Soundcraft CPS 250, CPS275 USER GUIDE

CPS 250
CPS 275

USER AND

TECHNICAL MANUAL

SOUNDCRAFT CPS250

CPS275

Console Power Supply

User and Technical Manual

For your own safety and to avoid invalidation of the
warranty all text marked with these Warning
Symbols should be read carefully.

IMPORTANT: please read this manual carefully
before connecting your Soundcraft console power
supply to the mains for the first time.

© Harman International Industries Ltd. 1997, 2001
All rights reserved

Parts of the design of this product may be protected by worldwide patents.

Part No. ZM0 1 95 Issue 4
Soundcraft is a trading division of Harman International Industries Ltd.
Information in this manual is subject to change without notice and does not

represent a commi tment on the part of the vendor. Soundcraft shall not be liable for
any loss or damage whatsoever arising from the use of information or any error
contained in this manual, or through any mis-operation or fault in hardware
contained in the p roduct.

No part of this manual may be reproduced, stored in a retrieval system, or
transmitted, in any form or by any means, electronic, electrical, mechanical, optical,
chemical, including photocopying and record ing, for any purpose without the
express written permission of Soundcraft.

It is recommended that all maintenance and service on the product should be
carried out by Soundcraft or its authorised agents. Soundcraft cannot acce pt any
liability whatsoever for any loss or damage caused by service, maintenance or
repair by unauthorised personnel.

Harman International Industries Ltd.
Cranborne House
Cranborne Industrial Estate
Cranborne R oad
Potters Bar
Herts.
EN6 3JN
England

Tel: [phone]
Fax: [phone]

Table of Contents

Introduction 1

Introduction 2
Short-circuit Protection 2
Mains Voltage Selection 3
Replacing Mains Fuse 3
Warranty 4

Recommendations For Installation 5

Recommendations For Installation 6
General 7
Dimensions 8
PSU Linking (CPS275 Only) 8

Technical Specification 9

Technical Description 11

Circuit Diagram (1) 12
Circuit Diagram (2) 13
Circuit Description 14
Servicing 17
PCB Layout 20
Output Pinouts 21

Parts List 23

i

ii

Introduction

Introduction 1

Introduction

WARNING: THIS APPARATUS MUST BE EARTHED

The CPS250/CPS275 are linear power supplies which, like other linear supplies,
produce DC voltages by rectifying, smoothing and regulating AC voltages from the
secondary windings of a mains transformer. Soundcraft mixing consoles employ a
number of dc voltage supply levels in their op eration and these are all provide d at the
output of each supply unit.

The CPS275 provides higher currents than the CPS250. The CPS275 also has the
capability of being linked to a second CPS275 to provide a utomatic power backup in
the event of one of the units failing.

In regulating these voltages there is considerable heat generated, the dissipation of
which is achieved through a substan tial internal heat sink. A fan is incorporated which
draws air over the heatsinks to provide adequate heat dissipation for the regulators
and reduce the outer case tempera ture .

The CPS250/CPS275 is designed for installation in a 19" rack unit, oc cupyin g 2U of
rack height. Refer to the section "RECOMMENDATIONS FOR INSTALLATION"
on Page 5.

LED indication is provided on the front panel to show operation of the regulating
circuits.

SHORT-CIRCUIT PROTECTION

The +/-17V rails can withstand a short to ground or each other for up to one second;
if the short circuit remains for longer than one second then both of the 17V ra ils will
be shut down. To reset them the supply must be switched off for 6 seconds and then
switched on again.

The +5V and +48V are current limited and will self rec over whe n any short ci rcuit is
removed.

2 Introduction

MAINS VOLTAGE SELECTION

Special attention should be paid to the fo llowing infor m atio n:

Do not change the voltage setting without first
turning the unit off and unplugging the mains lead.

This unit is capable of operating over a range of mains voltages by means of a
4-position mains input fuse carrier. It is important to ensure that the correct voltage
setting is selected for the level of local mains voltage supply, for safe, uninterrupted
operation of the unit. Voltage selection is achieved by positioning the fuse carrier so
that the required voltage appears next to the arro w which is moulded in the conne ctor.
In this way the unit is set up for operation at one of the following ranges of mains
supply:

NOMINAL VOLTAGE OPERATING VOLTAGE RANGE

(+10/-15%)

Vrms AC Vrms AC

230 196 - 253
115 98 - 126
100 85 - 110
85 73 - 93

To remove the fuse use a small screwdriver to prise the fuse carrier from its location
in the connector.

To avoid risk of fire use the correct value fuse, as
indicated on the unit.

REPLACING MAINS FUSE

Switch the ON/OFF switch to the OFF position. Remove the mains lead from the
connector. Use a small screwdriver to prise th e fuse carrier from its location i n the
connector. Check the fuse and replace if necessary; also check that the voltage
selection is correct for the mains supply level be fore switc hin g the unit ON agai n.

In the event of repeated failure of t he mains fuse co nsult the Sound craft dealer from
where the unit was purchased.

This unit contains no user serviceable parts. Refer
all servicing to a qualified service engineer, through
the appropriate Soundcraft dealer.

Introduction 3

Warranty

1

Soundcraft
End User
Dealer

purchased the Equipment, provided such a pe rs on is a utho ri se d fo r th is purpos e by
Soundcraft or its accredited Distributor.

