Rauland Dax60 Manual

DAX60

60-WATT

POWER AMPLIFIER

DAX120

120-WATT

POWER AMPLIFIER

INSTALLATION AND SERVICE

KI-1480

RAULAND-BORG

CORPORATION

3450

West

Oakton

Street, Skokie, Illinois 60076-2951

(708)

679-0900

GENERAL DESCRIPTION

The Rauland DAK Series amplifiers are designed for use with Rauland's

institutional program and communication systems. They offer high-quality sound

and dependability. They can be driven to their rated power output by an input

signal as low as

0.3

volts.

Their transformer-isolated, 25-volt balanced out-

put matches the output of Rauland's communication panels; they also have a

70.7-volt

balanced output.

Their outputs can operate with a split center tap

with Rauland's

Telecenter®

5000 and Responder@ 3000 systems.

The amplifiers

are listed by Underwriters Laboratories,

The DAX amplifiers offer helpful power connections for related equipment:

three

120-VAC

three-pin grounded outlets,

and a floating auxiliary DC power

output (28 VDC, 1.2 A) that can be used for Rauland's Director Series control

panels, preamplifiers, graphic equalizer, and other equipment.

The amplifiers come with black-enamel face panels.

Optional

brushed-

chrome dress panels--

the RP2525

(DAX6O)

and RP2700

(DAX120)--are

available.

UNPACKING

The amplifier was thoroughly checked at the factory. Inspect the amplifi-

er,

the enclosed parts,

and the shipping container for signs of improper han-

dling during shipment. In case of damage,immediately place a claim: with the

dealer or distributor from whom you purchased the unit or--if the unit was

shipped directly to you--with the carrier.

The following parts are included with the amplifier:

Description

Qty.

Rauland

Part No.

Rack-Mounting Screws for tapped holes

(l0-32

½"

hex-head,

WA202

SEMS, unslotted, machine).

Rack-Mounting Screws for untapped holes (10 x

½"

pan-head,

WA102

slotted,

thread-forming).

#l0

Tinnerman

"U"

type Speed Nuts, for untapped rack holes.

AB1889

INSTALLATION

The amplifier should be rack-mounted where there is adequate ventilation,

a moderate temperature, an AC power outlet,and provisions for grounding.

The rack should have the standard

19-inch

width and a vertical space of at

least

5¼

inches

(DAX6O)

or 7 inches (DAX120). It is recommended that

addition-

01987 RAULAND-BORG CORPORATION

PRINTED IN U.S.A.

7/87

Page 1 of 17

al space be left above and below the amplifier to prevent hum from being intro-

duced into adjacent equipment (such as preamplifiers), to provide additional

ventilation,and to allow easier access for servicing. Adding an inch of space

behind the amplifier for connections,the rack should have a total depth of

seven inches. A cooling fan is recommended when the rack is enclosed and any

of the following conditions obtains:

(a) The combined rated output power of all the equipment exceeds 250 watts

RMS; OR

(b) The

input

from the AC power line exceeds 500 watts; OR

heat.

CAUTION

FAILURE TO OBSERVE THE PRECEDING PRECAUTIONS COULD RESULT IN OVERHEATING

THAT COULD DAMAGE THE EQUIPMENT OR CREATE A FIRE HAZARD.

Rack-Mounting

The DAK Series amplifiers are designed to be mounted into a standard

19-

inch rack.

#lO

"U"

nuts (AB1889) and two kinds of mounting screws are supplied

with each amplifier.

A. If the rack's holes are untapped,

select the

#10

thread-forming screws

(WA102).

Push the

#l0

"U"

nuts,

their flat side facing

proper holes in the rack (you may have to leave the

"U"

holes are extruded).

outward,

onto the

nuts off if the

B. If the rack's holes are tapped, select the

#10

machine

screws

(WA202).

Turret-Mounting

(DAX60

only)

The rack-mounting procedures can be used to install the

Control Turret. However,if the turret's internal rails are DAX60 in a Rauland

used and the am-

plifier is oriented with its front panel facing the rear of the

turret,

optional

MKlO

Mounting Kit will be needed. This special-order kit must be

installed by the factory.

