RTS PS-31 User manual

User Manual
MODEL PS-31
Power Supply
POWER
THERMAL
OVERLOAD
321
FAULT
AUDIBLE
ALERT
ON
CHANNEL STATUS
PROGRAM
LEVEL
CHANNEL
ASSIGN
1
2
3
TW INTERCOM SYSTEM
POWER SUPPLY
PS31
RTS SYSTEMS
9300-4437-00 Rev H 06/2005

PROPRIETARY NOTICE
The product information and design disclosed herein were
originated by and are the property of Telex Communications, Inc.
Telex reserves all patent, proprietary design, manufacturing,
reproduction, use and sales rights thereto, and to any article
disclosed therein, except to the extent rights are expressly granted to
others.
COPYRIGHT NOTICE
Copyright 2005 by Telex Communications, Inc. All rights reserved.
Reproduction, in whole or in part, without prior written permission
from Telex is prohibited.
WARRANTY NOTICE
See the enclosed warranty card for further details.
CUSTOMER SUPPORT
Technical questions should be directed to:
Customer Service Department
Telex Communications, Inc.
12000 Portland Avenue South
Burnsville, MN 55337 U.S.A.
Telephone: [phone]
Fax: [phone]
RETURN SHIPPING INSTRUCTIONS PROCEDURE
FOR RETURNS
If a repair is necessary, contact the dealer where this unit was
purchased. If repair through the dealer is not possible, obtain a
RETURN AUTHORIZATION from:
Customer Service Department
Telex Communications, Inc.
Telephone: [phone]
Fax: [phone]
DO NOT RETURN ANY EQUIPMENT DIRECTLY TO THE
FACTORY WITHOUT FIRST OBTAINING A RETURN
AUTHORIZATION.
Be prepared to provide the company name, address, phone number,
a person to contact regarding the repair, the type and quantity of
equipment, a description of the problem and the serial number(s).
SHIPPING TO THE MANUFACTURER
All shipments of product should be made via UPS Ground or best
available shipper, prepaid. Any shipment upgrades will be paid by
the customer. The equipment should be shipped in the original
packing carton. If the original carton is not available, use any
suitable container that is rigid and of adequate size. If a substitute
container is used, the equipment should be wrapped in paper and
surrounded with at least four inches of excelsior or similar shock-
absorbing material. All shipments must be sent to the following
address and must include a Return Authorization.
Factory Service Department
Telex Communications, Inc.
1930 West 1st Street
Blue Earth, MN 56013 U. S. A.
Attn.: Service
Upon completion of any repair, the equipment will be returned via
United Parcel Service or specified shipper, collect.

TABLE OF CONTENTS
CHAPTER 1
DESCRIPTION 1
1.1 Description ......................................................................................................................................1
1.1.1 General ..........................................................................................................................1
1.1.2 Features ..........................................................................................................................1
1.2 Installation ......................................................................................................................................3
1.2.1 Mechanical Installation .................................................................................................3
1.3 Electrical Installation ......................................................................................................................3
1.3.1 Connecting Intercom Stations .......................................................................................3
1.3.2 Using Two Ps31's To Expand Capacity .........................................................................4
1.3.3 Program Inputs ..............................................................................................................4
1.3.4 Ac Power .......................................................................................................................4
CHAPTER 2
OPERATION 7
2.1 Power-up Indications .......................................................................................................................7
2.2 Fault Indications ..............................................................................................................................7
2.3 Thermal Overload ...........................................................................................................................8
2.4 Impedance Select Switches .............................................................................................................8
2.5 Program Input ..................................................................................................................................8
CHAPTER 3
THEORY OF OPERATION 9
3.1 General ............................................................................................................................................9
3.2 Ac To Dc Conversion ......................................................................................................................9
3.3 Impedance Generator ....................................................................................................................10
3.4 Program Insertion Amplifier .........................................................................................................10
3.5 Display And Diagnostic Circuitry .................................................................................................11
3.5.1 Channel Status Indicators ............................................................................................11
3.5.2 Fault Indicator .............................................................................................................11
3.5.3 Thermal Overload ........................................................................................................11

