Tektronix PS 503A User manual

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TD D~L .LEIVCE

~S 503
®tJAL
~~

E~ SUPPL
Y
INSTRUCTION
MANUAL
Tektronix, Inc .
P .O . Box500
Beaverton, Oregon 97077

Serial Number
070-1834-01

First Printing SLPT 1974

Page
SECTION 1

OPERATING
INSTRUCTFONS

1-1
SECTION 2 , ;

SPECIFICATION AND PEFIFORMANCE CHECK

2-1
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 .

s
SECTION 3

ADJUSTMENT
SECTION 4

MAINTENANCE AND INTERFACING INFORMATION

4-1
SECTION 5

CIRCUIT DESCRIPTIpN ± .=

-

5-1
SECTION 6"

REPLACEABLE ELECTRICAL PARTS LIST

6-1
OPTIONS
'SECTION 7

DIAGRAM AND CIRCUIT BOARD
.ILI .USTRATION .

7-1
SECTION 8

REPLACEABLE MECHANICAL PARTS LIST AND
EXPLODED
VIEW

8-1
CHANGE INFORMATION
WARNING
TABLE
OF CONTENTS
PS 503A

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

INTRODUCTION

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-
Description

ting the output
of the supply .
The
PS 503A is a dual
0 to 20 V do 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-powercompartment,
it
provides a floating dual
Oto 20 Vdc at 1 .0
A . Operating in a

installation and Removal
standard
compartment of a TM
500 Series Power
Module,
the PS 503A
supplies a floating
dual 0 to 20 V do at
400 mA .

c~~
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 bo
variable-at a constant
ratio by a
common controi
Ea
, .~ .

,-- ; .-
/align `the PS503A
chassis with the upper and
lower
supply provides
dither a plus or'mir~us 0to 20
V do with

`guides of the selected
compartment . Push the module
in
respect
to the common terminal,
By connecting
across the

and press firmly to seat the
circuit board in the inter
plus and minus
terminals, the
PS503A can provide 0 to

connecting
jack .
40 V dc . Either terminal
may be grounded
or floated to
350 V (dc + peak ac) .
Each supply also features
con-
tinuously variable current
limiting from less than
50 mAto

To remove
the PS 503A, pull
on the release latch 400 mA
(standard
compartment) or 1 A (high
power
compartment)
at both 20 V
and 40 V output .

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

Controls
and Connectors
the PS 503A is operating in
a standard compartment of a
TM
500 Series Power Module and
the output current is

Refer
to
Fig . 1-3
. Even though the PS 503A
is fully
limited to a maximum
of
400
mA . Other panel-mounted,

calibrated and ready
to use, the functions and actions
of
light-emitting
diodes indicate when
either
the +
or
-

the controls and
connectors should be reviewed before
supply goes
into current-limiting . Hard limiting is in-

attempting to use it . Press the OUTPUT
button to apply
dicated by maximum brightness
of the light-emitting

power to the
PS
503A .
REV . CMAR 1977
CAUTION
Section 1-PS 503A
OPERATING
INSTRUCTIONS
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 503A, it is also
recommended that the
power
module be turned off
before removing the PS
503A .
Refer io Fig . 1-2 . . Check
to see that the plastic
barriers on
the interconnectingjack
of theselected
power module
compartment match the
cut-outs in
the PS 503A circuit board
edge connector .

OperatingInstructions-PS 503A
Load and
Monitor Connections
POWER
MODULE
~~ rrier
Improper
connections between the power-supply
out-
put and the load (s)
or monitoring devices) are
a common
cause of errors
. Multiple loadsor 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 .
Fig . 1-2 . Plug-in module
installation/removal .
Bottom
Groove
PLUG-IN
Groundedand Floating
Operation
OPERATINGCONSIDERATIONS
The PS 503A
is a + and -20 V "floating" supply
since
no internal
connections are made to either
the chassis or
Overheating

ground .
The supply can thus
be used as a positive or
The PS 503A is designed to
operate at ~n ambient

negative supply by
simply, connecting between the com-
fAmr "
Qrature from 0°G
to +5G"C . ~lowever,
when

mon and the negative
or positive uutpur terminal
.
operating
saveral power supplies in a
rpe~? ;
i-p!ug-in
pow~ . "