Equipment

2 If within the period of twelve months from the date of delivery of the Equipment
to the End User it shall prove defective by reaso n only of faul ty ma terials and/or
workmanship to such an extent that the effectiveness and/or usability thereof is
materially affected the Equipment or the defe c tiv e c omp onent should be returned
to the Dealer or to Soundcraft and subject to the following conditions the Dealer or
Soundcraft will repair or replace the defective com pon en ts. Any com pone nt s
replaced will become the property of Soundcraft.

3 Any Equipment or component returned will be at the risk of the End User whilst
in transit (both to and from the Dealer or Soundcraft) and postage must be prep ai d.

4 This warranty shall only be available if:

a) the Equipment has been properly installed in accordance with instructions

contained in Soundcraft’s manual; and

is a trading division of Harman International Industrie s Lt d.

means the person who first puts the equipment into regular operati on.

means the person other than Soundcraft (if any) from whom the End User

means the equipment supplied with this ma nua l.

b) the End User has notified Soundcraft or the Dealer within 14 da ys of the defe ct

appearing; and

c) no persons other than authorised representatives of Soundcraft or the Dealer
have effected any replacement of parts maintenan ce ad justme nt s or repa irs to the
Equipment; and

d) the End User has used the Equipment only for such purposes as Soundc ra ft
recommends, with only such operating supplies as mee t Sou ndc raft’s spec i fica t ions
and otherwise in all respects in accordance So undc ra ft ’s rec omm e nda ti ons.

5 Defects arising as a result of the following ar e not cov ere d by thi s Wa rra nty:
faulty or negligent handling, chemical or ele c tro-c hem ic a l or electrical influences,
accidental damage, Acts of God, neglect, deficiency in electrical power,
air-conditioning or humidity control.

6. The benefit of this Warranty may not be assign ed by the End Us er.

7. End Users who are consumers should note their rights under this Warrant y are in
addition to and do not affect any other rights to which they may be en tit le d ag ai nst
the seller of the Equipment.

4 Introduction

Recommendations For

Installation

FOR UK USERS ONLY

IMPORTANT WARNING

THIS APPLIANCE MUST BE EARTHED

The wires in the mains lead are coloured in accordance with the following code:

Green and Yellow:
Blue:
Brown:

As the colours of the wires in the mains lead may not correspond with the

coloured markings identifying the terminals in your plug, proceed as follows:

The wire which is coloured Green and Yellow must be connected to the

•

terminal in the plug which is marked with the letter E or by the earth symbol.
The wire which is coloured Blue must be connected to the terminal in the plug

•

which is marked with the letter N or coloured Black.
The wire which is coloured Brown must be connected to the terminal in the

•

plug which is marked with the letter L or coloured Red.

Earth
Neutral
Live

Installation 5

Recommendations for Installation

The CPS250/CPS275 power supply is provided with front panel fixing hol e s for 19"
rack-mounting and will occupy 2U of rack space.

As with any power supply that contains a large mains-voltage transformer, it is
preferable to provide a degree of physical isolation of the unit from other electronic
equipment, particularly that which carries low level audio signals, to avoid any
possible hum pick-up. For this reason the unit is used with a long (7 metres) output
cable to enable it to be positioned away from the m ixin g con sole.

For the same reason, when rack-mounting it is preferable to avoid locating the unit
adjacent to signal processing equipment.

It should be noted that if a complete rack containing a CPS250/CPS275 unit is to be
operated from a different mains supply level, then the unit should b e withdrawn from
the rack in order to reselect the mains voltage setting, at the same time as resetting a ny
other equipment.

The other important consideration when rack-mounting the unit is the need for natural
convection of air over the case and an unrestricted air flow through the unit. Note that
air is drawn in at the rear of the unit and expelled through the fron t pa nel.

Good ventilation BELOW the unit, in the floor or back of the rack, and similarly
ABOVE the unit, at the top of the rack, will ensure a path for c ont inuou s ai r flow.

Other equipment in the rack which is known NOT to produce a signific ant amount of
heat should be mounted BELOW the unit. Equipmen t that also relies on good air flow
within the rack (ie. most power amplifiers a nd other power supplie s) should be given
due consideration and some space should be provid ed between such units and between
these and the CPS250/CPS275 unit. Forced convection, by means of a fan-tray, ma y
be desirable in this situation.

The CPS250/CPS275 will operate as a free-standing
unit without requiring any special cooling
arrangement, but should not be allowed to be
accidentally or deliberately covered over in any way.

Do not operate the unit with the top cover removed.

The air intake and outflow holes must be inspected
regularly and cleaned if necessary to maintain good
airflow through the unit. This will be particularly
important if the unit is used in a dusty environment.

Finally, some consideration should be given to the ea rthing arrangement of the system
at the centre of which are the console and the CPS250/CPS275 (and any other
Soundcraft power supply units). The console chassis is earthed, through the mains
earth, via the power supply. When rack-mounting the CPS250/CPS275(and any othe r
Soundcraft power supply units) care should be taken to avoid any possible ‘ground
loops’ in the system which would introduce audible hum to otherwise clean audio
signals. Ground loops may occur where signal proces sing equi pment, pa tche d to the
console, has its signal earth commoned to the equipment c hassis. The gro und loop is

6 Installation