2
CHAPTER 4
MAINTENANCE 13
4.1 Introduction ...................................................................................................................................13
4.2 General Maintenance ....................................................................................................................13
4.2.1 Safety Considerations ..................................................................................................13
4.2.2 Access ..........................................................................................................................14
4.2.3 Cleaning ......................................................................................................................14
4.2.4 Input Power Selection .................................................................................................14
4.2.5 Channel Dc Output Fuse Replacement .......................................................................15
4.3 Test Procedures .............................................................................................................................15
4.3.1 Test Equipment ............................................................................................................15
4.3.2 Initial Inspection ..........................................................................................................15
4.3.3 Power-up Test ..............................................................................................................15
4.3.4 Powered Channel Test .................................................................................................16
4.3.5 Functional Test Of All Outputs ...................................................................................17
4.4 Troubleshooting ............................................................................................................................19
CHAPTER 5
REPLACEMENT PARTS 21
5.1 Where To Obtain Parts ..................................................................................................................21
5.2 Mechanical Parts ...........................................................................................................................22
5.3 Electrical Parts .............................................................................................................................23
CHAPTER 6
DIAGRAMS and SPECIFICATIONS 29
Specifications ......................................................................................................................................31

1
1.1 DESCRIPTION
CHAPTER 1
DESCRIPTION
1.1 DESCRIPTION
1.1.1 GENERAL
The Model PS31 supplies 32 volts regulated DC power to each of three intercom channels. It has short circuit
and thermal overload protection, with automatic recovery when the fault is removed.
1.1.2 FEATURES
Program Input
There is a PROGRAM INPUT connector on the rear panel. A CHANNEL ASSIGN switch on the front panel
assigns the program to any of the three channels. A LEVEL control adjusts the program level to the intercom
channel.

DESCRIPTION
2
Status Indicators
There is an audible alarm and a red FAULT indicator for current overload indication on any of the three channels.
An AUDIBLE ALERT switch on the front panel turns the alarm on or off, but the FAULT indicator will continue
to flash during current overload conditions. There is also a green status indicator for each channel. Each of these
indicators will remain lit during normal operation, but will turn off during a channel current overload condition.
Output current is automatically reduced during an overload, and normal operation is restored when the overload
is removed.
Input Power
The PS31 is available in two versions: one for 115 VAC operation and one for 230 VAC operation. A simple
internal modification changes the operating voltage for 100 VAC or 200 VAC. A POWER on/off switch is pro-
vided on the front panel.
Figure 1. PS-31 Front and Back View
TELEX COMMUNICATIONS, INC.
MADE IN USA
TW INTERCOM SYSTEM
POWER SUPPLY
MODEL PS 31
NOTE
INTERNALLY
FUSED
CONNECTOR
PIN-OUT CODE
CH1-2
PIN - 1 COM
PIN - 2 CH 1
PIN - 3 CH 2
CH1-3
PIN - 1 COM
PIN - 2 CH 1
PIN - 3 CH 3
CH2-3
PIN - 1 COM
PIN-2 CH2
PIN-3 CH3
CH1-2-3
PIN - 1
PIN-2 CH2
PIN-3 CH3
PIN - 4 COM
CH 1
OUTPUTS CONNECT TO
TW INTERCOM SYSTEM COMPONENTS
REFER TO OPERATION MANUAL
OUTPUTS
IMPEDANCE SELECT
CHANNEL
CH 1-2-3 CH 1-2-3 CH 1-2-3
PUSH
12 3
J107 J108 J109
J110
J111
AC POWER
J101 J102 J103 J104 J105 J106
CH 2-3CH 2-3CH 1-3CH 1-3CH 1-2CH 1-2
PROGRAM INPUT
Z = 10K BALANCED
PIN 1 - GROUNDED
PIN 2 - LO
PIN3-HI
400
DUAL
200
NORM
W
W
CAUTION
WARNING
- TO REDUCE THE RISK OF FIRE, REPLACE ONLY WITH SAME TYPE FUSE
- TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK, DO NOT EXPOSE THIS APPLIANCE TO RAIN OR MOISTURE
POWER
THERMAL
OVERLOAD
321
FAULT
AUDIBLE
ALERT
ON
CHANNEL STATUS
PROGRAM
LEVEL
CHANNEL
ASSIGN
1
2
3
TW INTERCOM SYSTEM
POWER SUPPLY
PS31
RTS SYSTEMS