WARNING

DO NOT CONNECT AC POWER TO THE AMPLIFIER UNTIL ALL OF THE NECESSARY INPUT

AND OUTPUT CONNECTIONS HAVE BEEN COMPLETED.

Page 2

7/87

Grounding

CAUTION

DO NOT DISCONNECT THE THIRD WIRE ON THE POWER PLUG. THIS WIRE GROUNDS THE

AMPLIFIER'S CHASSIS TO PREVENT A POSSIBLE SHOCK HAZARD. IF AN ADAPTER IS

USED TO CONNECT THE PLUG TO A TWO-PRONG SOCKET, MAKE SURE THAT THE AMPLI-

FIER'S CHASSIS IS CONNECTED TO A PROVEN EARTH GROUND.

INPUT CONNECTIONS

The input is unbalanced.

The input screw terminals are labeled

"COM"

(-)

and "INPUT"

(+),

respectively.

The terminal strip is located on the lower

right corner, as viewed from the rear of the chassis. The signal source should

deliver at least 300 millivolts into a 13-kilohm load.

Route the input cables as far from the speaker cables as possible, to

prevent coupling.

OUTPUT CONNECTIONS

The output screw terminals are located on the upper right corner, as

viewed from the rear of the chassis. The following illustration shows how the

output transformer's split windings are connected with a factory-installed link

for most applications (for applications with the link removed, see "Split-Cen-

ter-Tap Operation," below).

70.7V

(Link)

25V

CT CT 25V 70.7 v

VOLTAGE TAPS OF THE DAX SERIES AMPLIFIERS

IL0252

The output impedances are

DAX6O:

70.7V

= 83.3

DAX120:

70.7V

= 41.6

as follows:

ohms;

25V

10.4 ohms.

ohms;

25V

5.2 ohms.

Page

7/87

Selecting Balanced or Unbalanced Output Connections

The balanced outputs for 70.7 volts and 25 volts are for speakers designed

for constant-voltage lines. Each speaker must have a line-matching transform-

er,

and the speakers must be connected in parallel. The impedance taps on the

primaries of the line-matching transformers indicate how much power will be

taken from the line. Speakers can be added as required until the total wattage

absorbed by all of the transformers is equal to the rated power output of the

amplifier.

However,it is good practice to allow an amplifier a headroom of

10% to 20%.

For a 60-watt amplifier,the maximum speaker load should be ap-

proximately 50 watts; for a 120-watt amplifier,the maximum speaker load should

be approximately 100 watts.

For unbalanced operation, place a jumper between one of the speaker termi-

nals you are using and

"GND."

Do not ground the center tap when you use unbal-

anced operation.

Grounding the Center Tap

If required by the installation,

the center-tap terminals may be

jumpered

to the

"GND"

terminal when the BALANCED speaker output is used.

The

"GND"

terminal is next to the negative

"AUX POWER" terminal on the

DAX60;

on the

DAX120, the

"GND"

terminal is next to the

"COM"

input terminal.

When the two

center-tap terminals are linked together,either one of them may be connected

to the

"GND"

terminal.

DO NOT INSTALL A JUMPER BETWEEN "GROUND" AND "CT" WITH THE UNBALANCED

SPEAKER CONNECTION: CONNECTING BOTH POINTS TO "GROUND" WOULD CREATE A

SHORT CIRCUIT ACROSS THE OUTPUT TRANSFORMER.

Split-Center-Tap Operation

The amplifier output transformer can be configured for split-center-tap

operation with symmetrical output voltages on both sides of the center tap.

This is intended for special applications with Rauland systems such as the

Telecenter 5000 and the Responder 3000.

When a

DAX

amplifier is used with the

TC5000 or the NCS3000, (a) no more than 50 watts of power may be drawn through

the system, and

(b)

a TC5007 Transformer Module is required (see KI-1486).

If the installation requires an isolated, split-center-tapped output,

remove the supplied link from the two "CT" terminals: this will separate the

two halves of the output windings (see "OUTPUT CONNECTIONS," above,. and the

attached

KMO780).

Note: There is a large capacitor inside the TC5000 and the NCS3000 that

provides a low AC impedance across the center taps. The split windings

are not designed to be used independently.

