals
on the PS 50 A so contact resistance is kept to a
minimum.
2-5

Specification and Performance Check — PS 503A
Performance Check Procedure
1. Check 0-20 Volt Output Voltage
a. Check that all controls on the PS 503A front panel
are fully ccw and that the 400 mA MAX indicator light is off
(this light should remain off as long as the PS 503A is
installed in the high-power compartment of the power
module). Also check that both CURRENT LIMIT indicator
lights are off. (For instruments SN B022064-below, these
lights may be on; if so, adjust the appropriate CURRENT
LIMIT control cw just enough to turn them off).
b. Set the digital voltmeter to the 2 volts d c range. Use
patch cords to connect the +20 V floating output ter 
minals of the PS 503A to the digital voltmeter input
terminals; connect the red patch cord from the 0 — 20V red
binding post to the digital voltmeter high input terminal,
and the black patch cord from the COMMON (black)
binding post to the digital voltmeter low input terminal.
c. Check that the PS 503A + VOLTS controls are fully
ccw and check for a meter reading of .0000, within
±100 mV.
d. Set the digital voltmeter to the 200 volts d c range
and set the PS 503A + VOLTS controls fully cw.
e. Check — for a meter reading of at least +20.1 volts,
but less than +20.4, volts.
f. Adjust the PS 503A + VOLTS controls fully ccw and
move the red patch cord from the 0 — 20V red binding post
to the 0 — 20V green binding post on the PS 503A.
g. Repeat parts 1c through 1e, using the PS 503A
— VOLTS controls to check the — 20 V supply.
b. Disconnect the red patch cord from the digital
voltmeter high input terminal and set the digital voltmeter
to the 2000 mA de range. Reconnect the red patch cord to
the digital voltmeter high input terminal.
c. Check — for a current reading of less than 100 mA
for the +20 V supply. The PS 503A + CURRENT LIMIT
light should be on.
d. Move the red patch cord from the PS 503A 0 — 20V
red binding post to the PS 503A 0 — 20V green binding
post.
e. Check — for a current reading of less than 100 mA
for the -20 V supply. The PS 503A - CURRENT LIMIT
light should be on.
f. Rotate the PS 503A - CURRENT LIMITcontrol fully
cw.
g. Check — for a current reading of more than
1000 mA, but less than 1500 mA for the — 20 V supply.
h. Reconnect the red patch cord to the PS 503A 0 — 20V
red binding post and rotate the PS 503A + CURRENT
LIMIT control fully cw.
i. Check — for a current reading of more than 1000 mA,
but less than 1500 mA for the +20 V supply.
j. Set all controls on the PS 503A front panel fully ccw
and retain the digital voltmeter connections to the
PS 503A.
h. Set the PS 503A — VOLTS controls fully ccw and
move the red patch cord back to the 0-20V red binding
post on the PS 503A. Check to be certain that all PS 503A
front-panel controls are fully ccw.
2. Check Variable Current Limiting
a. Adjust the PS 503A + VOLTS controls for +5.0 V
output. Move the red patch cord to the PS 503A 0 — 20V
green binding post and adjust the PS 503A — VOLTS
controls for — 5.0 V output. Move the red patch cord back
to the PS 503A 0 — 20V red binding post.
3. Check Load Regulation
a. Disconnect the red patch cord from the digital
voltmeter input terminal and set the digital voltmeter to the
20 volts d c range. Reconnect the red patch cord to the
digital voltmeter high input terminal; the meter reading
should indicate approximately zero volts. Both CURRENT
LIMIT lights on the PS 503A front panel should be off and
remain off during the load regulation check.
b. Rotate the CURRENT LIMIT control on the PS 503A
fully cw.
2-6