However, there
may bs : : :,desirable effects caused by
module, especially at low output voltages,
or when

grounding
the supply to the chassis while the load
is
operating close to other heat-producing
equipment, inter-

grounded
at some point removed
from the supply chassis .
nal temperature
may exceed safe limits and
actuate a

Forexample, if a remote load is
connected as shown in Fig,
thermal cutout
in the power module . Refer to
the power

1-5
.
ground currents containing
the power-line frequency
module instruction manual for
more complete informa-

could result and
create excessive noise and ripple in series
tion .

with the load . Thus,
floating operation is recommended to
ensure against
problems caused by undersirable
ground
currents .
ReverseCurrent
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-
REV . A MAR 1977

4p0 mA LIMIT Indicator
Light
emitting diode in-
dicates whenPS 503A is
installed in a 'standard
compartment
of a power
module,
limiting the
current output .
VOLTS
Controls
and
Indicators
Variable
coarse and tine
controls
provide con-
tinuously
variable + or-
voltage election
from the
respective 0-20
voli
supply
The presence
and
variability
of output
voltage is
verified 'by
voltage indicalor
lights
(OUTPUT
button
pressed) . Brightness
of
lights
varies with output
voltage :
REV .
B
MAR
1977
Floating Output
Terminals
Fig . 1-3 .

PS 503A controls and
connectors .
5-way binding post ter-
minals that provide either
a positive 0-20- volts
between
the binding post
on
the right (red) and
t :OMMON,
or a negative
t)-20 volts between the
binding past on the left
(green) and COMMON .
When the
PS503A is in-
stalled in he high
power
compartment of aTM
504
or TM 506 power module
that
has a high ; power
compartment, tt e current
available
at either the r or
- outputs is from less
than `
100 mA to at least
1 A : When the
PS 503A is
compartment, the
current

Output Terminals
available is from ess than
100 mA `to

at `least

5-way binding-posttermi-
400 mA . 0 to 4Q volt out-

nals

that

provide

a
put
s'obtained' between

ground-referenced +5 V,
the +
and - output ter-

1 A, fixed output .
urinals .
Operating
Instructions-PS 503A
VOLTS DUAL
TRACKING Control
When pulled
out, vanes
both the'-1-'and
- outputs
from 0 volts to he value
set on the + and - VOLTS
controls
.' The - ratio be-
tween
the+and-outputs
is maintained
throughout
the range
of the VOLTS
DUALTRACKING 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 .
installed in a
standard _
1834-05

OperatingInstructions-PS 503A
NOTE
Supply is
connected for 20 to 40 V output .
Over-voltage
POWER
SUPPLY
AC
VOLT
+
METER
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 .
The PS 503A is protected from over-voltageconditions
by an over-voltage protection circuit
that shuts down the
power
supply
when the voltage rises to about 26 V dc .
POWER I

I ACTIVE
SUPPLY

LOAD
Rs
NOTE
Supply is
connected
for
0 to 40 V output .
Fig,
t-4 . Monitor and load connections .

Fig .
1-4 . Reversr current shunt
(Rs)
with active load .
NOTE
The point at which the overvoltage protection blows
the fuse
may be changed forspeclfic applications by
changing the Zener diode .
OPERATION
The following steps demonstrate the use of the
PS503A 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
PS503A .Observethatthe+and-VOLTSindicatoriights
come on (the lights will be very dim at low voltages) ._
Single
Supply Operation (t20 V Maximum)
1 . Set the + and - VOLTS controls for approximately
2 V .
2 . Turn the CURRENT
LIMIT
controls
fully ccw (to
NOTE

protect the
ammeter) . Connect an ammeter between the
supply is connected for o to ao v output .

common terminal and the + or - terminal and adjust the
appropriate CURRENT LIMIT control for the maximum

)
Fig . 1-5 . Ground loop
created by grounded remote lead .

desired current
output .
REV . A MAR 1977

3 . Removethe ammeter . Connect the
load between the

Stair-Step Operation
common
terminal and the+or-terminal .
Adjust the+or

The PS 503A can be operated
to provide a "stair-step"
,~

- VOLTS
control for the desired output .

output characteristic by choosing certain load limits
and
control settings . Forexample, Fig .1-7showsthestair-step
output
from the
PS 503A when a variable load (RL) is
connected between the +
and - output terminals . With
each supply set for maximum
voltage and current (40 V,
y

1 A) theoutput voltage remains constant
from open circuit
Combined
Supply Operation (40 V
Maximum)

~

until the
load reachesapproximately 40 S2 as illustrated by
1 .