Auxiliary DC Power Supply

The 28-VDC terminals (on the right side of the DAX60, below the output

transformer of the DAX120) can provide up to 1.2 Amperes to preamplifiers,

Director Series control panels,and other auxiliary devices requiring DC power.

Since this supply is floating,

it can also be used for devices requiring an

7/87

Page 5

isolated power source, such as Rauland's Model 6430Pink-Noise Source and Model

6431

l/3-Octave

Equalizer. Do not mix floating and

grounded accessories.

POWER CONNECTION

Plug the power cord into a

120-V,

60-HZ, three-wire grounded outlet that

can provide at least 935 watts

(DAX6O)

or 1105 watts (DAX120). Although the

amplifier circuits by themselves consume no more than 175 watts (DAX60) or 345

watts

(DAX120),

connecting another device to the DC output could consume anoth-

er 40 watts of power,and a total load of 720 watts could be connected to the

three AC sockets. Check the local regulations before installing permanent AC

lines and plugging in the equipment.

Converting the Amplifiers to 240 VAC

If operation from a 240-VAC power source is desired, remove the front

cover and locate the

"12OV/240V"

switch inside the amplifier, on the right.

Use a small screwdriver to slide the switch to the

"24OV"

side.

Resecure the

front cover. Replace the fuse with a fast-blow, 240-volt fuse with half the

current rating of the supplied fuse;the new value would be 1.25 Amps for the

DAX60, 2.5 Amps for the DAX120 (see "REPLACING THE FUSE," below). Replace the

plug on the power cord with one approved for 240-VAC operation.

CAUTION: When the amplifier is connected to a 240-volt supply, its three

"120

VAC"

convenience outlets will supply 240 volts. Accordingly, they

should not be used when the amplifier is connected to 240 volts.

SETTING THE "INPUT LEVEL" CONTROL

The input-level control,

marked "LEVEL" on the rear chassis below the out-

put transformer (see Figure

l),

can be adjusted with a

¼-inch

flat-blade screw-

driver:

turning the control clockwise will increase the output level. This

control should be set so that the maximum possible input signal will not cause

the output to clip.

After this control has been adjusted by the installer, it

should be left alone.

REPLACING THE FUSE

A current surge during operation may cause the fuse to blow. To restore

power to the amplifier, first ascertain what the problem is and correct it

before replacing the fuse. Use a fast-blow fuse: 2.5 Amps for the DAX60,

5 Amps for the

DAX120

(but only half of these values if the amplifier is oper-

ating from a 240-VAC line).

The fuse holder is on the rear of the amplifier, below the power trans-

former.

You will need a Phillips screwdriver to remove the center plug; you

may find a scissors-nosed pliers helpful in removing the fuse. If the replace-

ment fuses continue to blow, unplug the amplifier and consult a qualified ser-

vice representative.

Page 6

7/87

INITIAL TROUBLESHOOTING

Problem

1) Low volume or

distorted sound.

2) The amplifier does

not operate.

3) The 28-VDC output

cycles off and on,

or it remains off.

Possible Causes

(a)

(b)

(a)

(b)

(c)

(a)

(b)

Check whether all the input and output connections

are properly made and securely fastened.

If the sound is distorted, check whether the speak-

ers are being overdriven (e.g., does the distortion

go away when the level control is turned down?).

Make sure that the power cord is plugged in and

that there is power in the outlet.

Examine the input and output lines for (1) obvious

shorts (among themselves and between them and the

chassis or surrounding equipment) and (2) broken

connections.

If everything appears in order, try replacing the

fuse.

If the amplifier still fails to respond,

unplug the power cord and contact your local

Rauland distributor.

There are two circuit breakers protecting this

output.

CB2 is a 1.6-Amp thermal breaker that

shuts down the circuit when the DC

current

flow

significantly exceeds the output's

1.2-Ampere

rat-

ing,

then automatically resets. It will continue

cycling off and on until the problem is corrected.

If the amplifier remains off,

CBl

(3.15 Amps) may

have tripped. Check for a short in the connec-

tions,

then try manually resetting

CBl

by poking a

small screwdriver through the access hole in the

front cover (at the upper left corner of the

DAX6O,

or the lower left corner of the DAX120)).

If the problem does not lie in the load or the

connections,one of the breakers may be defective.

