Crown PB-3 Service manual

Power Base-3 & 1400CSL Amplifier Service Manual

POWER AMPLIFIER

SERVICE MANUAL

POWER BASE ™-3 & 1400CSL

©1995 by CROWN INTERNATIONAL, INC.

Mailing Address:

P.O. Box 1000

Elkhart, IN U.S.A. 46515-1000

Shipping Address:

57620 C.R. 105

Elkhart, IN U.S.A. 46517

™

CSL™ and Power Base™ are trademarks, and ODEP® and Crown® are registered trademarks of Crown International, Inc.

K-SVCPB3

6-95

1

Power Base-3 & 1400CSL Amplifier Service Manual

The information furnished in this manual does not include all of the details of design, production, or variations
of the equipment. Nor does it cover every possible situation which may arise during installation, operation or
maintenance. If you need special assistance beyond the scope of this manual, please contact the Crown
Technical Support Group.

Mail: P.O. Box 1000 Elkhart IN 46515-1000

Shipping: 57620 C.R. 105 Elkhart IN 46517

Phone: [phone]

FAX: [phone]

CAUTION

TO PREVENT ELECTRIC SHOCK DO

NOT REMOVE TOP OR BOTTOM
COVERS. NO USER SERVICEABLE
PARTS INSIDE. REFER SERVICING

TO QUALIFIED SERVICE

PERSONNEL. DISCONNECT

POWER CORD BEFORE REMOVING

REAR INPUT MODULE TO ACCESS

GAIN SWITCH.

WARNING

TO REDUCE THE RISK OF ELECTRIC

SHOCK, DO NOT EXPOSE THIS

EQUIPMENT TO RAIN OR MOISTURE!

AVIS

À PRÉVENIR LE CHOC

ÉLECTRIQUE N’ENLEVEZ

PAS LES COUVERTURES.

RIEN DES PARTIES

UTILES À L’INTÉRIEUR.

DÉBRANCHER LA BORNE

AVANT D’OUVRIR LA

MODULE EN ARRIÈRE.

2

Power Base-3 & 1400CSL Amplifier Service Manual

Table of Contents

Introduction .............................................................4

Scope......................................................................4

Warranty..................................................................4

Parts Information ..................................................... 5

Specifications..........................................................6

Voltage Conversion ................................................. 7

Circuit Theory .......................................................... 8

Electrical Checkout Procedures............................13

Parts List (Non-Module) ........................................ 16

Module Information ...............................................19

Q43339-3 Output Module .....................................20

Q43353-4 Main Module (Original).........................21

Q43400-3 Main Module.........................................24

3

Power Base-3 & 1400CSL Amplifier Service Manual

Introduction

This manual contains service information on Crown
power amplifiers. It is designed to be used in conjunc­tion with the applicable Owner's Manual. However,
some important information is duplicated in this Ser­vice Manual in case the Owner's Manual is not readily
available.

NOTE: THE INFORMATION IN THIS MANUAL IS INTENDED
FOR USE BY AN EXPERIENCED TECHNICIAN ONLY!

SCOPE

This Service Manual includes several sections. These
sections include Parts Ordering, Specifications, Volt­age Conversion, Circuit Theory, Factory Test Proce­dures, Mechanical Parts Lists, and Module Parts Lists.
Schematics are attached. Note that component parts
with circuit board comprise a complete module. Mod­ule part numbers are always associated with a spe­cific circuit board, although an unpopulated circuit
board may be built up with different parts to create
different modules. Note that Crown does not sell blank
(unpopulated) circuit boards.

Each of the compact audio power amplifiers are
designed for professional or commercial use. Provid­ing high power amplification from 20Hz to 20KHz with
minimum distortion, they feature balanced inputs with
bridged and parallel monophonic capability. Specific
features vary depending on model family.