Specification and Performance Check — PS 503A
c. Adjust the PS 503A + VOLTS fine and coarse
controls for a meter reading between +19.900 and +19.980
volts. Note and record the exact open-circuit voltage
' reading before applying the adapter (with load resistor
attached) in part d of this step.
d. Insert the leads of the 20 Ω , 5% resistor into the
holes of a dual-banana plug adapter and connect the
adapter to the patch cord jacks, which remain connected
to the PS 503A 0 — 20V red and the COMMON binding post
terminals. Observe correct polarity for the adapter (GND
to COMMON).
e. CHECK — that the meter reading does not change
more than 3 mV (three counts of the most right-hand
digit).
NOTE
If the reading on the digital voltmeter changes by
more than mV, another 20 Ω , load resistor having a
resistance value closer to 20 Ω should be used, or
the voltage output from the PS 50 A can be reduced
to +19.000 (step c).
f. Remove the adapter (with load resistor) from the
PS 503A patch cord jacks. Move the red patch cord to the
0 — 20V green binding post terminal.
b. Adjust the autotransformer 10% below and 10%
above the nominal line voltage setting.
c. Check — that the voltage reading displayed on the
digital voltmeter does not change more than ±5 mV (5
counts) for each 10% line voltage change. Readjust the
autotransformer to the nominal line voltage.
d. Remove the adapter (with load resistor) from the
patch cord jacks. Move the red patch cord to the 0-20V
red binding post terminal. Reconnect the adapter (with
load resistor) to the patch cord jacks. Observe correct
polarity for the adapter (GND to COMMON).
e. Note the exact voltage reading displayed on the
digital voltmeter with the adapter and load resistor still
attached to the 0 — 20V red and COMMON binding post
terminals (+19.900 to +19.980 volts).
f. Adjust the autotransformer 10% below and 10%
above the nominal line voltage setting.
g. Check — that the voltage reading displayed on the
digital voltmeter does not change more than ±5 mV (5
counts) for each 10% line voltage change. Readjust the
autotransformer to the nominal line voltage.
g. Adjust the PS 503A — VOLTS fine and coarse
controls for a meter reading between — 19.900 and -19.980
volts. Note and record the exact open-circuit voltage
reading before applying the adapter (with load resistor
attached) in part h of this step.
h. Insert the leads of the 20 Ω , 5% resistor into the
holes of a dual-banana adapter and connect the adapter to
the patch cord jacks, which remain connected to the
PS 503A 0 — 20V green and the COMMON binding post
terminals. Observe correct polarity for the adapter (GND
to COMMON).
5. Check Ripple and Noise
a. Disconnect the patch cords from the PS 503A
0 — 20V red and COMMON binding post terminals and
reconnect the dual-banana adapter (with load resistor)
directly to the 0 — 20V red and COMMON binding post
terminals; observe correct polarity of the adapter (GND to
COMMON).
b. Connect the output of the adapter to the vertical
input of the oscilloscope, using a 42-inch bnc cable. Set
the oscilloscope vertical deflection factor for 1 mV/div
(calibrated).
i. Check — that the meter reading does not change
more than 3 mV (three counts of the most right-hand
digit).
4. Check Line Regulation
a. Note the exact voltage reading displayed on the
digital voltmeter with the adapter and load resistor still
attached to the PS 503A 0-20V green and COMMON
binding post terminals ( — 19.900 to — 19.980 volts).
c. Slowly adjust the autotransformer output voltage
10% below and then 10% above the nominal line voltage.
d. Check — the signal display on the oscillosocpe for
less than 3 mV peak-to-peak (within three vertical
divisions) at all points of the specified voltage limits.
e. Readjust the autotransformer to the nominal line
voltage.
@
2-7

Specification and Performance Check — PS 503A
f. Connect the adapter (with load resistor attached) to
the PS 503A 0 — 20V green and COMMON binding post
terminals; observe correct polarity of the adapter (GND to
COMMON).
j. Set the PS 503A VOLTS DUAL TRACKING control
fully ccw and push the control knob in. Disconnect both
patch cords and the two resistors from the binding post
terminals.
g. Repeat steps 5c through 5e to check the ripple and
noise of the PS 503A — 20 V supply.
h. Readjust the autotransformer to the nominal line
voltage and disconnect all connections from the PS 503A.
6. Check Dual Tracking Mode Offset Error
a. Pull out the PS 503A VOLTS DUAL TRACKING
control and set it fully ccw to ensure minimum output
voltage while connecting the resistors.
b. Connect the two 4.99 k Ω , 1% resistors in series
between the PS 503A 0 — 20V green and 0 — 20V red binding
post terminals. Do not connect the junction of the two
resistors to the COMMON terminal or the chassis.
c. Connect the black patch cord from the digital
voltmeter low terminal to the PS 503A COMMON binding
post, and the red patch cord from the digital voltmeter high
terminal to the PS 503A 0 — 20V red binding post.
d. Set the PS 503A VOLTS DUAL TRACKING control
fully cw and adjust the PS 503A + VOLTS controls for a
meter reading of +18 V, ±0.1 volt.
e. Connect the red patch cord to the 0 — 20V green
binding post and adjust the PS 503A — VOLTS controls for
a meter reading of — 18 V, ±0.1 volt.
f. Disconnect the red patch cord from the 0 — 20V green
binding post and connect it to the junction of the two
4.99 kO, 1% resistors. Check that the digital voltmeter
indicates a d c voltage less than 1 V.
g. Set the digital voltmeter to the 2-volts de range and
adjust either the + VOLTS or — VOLTS controls on the
PS 503A to obtain a meter reading of 0 V d c (±100 mV).
h. Adjust the PS 503A VOLTS DUAL TRACKING
control slowly from cw to ccw.
7. Check +5 Volt Output Voltage
. f
a. Connect the digital voltmeter between the +5V@1A
ground referenced red binding post and the ground white
binding post.
b. Push in the OUTPUT button and check that the two
VOLTS indicator lights are on.
c. Check — for a meter reading of +4. 5 to +5.25 volts.
d. Connect a 50 Ω resistor between the +5V@1A
ground referenced red binding post and the ground
(white) binding post.
e. Check — that the meter reading does not change by
more than 100 mV.
8. Check +5 Volt Output Voltage Regulation
a. Adjust the autotransformer output voltage from the
low limit to the high limit as indicated in Table 2-5.
b. Check — that the digital voltmeter reading does not
change more than 50 mV for a plus 10% or minus 10% line
voltage change.
c. Disconnect the digital voltmeter.
d. Connect the probe of the test oscilloscope between
the +5V binding post and the ground (white) binding post.
e. Adjust the autotransformer output voltage from the
low limit to the high limit as indicated in Table 2-5.
f. Check — the test oscilloscope display for not more
than 5 mV peak-to-peak ripple and noise.
g. Return the autotransformer to the nominal line
voltage setting.
i. Check — that the meter reading remains within
±25 mV of zero volts.
h. Disconnect the test oscilloscope probe from the
binding posts.
2-8