Set the + and - VOLTS control
for approximately

the solid line in Fig . 1-7 .
At this crossover point, theoutput
j

2 V and turn the
CURRENT LIMIT controls fully
ccw
(to

voltage decreases with the load
and the output current is
protect the
ammeter) .

limited at 1 A . Therefore,
below approximately 40 S2, both
supplies act as current sources with
output voltage
variable with the load . Since both supplies are set for the
'

2 .
Connect an ammeter
between the + and - ter-

same output voltage,
each supply shares equally in the
urinals . First
adjust one CURRENT LIMIT
control for the

Power output

I Z R . If one supply
is set for a lower output
maximum desired current
output ; then adjust the other

voltage than the other, output power
is shared at the same
CURRENT LIMIT control
until the CURRENT LIMIT

ratio as the output voltage .
indicator just reaches maximum
brightness, i .e ., both
1

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 togetherequal thedesired output
voltage . (See Dual-Tracking
Operation for varying the
output with the VOLTS DUAL
TRACKING control .)
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 a2 V
change in the 20 V
output (2 :1 ratio)
.

ao
Note also that no matter where
the VOLTS DUAL

I

w
j
30
TRACKING control is set, the
outputs will return to the

~

1
voltage
selected by the + and - VOLTS
control when the

~

20
0
VOLTS DUAL
TRACKING control is pushed in .
Therefore,

>
rapid selection of two
preset outputs from each supply is

~

10
achieved by merely switching the
VOLTS DUAL

w
TRACKING
control in or out .
REV
. B MAR 1977
Now, by setting
supplyEzforacurrentlimitof0 .5 Aand
varying the load
over the same range, the supplies act as
constant-voltage sources until
the load reaches ap-
proximately 80 S2 . At that crossover point,
the supply set
for 0 .5 A
(Ez)
becomes a current source and
its output
OperatingInstructions-PS
503A
!
o
9
0
When the +and
- supplies are connected as described

I ~

Is
under Combined Supply
Operation, the VOLTS DUAL

CURRENT IN AMPERES
TRACKING control will
vary the output from zero to the
value
selected by the + and -
VOLTS controls added

Fig . 1-7 . Output characteristics with
various currents, voltages,
together .

and loads .

OperatingInstructions-PS
503A
voltage
decreases with the
load . At approximately
40
f2

Parallel-Connected
Supplies
and
20 V, supply
Ez
no longer
contributes to the power
output .
Subsequently, supply E,
supplies all the output

"""'
power and
operates as a constant-voltage
source with

CAUTION
output current
variable with the load . Then,
at ap-
proximately 20 f2, supply
E, crosses over and becomes
a

Parallel
operation is not recommended
unless a
current
source at its maximum
output of 1 A . Thus, by

forward biased
diode capable of handling
the re-
choosing
the appropriate load limits
and control settings,

quired current and voltage
is inserted between
each
any of the four
operating characteristics
is possible .

power supply and the
load . Failure to do this may
cause power supply damage .
A
second stair-step output can
be preselected and
switched
in or out with the VOLTS
DUAL TRACKING

The outputs of two or
more PS 503's can be
connected
control (see
Dual-Tracking Operation
for details on the

in parallel as shown in Fig . 1-9
to obtain an output current
function of the
VOLTS DUAL TRACKING
control) .

equal to the sum of theoutput
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) .
One supply should
be set for the desired output
voltage
NOTE

and the other for a slightly
higher voltage . The supply
set
forthe desired voltage will then
become a constant voltage
The PS 503A has internal
diodes connected across

source, while the
supply with the
higher voltage output
the
output to protect the
series-connected supplies

becomes a
current source (due to
automatic crossover),
against reverse
polarity if the load is
shorted, or one

which results
in their output voltage
decreasing to that of
of the supplies is
not on .

the supply with the
lowest output voltage .
POWER I

I
POWER
SUPPLY

SUPPLY
LOAD
NOTE
Each supply is connected for 0 to 80 V output .
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 .
POWER

POWER
SUPPLY
I

I
SUPPLY
NOTE
Each supply is connected
for 0 to 2A output .
Fig . 1-8 . Supplies
series-connected .

Fig . 1-9 . Supplies
parallel-connected .
REV . B MAR 1977