WARRANTY

Each Owner's Manual contains basic policies as re­lated to the customer. In addition it should be stated
that this service documentation is meant to be used
only by properly trained service personnel. Because
most Crown products carry a 3 Year Full Warranty
(including round trip shipping within the United States),
all warranty service should be referred to the Crown
Factory or Authorized Warranty Service Center. See
the applicable Owner’s Manual for warranty details. To
find the location of the nearest Authorized Service
Center or obtain instructions for receiving Crown Fac­tory Service please contact the Crown Technical Sup­port Group (within North America) or your Crown/
Amcron Importer (outside North America).

Crown

Technical Support Group

Factory Service

Parts Department

Mailing Address:

PO Box 1000

Elkhart, IN USA 46515-1000

Shipping Address:

57620 C.R. 105

Elkhart, IN USA 46517

Phone: [phone]

Toll Free: [phone]

FAX: [phone]

4

Power Base-3 & 1400CSL Amplifier Service Manual

Parts Information

GENERAL INFORMATION

Later sections include both mechanical and electrical
parts lists for this product. The parts listed are current
as of the date printed. Crown reserves the right to
modify and improve its products for the benefit of its
customers.

PART NUMBERING SYSTEMS

As of the printing of this manual, Crown is using two
numbering systems. The elder system always uses
eight characters. The first character is a letter. Com­mon letters used are C, D, H, M, P, and Q. The second
through sixth characters are numbers. The numbers
build sequentially (for each prefix letter) as new parts
are added to our parts inventory system. (In some
cases there will be a space then a four character
number after the prefix letter; the space is considered
a character.) The seventh character is usually a hy­phen, though it may be a letter to indicate a revision or
special note. The last character is called a check-digit,
and is useful to Crown for internal tracking.

Crown is in the process of converting to a new part
number system. Length may vary from eight to twelve
characters. There is still a letter prefix, then five
numbers. These five numbers identify a type of part.
The seventh character is a hyphen. Remaining char­acters identify the details of the type of part identified
by the first part of the number.

STANDARD AND SPECIAL PARTS

Many smaller electrical and electronic parts used by
Crown are stocked by and available from electronic
supply houses. However, some electronic parts that
appear to be standard are actually special. A part
ordered from Crown will assure an acceptable re­placement. Structural items such as modules and
panels are available from Crown only.

shipment on a C.O.D. or pre-payment (check or credit
card) basis.

TERMS

Normal terms are pre-paid. Net-30 Days applies to
only those firms having pre-established accounts with
Crown. If pre-paying, the order must be packed and
weighed before a total bill can be established, after
which an amount due will be issued and shipment
made upon receipt of pre-payment. New parts re­turned for credit are subject to a 10% re-stocking fee,
and authorization from the Crown Parts Department
must be obtained before returning parts for credit.

Crown is not a general parts warehouse. Parts sold by
the Crown Parts Department are solely for servicing
Crown/Amcron products. Part prices and availabil-

ity are subject to change without notice.

Crown

Parts Department

Mailing Address:

PO Box 1000

Elkhart, IN USA 46515-1000

Shipping Address:

57620 C.R. 105

Elkhart, IN USA 46517

ORDERING PARTS

When ordering parts, be sure to give the product
model, and include a description and part number
(CPN/DPN) from the parts listing. Price quotes are
available on request.

SHIPMENT

Shipment will be normally made by UPS or best other
method unless you specify otherwise. Shipments are
made to and from Elkhart, Indiana USA, only. Estab­lished accounts with Crown will receive shipment
freight prepaid and will be billed. All others will receive

Phone: [phone]

or: [phone]

Toll Free: [phone]

FAX: [phone]

5

Power Base-3 & 1400CSL Amplifier Service Manual

Specifications

Unless noted otherwise, all specifications are based
on driving an 8 ohm load per channel, both channels
driven, the sensitivity switch in the 26dB position, the
AC supply is 120VAC at 60Hz. Crown specifications
are guaranteed through the warranty period (normally
3 years). Because our testing methods are more strin­gent than our published specifications, every Crown
amplifier will exceed its published specifications.