3
1.2 Installation
Intercom Channel Connections
Intercom channels are connected to the rear panel of the PS31. A variety of connector pin-outs is provided to
accommodate individual system requirements.
Impedance Selection
The PS31 provides the required channel terminating impedance for each channel. A 200/400 ohm IMPEDANCE
SELECT switch for each channel is located on the rear panel. These switches are set to 200 ohms for normal
operation. The 400 ohm setting permits two PS31's to be coupled to double the DC capacity of the system.
1.2 Installation
1.2.1 MECHANICAL INSTALLATION
The Model PS31 can be rack mounted or used free standing. The rack mount is a standard 19-inches wide by 3.5-
inches high. Allow room for cable connections.
1.3 ELECTRICAL INSTALLATION
1.3.1 CONNECTING INTERCOM STATIONS
NOTE: When connecting intercom stations, do not exceed the power supply capacity, either for one channel
or for all three channels. Power supply capacity is graphically illustrated in Figure 1. If more capacity
is required, refer to “PS 31 Capacity” on page 5.
Connect intercom channels to the OUTPUTS connectors on the rear panel. Pin assignments are printed above the
connectors. These connectors provide three alternatives for intercom channel connection:
•Connectors J101 through J106 can be used to connect various combinations of two channels.
•Connectors J107 and J108 can be used to connect all three channels.
•Connector J109 can also be used to connect three channels, but unlike all the other connectors, no power
is supplied at this connector. This connector can be used to interconnect the audio channels when using
two PS31 power supplies.

DESCRIPTION
4
1.3.2 USING TWO PS31'S TO EXPAND CAPACITY
If there are more stations on one or more channels than the power supply capacity will allow, two PS31 power
supplies may be used to double capacity. For each channel that requires added capacity:
1. Use the J109 connectors on both power supplies to interconnect the audio and ground pins of the desired
channel (See “PS-31 Front and Back View” on page 2.).
2. Divide the stations that you wish to connect into two groups. Connect one group to the first power supply.
Connect the other group to the second power supply. For each group, do not exceed the capacity (either
total or per channel) of the power supply.
3. On both power supplies, set the IMPEDANCE SELECT switches for the channel to the
400<F128M>W<F255D> DUAL position. (Leave all impedance switches for channels that are not inter-
connected in the 200<F128M>W<F255D> NORM position.
1.3.3 PROGRAM INPUTS
A program source may be connected to the PROGRAM INPUT connector on the rear panel. Pin assignments are
printed above the connector (See “PS-31 Front and Back View” on page 2.).
To connect an unbalanced program source, connect pin 2 to to pin 1. Then connect program ground to pin 1 and
program HI to pin 3.
If two PS31's are interconnected, a separate program source may be connected to each.
1.3.4 AC POWER
Plug the AC power cord into the PS31 and into an AC mains outlet.
NOTE: The PS31 is factory-set for either 110-120-volt operation or 220-240-volt operation. The operating
voltage is indicated on the back of the unit. Operation at 100-110 volts or 200-220 volts requires an
internal modification. Refer to “MAINTENANCE” on page 13.

5
1.2 Installation
Figure 2. PS 31 Capacity

DESCRIPTION
6

7
2.1 POWER-UP INDICATIONS
CHAPTER 2
OPERATION
2.1 POWER-UP INDICATIONS
Turn on the POWER switch. During normal operation the three CHANNEL STATUS indicators should be lit
and the FAULT and THERMAL OVERLOAD indicators should be off.
2.2 FAULT INDICATIONS
If there is a fault on a channel, the CHANNEL STATUS indicator for that channel will turn off and the red
FAULT indicator will flash. If the AUDIBLE ALERT is set to “ON”, the alarm will beep. Possible causes of a
fault include: overvoltage, overcurrent, short circuit to ground or severe brown-outs.