Disconnect the load and call your Rauland distribu-

tor.

7/87

Page 7

SERVICING INFORMATION

THE INFORMATION THAT FOLLOWS IS INTENDED FOR QUALIFIED SERVICE TECHNICIANS.

Locating the Test Points

Whenever possible,take the voltage readings on the large connector on the

main printed circuit board. You will have to remove the front cover to access

it.

The DAX60 has a single 16-pin connector labeled

"T"

on the schematic; the

pins are numbered from bottom to top on the board.

The DAX120 has two 16-pin connectors: the top connector and the top half

of the bottom connector are referred to as

"Jl"

on the schematic, and the rest

of the bottom connector is referred to as

"J2"

on the schematic.

The pins are

numbered l-24 and l-8, from top to bottom on the board.

Measuring DC

Voltages

DC voltages are printed in rectangular boxes at various points on the

schematic.

When measuring these voltages on the amplifier, use a DC meter with

a resistance of 1

megohm

per volt and proceed as follows:

Step 1.

Place the amplifier on a suitable work surface and make sure that no

signal is present at the input terminals.

Disconnect the speakers and con-

nect a suitable resistive load in their place:

DAX6O:

The load should have at least a 60-watt power rating and a value of

10.4 ohms across the 25-volt output or 83.3 ohms across the

70.7-volt

output).

DAX120: The load should have at least a

120-watt

power rating and a value of

5.2 ohms across the 25-volt output or 41.6 ohms across the

70.7-volt

output).

Step 2. Plug the amplifier into a 120-VAC, 60-HZ source.

Step 3. On the

DAX6O:

Connect the meter's negative lead to the amplifier common

at Connector "T-14."

As you locate each DC voltage on the schematic,.note

the number of the nearest

"T"

terminal in that leg of the circuit and, if

possible,

take the readings between such a

"T"

terminal and "T-14."

On the DAX120: Connect the meter's negative lead to the amplifier common at

Connector

"J1-13."

As you locate each DC voltage on the schematic, note the

number of the nearest

"J"

terminal in that leg of the circuit and, if possi-

ble, take the readings between such a

"J"

terminal and

"J1-13."

Measuring AC Voltages

AC voltages are printed without boxes at various points on the schematic.

When measuring these voltages on the amplifier, use an AC meter with a

one-

megohm

impedance and proceed as follows:

Page 8

7/87

Step 1.

Place the amplifier on a suitable work surface. Disconnect the speak-

ers and replace them with a suitable resistive load:

DAX6O:

The load should have at least a 60-watt power rating and a value of

10.4 ohms across the 25-volt output (or 83.3 ohms across the

70.7-volt

output).

DAX120: The load should have at least a 120-watt power rating and a value of

5.2 ohms across the 25-volt output or (41.6 ohms across the

70.7-volt

output).

Step 2. Disconnect any input device and connect a one-kilohertz signal source

in its place.

The source should be able to provide an amplitude of approxi-

mately 300 millivolts. Leave its output level turned down.

Step 3. Plug the amplifier into a 120-VAC, 60-HZ source. Turn the input-level

control fully clockwise, for maximum gain.

Step 4. Connect the test leads across the 25-V or 70.7-V outputs. Slowly in-

crease the output from the l-KHz signal source until you obtain the rated

output voltage from the DAK. Check the input level required to obtain the

rated output:

a reading of 300 millivolts or less is an indication that the

amplifier gain is functioning properly.

Step 5. On the

DAX6O:

Connect the meter's negative lead to the amplifier common

at Connector "T-14."

As you locate each AC voltage on the schematic, note

the number of the nearest

"T"

terminal in that leg of the circuit and, if

possible,

take the readings between such a

"T"

terminal and "T-14."

On the DAX120: Connect the meter's negative lead to the amplifier common at

Connector

"J1-13."

As you locate each AC voltage on the schematic, note the

number of the nearest

"J"

terminal in that leg of the circuit and, if possi-

ble, take the readings between such a

"J"

terminal and

"J1-13."

Locating the Driver and Power Transistors

On both amplifiers, driver transistors

Q505

and

Q506

are screwed to the

"L"

bracket that is fastened to the large heat sink from inside the chassis.