POWER

Power

8 Ohm Stereo—500W/Ch
4 Ohm Stereo—700W/Ch
8 Ohm Bridge Mono—1500W
4 Ohm Parallel Mono—1050W
2 Ohm Parallel Mono—1515W

Load Impedances: Rated for 16, 8, 4, and 2 (parallel
mono only) Ohm operation; safe with all types of loads,
even totally reactive loads.

AC Mains: 120VAC at 60 Hz with standard 3 wire
grounded 15A connector with single voltage trans­former and fan for North American units; 100VAC,
120VAC, 220VAC, and 240VAC at 50 or 60 Hz when
equipped with universal transformer, applicable fan,
and other applicable hardware with country specific
power cord. Note that at 50 Hz fan speed is reduced.

PERFORMANCE

Frequency Response: ±0.1dB from 20 Hz to 20 kHz at 1

Watt.

Phase Response: ±10° from 10 Hz to 20 kHz at 1 Watt.
Signal to Noise Ratio: A-weighted, better than 105 dB

below full rated output. Better than 100 dB below full
rated output from 20 Hz to 20 kHz.

Total Harmonic Distortion (THD): <0.05% from 20 Hz to
1 kHz, increasing linearly to 0.1% at 20 kHz at 500W.

I.M. Distortion: <0.05% from 170 milliwatts to 500 W at
26 dB gain.

Slew Rate: >13V per microsecond.
Damping Factor: >1000 from 10 Hz to 400 Hz.

Input Impedance: Nominally 20K ohms balanced; 10K

ohms unbalanced.
Output Impedance: <10 milliohms in series with <2

microhenries.
Protection Systems: Output Device Emulation Protec-

tion (ODEP) limits drive in the event of dangerous
dynamic thermal conditions without interrupting power.
Current limiting for shorted load protection. DC/LF and
common mode output current Fault circuitry to mute
audio. Delay of 4 seconds from turn on mutes amplifier
to prevent dangerous turn-on transients. High voltage
circuit breaker in main transformer primary and low
voltage fuse in fan primary. Slew rate limiting to
prevent RF burn out.

MECHANICAL

Input Connectors: Balanced 1/4 inch phone jacks. Op-

tional XLR inputs with MT-XLR accessory.
Output Connectors: Color-coded 5-way binding posts

on 3/4 inch centers; spaced 3/4 inch apart.

Front Panel Controls: A rocker on/off power switch.
Back Panel Controls: A three-position switch which

selects Stereo, Bridge-Mono, or Parallel-Mono mode;
a two position input ground-lift switch, and level con­trols for each channel.

Internal Controls: A three-position switch selects 0.775V,

1.4V, or 26 dB voltage gain input sensitivity.
Indicators: Red Enable indicator shows on/off status of

low-voltage power supply.
Construction: Black splatter-coat steel chassis with

specially designed flow-through ventilation system.
Mounting: Standard EIA 310 front-panel rack mount

with supports for supplemental rear corner mounting.
Dimensions: 19 inches wide, 3.5 inches high, 16 inches

deep behind front mounting surface.

Weight: 36 lbs. Shipping; 40 lbs.

DC Offset: <10 millivolts.

6

Power Base-3 & 1400CSL Amplifier Service Manual

Voltage Conversion

PB/CSL Universal Fuse Board

BLU

BRN

P19

P20

P10

P9

P8

P7

P16

P15

P14

P13

P12

P11

P6

P5

P4

P3

P2

P1

P22

100V Connections:
P10 to P15
P11 to P14
P7 to P12

120V Connections:
P10 to P16
P11 to P14
P7 to P13

220V Connections:
P10 to P15
P9 to P14
P8 to P13

240V Connections:
P10 to P16
P9 to P14
P8 to P13

For list of applicable
transformer, fuse F100,
fanformer, and power
cord refer to voltage­parts cross-reference.

F1F100

P18

S1 Power Switch

P17

Note: The only versions of this
product produced at the Crown
Factory with international volt­age capabilities are the CSL
versions built specifically for
sale outside the United States.

P21

Specific parts are required for the PB-3/1400CSL in
order to be used at different international line volt­ages. Refer also to Mechanical Parts Lists.