OPERATION
8
2.3 THERMAL OVERLOAD
If the PS31 overheats, the THERMAL OVERLOAD indicator will turn on and AC power to the PS31 will be
shut off. Normal operation will resume when the PS31 cools. Possible causes of a thermal shut-down include
overloading the output channels or improper internal mains voltage selection.
2.4 IMPEDANCE SELECT SWITCHES
The IMPEDANCE SELECT switches on the rear panel allow each channel to be set for 200 ohm or 400 ohm
operation. Select 200<F128M>W<F255D> NORM for each channel operated independently. Select
400<F128M>W<F255D> DUAL for each channel connected to another channel through the AUDIO ONLY
connector (J109). Figure 1, “PS-31 Front and Back View,” on page 2
2.5 PROGRAM INPUT
If a program source is connected to the PROGRAM INPUT connector on the back of the PS31, it may be routed
to any one of the intercom channels using the CHANNEL ASSIGN switch. Use the LEVEL control to adjust the
program level on the selected channel.

9
3.1 GENERAL
CHAPTER 3
THEORY OF OPERATION
3.1 GENERAL
The PS31 electronic circuits include an AC to DC converter, an impedance generator for each channel, a
program insertion amplifier, and display and diagnostics circuits (Figure 3 on page 12). The following
paragraphs describe these circuits. For schematic reference, see drawing SD3225 in Chapter 7.
3.2 AC TO DC CONVERSION
Transformer T101 steps down the AC mains voltage to 33 volts rms. Diodes D101-D104 rectify this voltage and
capacitor C117 filters out the AC component, leaving about 45-50 volts unregulated DC. This raw DC voltage
feeds the impedance generators (through fuses F201, F301, and F401), and regulator U101.
U101 provides regulated 30 volts DC. This voltage is supplied to the impedance generators, to the program
insertion amplifier, and to U102. Diodes D109 and D110 protect U101. Resistors R107 and R108 establish the
output voltage reference of 30 volts DC. Capacitor C121 reduces the amount of ripple on the 30 volts DC, and
C122 provides decoupling.

THEORY OF OPERATION
10
U102 provides regulated 7.5 volts DC. This voltage is used as a reference level by the program insertion
amplifier. It also powers the display circuits. Diodes D111 and D112 protect U102. Resistors R109 and R110
establish the output voltage reference of 7.5 volts. Capacitor C123 reduces the amount of ripple on the 7.5 volts
DC and C124 filters the output.
3.3 IMPEDANCE GENERATOR
There is a separate impedance generator for each channel. The impedance generator supplies regulated 32 volts
DC to the channel and also provides the channel terminating impedance. The following paragraphs describe the
impedance generator for channel 1. Other channels are identical.
Diodes D202 and D201 and resistors R202 and R201 divide the raw DC for the variable DC reference. This
variable DC reference allows the quiescent output voltage of the regulators to follow the rms value of the AC
mains voltage. Capacitors C202, C203 and C204 and resistors R203 and R206 are a low pass filter for the
variable DC reference and provide fast start up response time. Integrated circuit U202B, resistors R214, R215
and R217 and capacitors C210 and C207 amplify and buffer the variable DC reference. Resistor R213 and
capacitor C209 decouple the supply voltage for integrated circuit U202. Resistors R211 and R208 set the amount
by which the output voltage of the regulator exceeds the variable DC reference. R205 sinks the quiescent current
from R208. Diode D203 clamps excessive output voltage of the regulator due to transients while diodes D204
and D206 protect the regulator from reversed voltages due to shorts on the output line.
Resistors R219 and R221 sense the output current from the regulators into the RTS line. Integrated circuit
U202A, together with capacitors C212 and C214 and resistors R220, R225, R223, and R216 differentially
amplify this output current and feed it back to the adjust terminal of the regulators to create the audio impedance.
Diodes D207, D208, D211, D212, D209, and D210 clamp the audio output voltage to avoid over-driving the RTS
line and allow fast recovery from large transients.
Diode D214 protects the impedance generator from an over voltage on the RTS line. Capacitor C215 is an RF
bypass and resistor R227 biases diode D214 on with 10 mA of current for “dry line” operation. Toggle switch
S201, located on the rear panel selects an output impedance of 200 or 400 ohms. Since the impedance generator
operates at 400 ohms, toggle switch S201 shunts the output with 390 ohms for a 200 ohm output.
3.4 PROGRAM INSERTION AMPLIFIER
The program-insertion amplifier circuitry accepts balanced or unbalanced input from any source and injects this
input, via a bilateral current source, onto the RTS line.