The power transistors

(Q507-Q508

on the

DAX60,

Q5Ol-Q504

on the

DAX120)

are

fastened directly to the large heat sink from the outside (to access them,

remove the protective cover). The transistors are numbered in ascending order,

with the lowest number at the bottom.

Removing and Replacing Transistors

Transistors are inherently long-lived devices that normally should not

need replacement. If, however,systematic troubleshooting indicates a problem,

observe these precautions when removing and replacing transistors:

(1) Transistors can be damaged by excessive heat,

so use a small soldering

iron when removing or replacing a transistor with solder connections.

(2) Transistors come with a wide variety of cases and leads. To avoid a cost-

ly mistake,

make a careful sketch of the lead connections before removing

a transistor from a printed circuit board or tie points.

7/87

Page 9

(3) Before installing a power transistor

(Q507-Q508

on the DAX60,

Q5Ol-Q504

the

DAX120),

obtain an appropriate

Silpad

insulator. If a mica insulator

is used instead, coat both sides of it with silicone grease (Dow-Corning

DC4 or an equivalent). Fit the insulator between the transistor and the

heat sink, as shown below.

Heat sink

with socket

attached 7

M3 silicone grease or equivalent.

LTO-3

case transistor IL0253

After installing a power transistor, check for a short circuit:

Step 1. On the DAX120, isolate the circuit common from the chassis by discon-

necting the wire between the negative side of

C503

(the large electrolytic

capacitor nearest the auxiliary

120-VAC

outlets) and the star connector at

the right end of the amplifier (as viewed from the front). This capacitor

is not grounded to the chassis in the DAX60.

Step

2. Use

an ohmmeter to check for a short between the transistor case and

the heat sink. If there is a low-resistance reading, check the insulator,

the screws, etc.,as possible causes.

Step

After obtaining a high-resistance reading (at least 100 kilohms) be-

tween each transistor case and the heat sink, re-establish the connection

between the negative side of

C503

and the star connector (DAX120 only).

Testing Transistors

The best way to test a transistor is to use

transistor tester.

However,

if one is not available, use an ohmmeter.

Most failures result in a short or

an open circuit between the collector and the emitter.

Connect the ohmmeter's leads to the collector and the emitter, then use

the low ohm range

read the resistance.

If the reading in this range remains

the same when the leads are reversed, the transistor is shorted. If the read-

ings are"infinite" for both connections, the transistor is open.

Page 10

7/87

DAX60

Circuit Description

Refer to the attached schematic,KC1546, to trace the circuit descriptions

that follow.

Input and Preamplifier Circuits:

Resistor

and Capacitors Cl and

C507

reject Radio Frequency Interference (RFI).

RVl

is the input LEVEL control

(potentiometer),

which controls the signal level that is applied to the

DAX's

preamplifier circuits. Capacitors C2 and C8 govern the low-frequency response

of the input signal,to protect horn-type speakers.

Transistor

is a common-

emitter amplifier that provides the preamplifier gain. It is also a common-

base

invertor

for the feedback entering its emitter.

Power-Amplifier Circuits: Transistor

is a high-voltage-gain amplifier

that drives Transistors

and

Q4.

The latter are phase splitters that form a

unity-gain configuration.

Diode D503 is a negative-temperature-coefficient

device mounted on the heat sink.

This diode controls the DC bias for the drive

and the output transistors.

Transistors

Q505

and

Q506

are current amplifiers

(drivers) that supply high base current to the output transistors, 4507 and

Q508.

The latter are push-pull power amplifiers that drive the output trans-

former.

Capacitor

C506

blocks DC from the output transformer and limits the

low-frequency output to protect horn-type speakers.

Protective Circuits: There are several protections against excessive cur-

rent.

Resistors R16 and

R19

are current limiters; if a short occurs across the

audio output, each resistor will drop 10 VDC.

An excessive current surge will

cause the fuse to open. In the 28-VDC supply,a short circuit on the DC output

or a DC load that draws significantly more current than 1.2 Amperes will cause

Thermal Breaker CB2 to open within 70 seconds. It will try to reset within 15

seconds,

then continue opening and closing until the short or the excessive

load is removed, at which time it will remain closed for normal operation. A

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