Voltage Specific Parts:
30A Breaker for 100-120V Operation C 9837-3
15A Breaker for 220-240V Operation C 9839-9

0.5A F1, Low Voltage* A10285-7
Power Transformer (United States) D 8598-1
Power Transformer (Universal) D 8601-3
Transmotor 120V 60 Hz Only H43065-4
Transmotor 120V 50-60 Hz H43055-5

*Use 0.3A for UL® approval A10285-33

7

Power Base-3 & 1400CSL Amplifier Service Manual

Theory

OVERVIEW

It should be noted from the outset that the PB-3 and
1400CSL amplifiers are electrically and mechanically
identical products. The only differences, from a ser­vice perspective, are cosmetic. It should also be
noted that over time Crown makes improvements and
changes for various reasons. This manual is up to date
as of the time of writing. For additional information
regarding these amplifiers, refer to the applicable
Technical Notes provided by Crown for this product.

This section of the manual explains the general opera­tion of a typical Crown power amplifier. Topics cov­ered include Front End, Grounded Bridge, and ODEP.
Due to variations in design from vintage to vintage
(and similarities with other Crown products) the theory
of operation remains simplified.

FEATURES

Power Base/CSL amplifiers utilize numerous Crown
innovations including grounded bridge and ODEP
technologies. Cooling techniques make use of the
what is essentially air conditioner technology. Air flows
bottom to top, and front to side. Air flows a short
distance across a wide heatsink. This type of air flow
provides significantly better cooling than the “wind
tunnel” technology used by many other manufactur­ers. Output transistors are of the metal can type rather
than plastic case. This allows for a significantly higher
thermal margin for the given voltage and current
ratings. All devices used are tested and graded to
ensure maximum reliability. Another electronic tech­nique used is negative feedback. Almost all power
amplifiers utilize negative feedback to control gain
and provide stability, but Crown uses multiple nested
feedback loops for maximum stability and greatly
improved damping. Most Crown amplifiers have damp­ing in excess of 1000 in the bass frequency range. This
feedback, along with our compensation and ultra-low
distortion output topology, make Crown amplifiers
superior.

Features specific to the Power Base/CSL Series’ in­clude a single core transformer (one primary with two
independent ungrounded secondaries), a full time full
speed fan which also serves as the low voltage
transformer, slew rate limiting, and audio muting for
delay or protective action. This amplifier can operate
in either a Bridged or Parallel Mono mode as well as
dual (stereo). A sensitivity switch allows selection of
input voltage required for rated output. Level controls
are rear mounted. The only indicator provided tells the

operator that the low voltage supply is energized. In
general, the packaging of this model is designed for
maximum watt/price/weight/size value. It is the most
basic grounded bridge amplifier series now available
from Crown.

For additional details refer to the specification section,
or to the applicable Owner’s Manual.

FRONT END OPERATION

The front end is comprised of three stages: Balanced
Gain Stage (BGS), Variable Gain Stage (VGS), and
the Error Amp. Figure 1 shows a simplified diagram of
a typical front end with voltage amplification stages.

Balanced Gain Stage (BGS)

Input to the amplifier is balanced. The shield may be
isolated from chassis ground by an RC network to
interrupt ground loops via the Ground Lift Switch. The
non-inverting (hot) side of the balanced input is fed to
the non-inverting input of the first op-amp stage. The
inverting (negative) side of the balanced input is fed
to the inverting input of the first op-amp stage. A
potentiometer is provided for common mode rejection
adjustment. Electrically, the BGS is at unity gain.
(From an audio perspective, however, this stage
actually provides +6dB gain if a fully balanced signal
is placed on its input.) The BGS is a non-inverting
stage. It’s output is delivered to the Variable Gain
Stage.