11
3.5 DISPLAY AND DIAGNOSTIC CIRCUITRY
Program audio, present at connector J110, rear panel, is applied via input isolation transformer T103 to
PROGRAM LEVEL potentiometer R111. Resistor R606 and capacitor C601 provide RF suppression. Integrated
circuit U601a, capacitor C602 and resistors R603 and R602 amplify the input and provide a low impedance drive
for the following stage. Integrated circuit U601b, capacitor C606 and resistors R604, R607, R609, R605, and
R608 form the bilateral current source which turns the input voltage into an output current. Capacitors C604,
C605 and resistor R610 blocks any DC potential on the RTS line. Diodes D601 and D602 protect integrated
circuit U601 from transients and resistor R601 and capacitor C603 decouple the power to integrated circuit
U601.
3.5 DISPLAY AND DIAGNOSTIC CIRCUITRY
The display and diagnostic circuits detect fault conditions and warn the user with front panel lights and an audio
indicator.
3.5.1 CHANNEL STATUS INDICATORS
(The channel status indicator for channel is described. The channel status indicators for channels 2 and 3 are
identical.)
As long as the output voltage on channel 1 is above approximately 21 VDC, diode D205 will conduct causing
transistor Q201 to be on, which turns on DS201, the CHANNEL 1 STATUS LED on the front panel. If the
channel 1 voltage drops below approximately 21 volts, transistor Q201 shuts off, LED DS201 goes dark, and the
fault indicator circuitry is notified through diode D215.
3.5.2 FAULT INDICATOR
If pin 5 of integrated circuit U103 is driven high by an under-voltage condition on any channel, the flasher
circuit, which consists of half of integrated circuit U103, capacitor C126 and resistors R116 and R117, will flash
the FAULT indicator LED, DS101, and pulse the audible alarm circuit. The audible alarm oscillator consists of
the other half of integrated circuit U103, capacitor C127 and resistors R120 and R121.
3.5.3 THERMAL OVERLOAD
Switch S101 is a thermal sensing switch connected in series with the power switch. It is attached to the power
transformer, T101. The front panel THERMAL OVERLOAD indicator, DS5, is connected across S101. If the
transformer temperature remains below approximately 75 C, S101 will remain closed, and there will be no

THEORY OF OPERATION
12
voltage drop across DS5. If the transformer temperature rises above 75 C, S101 will open and remove AC
primary power to T101. The AC voltage will be developed across DS5 and it will light.
Figure 3. Block Diagram

13
4.1 INTRODUCTION
CHAPTER 4
MAINTENANCE
4.1 INTRODUCTION
This section provides service information for normal maintenance, factory performance tests and
troubleshooting tips.
4.2 GENERAL MAINTENANCE
4.2.1 SAFETY CONSIDERATIONS
Service and adjustments should be performed only by qualified service personnel.
Any adjustment, maintenance, and repair of the opened equipment while any power or voltage is applied should
be avoided as much as possible, and should be carried out only by a skilled person who is aware of the hazard
involved.

MAINTENANCE
14
It is possible for capacitors inside the equipment to still be charged even if the equipment has been disconnected
from its power source.
Be certain that only fuses with the required current rating and of the specified type (fast blow, time delay, slow
blow, etc.) are used for replacement. The use of repaired fuses and the short-circuiting of fuse holders must be
avoided.
4.2.2 ACCESS
To get inside the Model PS31, remove the screws on the top and bottom covers. Slide covers off toward the back
of the unit.
4.2.3 CLEANING
Clean the outside of the Model PS31 with denatured alcohol or a mild solution of detergent and water. Clean the
interior with dry, low pressure air. The circuit boards can be cleaned with 1,1,1 trichloroethane or Freon TF. Do
not allow these or any solvents to get into any potentiometers.
4.2.4 INPUT POWER SELECTION
CAUTION: These maintenance instructions are for qualified personnel only. To avoid electric shock, do not
perform any servicing unless qualified to do so. Disconnect AC power before servicing.The Model PS31
operates on 100, 120, 200, or 240 volts AC at 50/60 hertz, depending on the internal power settings. To convert
from one mains voltage to another, remove the covers and set the internal switch, jumpers and use the proper rear
panel fuse as specified in Table 3. (The switch and jumpers are located on the circuit board next to the power
transformer connector.)
TABLE 4. Voltage Selection
AC Source S107 Setting Jumpers Rear
Panel
Fuse
Add Remove
100 VAC 115 W2, W3 W1, W4 3A
120 VAC 115 W1, W4 W2, W3 3A
200 VAC 230 W2, W3 W1, W4 1.5A
240 VAC 230 W1, W4 W2, W3 1.5A