Specification and Performance Check — PS 503A
i. Press and release the PS 503A OUTPUT button to
turn off the power to the PS 503A.
Table 2-5
POWER MODULE UNIVERSAL TRANS ORMER
Line
Selector
Block
Position
Regulating Ranges
110-Volts Nominal 220-Volts Nominal
L
90 VAC to 110 VAC 180 VAC to 220 VAC
M
99 VAC to 121 VAC
198 VAC to 242 VAC
H
108 VAC to 132 VAC 216 VAC to 264 VAC
Line Fuse
Data 1.6 A slow-blow
0.8 A slow-blow
9. Check Variable Current Limiting
a. Turn the power off to the TM 500 Series Power
Module and remove the PS 503A from the high-power
compartment and install the PS 503A in the low-power
compartment.
f. Set the PS 503A + and — CURRENT LIMIT controls
fully cw.
g. Check — that the digital voltmeter indicates a
current reading of more than 400 mA, but less than
600 mA. The + CURRENT LIMIT light should be on.
h. Move the red patch cord from the 0 — 20V red binding
post to the 0-20V green binding post.
i. Check — that the digital voltmeter display indicates a
current reading of more than 400 mA, but less than
600 mA. The - CURRENT LIMIT light should be on.
j. Set the PS 503A - CURRENT LIMIT control fully
ccw.
k. Check — that the digital voltmeter indicates a current
reading of less than 100 mA. The — CURRENT LIMIT light
should remain on.
b. Turn on the power to the power module and press
the PS 503A OUTPUT button in. Set all front panel
controls fully ccw and allow approximately three minutes
for the equipment to stabilize.
c. Check — that the 400 mA MAX indicator light is on.
d. Adjust the PS 503A + VOLTS and — VOLTS coarse
controls to the 4 V position (leave the fine controls fully
ccw).
e. Set the digital voltmeter to the 2000 mA position and
connect the black patch cord from the digital voltmeter
low terminal to the PS 503A COMMON binding post and
the red patch cord from the digital voltmeter high terminal
to the PS 503A 0 — 20V red binding post.
I. Move the red patch cord from the 0 — 20V green
binding post to the 0 — 20V red binding post and set the
PS 503A + CURRENT LIMIT control fully ccw.
m. Check — that the digital voltmeter indicates a
current reading of less than 100 mA. The + CURRENT
LIMIT light should be on.
n. Turn off all power to the power module. Push and
release the PS 503A OUTPUT button and set all other
front-panel controls fully ccw .
o. This completes the Performance Check Procedure
for the PS 503A.
2-9

Section 3 — PS 503A
ADJUSTMENT
Introduction
This adjustment procedure is to be used to restore the
PS 503A to original performance specifications. Adjust 
ment need not be performed unless the instrument fails to
meet the requirements listed in the Specification section,
or the Performance Check cannot be completed satisfac 
torily.
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.
d. Install all TM 500-series equipment, including the
PS 503A into the power module.
e. Connect all test equipment to a suitable line voltage
source.
f. Turn on all test equipment and allow at least twenty
minutes for the equipment to warm-up and stabilize.
g. Set the autotransformer to the nominal line voltage
setting.
Test Equipment Required
The test equipment listed in Table 2-4 or equivalent, is
required for adjustment of the PS 503A. 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.
Initial Control Settings
Set the following controls during warm-up time:
PS 503A Dual Power Supply
- VOLTS (coarse and fine)
+ VOLTS (coarse and fine)
CURRENT LIMIT
Plus supply
Minus supply
VOLTS DUAL TRACKING
fully ccw
fully cww
fully ccw
fully ccw
pushed in and
fully ccw
Preparation
a Remove the left-hand and right-hand side covers of
the PS 503A to gain access to the component side of the
circuit boards. Pull the rear end of the side cover outward
from the side of the instrument (the cover snaps into
place).
b. Install the PS 503A into the far right (high power)
power module compartment, or if appropriate, connect
the PS 503A to the power module by means of the flexible
plug-in extender. If a flexible extender is used, current
limiting switch S95 must be engaged in the maximum
current (HI) position. See Fig. 3-1 for switch location.
c. Set the power module for the line voltage to be
applied (see power module manual) and connect it to the
autotransformer, then connect the autotransformer to the
line voltage source. Be sure that the power switch is off. ig. 3-1. Location of +20 V and — 20 V adjustment.
3-1