Variable Gain Stage (VGS)

From the output of the BGS, the signal goes to the VGS
where gain is determined by the position of the Sen­sitivity Switch, and level is determined by the level
control. VGS is an inverting stage with the input being
fed to its op-amp stage. Because gain after this stage
is fixed at 26dB (factor of 20), greater amplifier sensi­tivity is achieved by controlling the ratio of feedback to
input resistance. The Sensitivity Switch sets the input
impedance to this stage and varies the gain such that
the overall amplifier gain is 26 dB, or is adjusted
appropriately for 0.775V or 1.4V input to attain rated
output.

Error Amp

The inverted output from the VGS is fed to the non­inverting input of the Error Amp op-amp stage through
an AC coupling capacitor and input resistor. Amplifier
output is fed back via the negative feedback (NFb)
loop resistor. The ratio of feedback resistor to input
resistor fixes gain from the Error Amp input to the

8

Power Base-3 & 1400CSL Amplifier Service Manual

Theory

output of the amplifier at 26 dB. Diodes prevent
overdriving the Error Amp. Because the Error Amp
amplifies the difference between input and output
signals, any difference in the two waveforms will
produce a near open loop gain condition which in turn
results in high peak output voltage. The output of the
Error Amp, called the Error Signal (ES) drives the
Voltage Translators.

VOLTAGE AMPLIFICATION

The Voltage Translator stage separates the output of
the Error Amp into balanced positive and negative
drive voltages for the Last Voltage Amplifiers (LVAs),
translating the signal from ground referenced ±15V to
±Vcc reference. LVAs provide the main voltage ampli­fication and drive the High Side output stages. Gain
from Voltage Translator input to amplifier output is a
factor of 25.2.

Voltage Translators

A voltage divider network splits the Error Signal (ES)
into positive and negative drive signals for the bal­anced voltage translator stage. These offset reference
voltages drive the input to the Voltage Translator
transistors. A nested NFb loop from the output of the
amplifier mixes with the inverted signal riding on the
offset references. This negative feedback fixes gain at
the offset reference points (and the output of the Error
Amp) at a factor of -25.2 with respect to the amplifier
output. The Voltage Translators are arranged in a
common base configuration for non-inverting voltage
gain with equal gain. They shift the audio from the
±15V reference to VCC reference. Their outputs drive
their respective LVA.

Also tied into the Voltage Translator inputs are ODEP
limiting transistors and control/protection transistors.
The ODEP transistors steal drive as dictated by the
ODEP circuitry (discussed later). The control/protec­tion transistors act as switches to totally shunt audio to
ground during the turn-on delay, or during a DC/LF or
Fault protective action.

Last Voltage Amplifiers (LVAs)

The Voltage Translator stage channels the signal to
the Last Voltage Amplifiers (LVA's) in a balanced
configuration. The +LVA and -LVA, with their push-pull
effect through the Bias Servo, drive the fully comple­mentary output stage. The LVAs are configured as
common emitter amplifiers. This configuration pro­vides sufficient voltage gain and inverts the audio. The
polarity inversion is necessary to avoid an overall
polarity inversion from input jack to output jack, and it
allows the NFb loop to control Error Amp gain by
feeding back to its non-inverting input (with its polarity
opposite to the output of the VGS). With the added
voltage swing provided by the LVAs, the signal then
gains current amplification through the Darlington
emitter-follower output stage.

GROUNDED BRIDGE TOPOLOGY

Figure 2 is a simplified example of the grounded
bridge output topology. It consists of four quadrants
of three deep Darlington (composite) emitter-follower
stages per channel: one NPN and one PNP on the
High Side of the bridge (driving the load), and one
NPN and one PNP on the Low Side of the bridge
(controlling the ground reference for the rails). The
output stages are biased to operate class AB+B for

Audio

Inputs

BGS VGS Error

Amp

+

-

+

-

+

-

Figure 1. Typical Amplifier Front End and Voltage Amplification Stages.

+15V

Voltage Divider

+

-15V

-

ODEP

Q100

Q103

Mute

Q121

Q122

NFb Loop

Voltage

Translators

Q101

Q102

+VCC

Q105

NPN Outputs (+HS)
PNP Outputs (-HS)

Q110

-VCC

LVA's

9