15
4.3 TEST PROCEDURES
4.2.5 CHANNEL DC OUTPUT FUSE REPLACEMENT
To replace channel fuses (F201, F301, F401), remove covers. These fuses are located on the circuit board.
4.3 TEST PROCEDURES
4.3.1 TEST EQUIPMENT
•An isolated, variable voltage power transformer with voltage and current metering ("VARIAC",
"POWERSTAT", or equivalent)
•A sine wave oscillator
•An oscilloscope, 15 megahertz minimum bandwidth
•A distortion analyzer (HP331 through HP334, HP339, or equivalent)
•An AC voltmeter capable of reading volts, dBm and dBu
•Two DC voltmeters
•A test load (see Figure 4)
•A capacitive load box (see Figure 5)
•A program input cable (see Figure 6)
•Two channel output cables (see Figure 7)
4.3.2 INITIAL INSPECTION
Verify electrical orientation of power supply capacitors. Verify proper wiring of transformer primary for local
mains voltage. Verify that the proper fuses are installed in the back panel fuse holder and on the printed circuit
board. Check that the transformer is securely mounted and that it is electrically isolated from the chassis
(resistance from chassis to transformer core should be greater than 10 kohms). Check that the power supply
capacitor is securely fastened. Using an ohmmeter, verify that the chassis is electrically connected to the
grounding pin on the power connector (less than 0.2 ohm).
4.3.3 POWER-UP TEST
1. Set the variable voltage power transformer to off, and set the voltage to zero.
2. Plug the PS31 into the variable voltage power transformer.
3. Set the PS31 POWER switch to ON.

MAINTENANCE
16
4. Set the PS31 AUDIBLE ALERT switch to ON.
5. Turn on the variable voltage power transformer.
6. Slowly turn up the voltage. Watch for excessive sustained current consumption above 1 ampere.
While the voltage is being increased, the audible alert indicator should sound and the FAULT light
should flash. Stop increasing the voltage when the standard operating voltage level is reached.
7. Set the AUDIBLE ALERT switch to off.
8. Turn the PS31 POWER switch off: the STATUS lights should fade, and finally, the FAULT light
should blink. The audible alert should not sound.
9. Turn the POWER switch back on.
10. Turn the AUDIBLE ALERT switch on.
4.3.4 POWERED CHANNEL TEST
The following procedure tests channel 1. Repeat for channels 2 and 3.
1. Connect the DC meters and capacitive load to the test load as shown in Figure 5-1.
2. Set the capacitive load to OFF.
3. On the test load, set the output current potentiometer in the fully CCW position (minimum output
load).
4. Plug one of the four-wire channel output cables into J108 on the PS31. This will be the powered
output cable
5. Connect the ground lead of the powered output cable to the test load ground terminal.
6. Connect channel 1 of the powered output cable to the powered channel terminal of the test load.
7. Connect the second four-wire output cable to J109 on the PS31. This will be the AUDIO ONLY
output cable.
8. Connect channel 1 and ground of the audio only output cable to the distortion analyzer input and
to the AC voltmeter.
9. Connect the program input cable to the PS31 PROGRAM INPUT (J110) and to the sine wave
oscillator.
10. On the PS31, set the PROGRAM CHANNEL ASSIGN switch to channel 1. Turn the PS31
PROGRAM LEVEL control fully CCW (minimum level).
11. Set the sine wave oscillator for 1 kilohertz, 0.10 volt rms at the PROGRAM INPUT of the PS31.
12. Observe the DC output voltage on DC voltmeter 1. It should be between 31.0 and 32.5 volts DC.
13. Set the output current adjustment control on the test load so that the output current is 0.50
amperes (0.5 volts at DC voltmeter 2). The output voltage at voltmeter 1 should drop by 0.5 volts
or less.