Allen&Heath WZ 20S SERVICE MANUAL

ALLEN&H

EATH

WARNING – HIGH VOLTAGES

Power Supply Unit (PSU) work should only

e carried out by qualified personnel.

b

We recommend that you use an approved Allen & Heath

service centre for all power supply work.

Please contact your local Allen & Heath distributor for more details.

http://www.allen-heath.com/

MixWizard Series

WZ20S

Stereo Audio Mixing Console

SERVICE MANUAL

Publication No: AP3638

CONTENTS

INTRODUCTION, SERVICE AND TECHNICAL SUPPORT.................3

FLIGHTCASING THE CONSOLE & DIMENSIONS .............................4

SPECIFICATIONS & CONNECTIONS.................................................5

ORDERING A MIXWIZARD WZ20S UNIT, OPTIONS & MANUALS ....6

ORDERING SPARE ASSEMBLIES......................................................6

ORDERING SPARE PARTS.................................................................7-8

MONO INPUT BOARD COMPONENT IDENT.....................................AG3379

MONO INPUT BOARD CIRCUIT DIAGRAM........................................C3379

STEREO INPUT BOARD COMPONENT IDENT .................................AG3408

STEREO INPUT BOARD CIRCUIT DIAGRAM....................................C3408

LEFT BOARD COMPONENT IDENT...................................................AG3627

LEFT BOARD CIRCUIT DIAGRAM (PAGE 1 OF 2)................................C3627

LEFT BOARD CIRCUIT DIAGRAM (PAGE 2 OF 2) ................................C3627

RIGHT BOARD COMPONENT IDENT.................................................AG3626

RIGHT BOARD CONNECTOR CIRCUIT DIAGRAM (PAGE 1 OF 2)......C3626

RIGHT BOARD CONNECTOR CIRCUIT DIAGRAM (PAGE 2 OF 2)......C3626

CONNECTOR BOARD COMPONENT IDENT.....................................AG3632

CONNECTOR BOARD CIRCUIT DIAGRAM (PAGE 1 OF 3)..................C3632

CONNECTOR BOARD CIRCUIT DIAGRAM (PAGE 2 OF 3)..................C3632

CONNECTOR BOARD CIRCUIT DIAGRAM (PAGE 3 OF 3)..................C3632

Warning to the Service Engineer

Allen & Heath warns that any unauthorised changes or modifications to the WZ20S unit may
invalidate the legal compliance of the unit and could void the user’s authority to operate the
equipment.

WZ20S Service Manual AP3638 Issue 2. Copyright © 2005 Allen & Heath. All rights reserved

MANUFACTURED IN ENGLAND BY: ALLEN & HEATH AGENT:

ALLEN&HEATH

Kernick Industrial Estate
Penryn, Cornwall, TR10 9LU. UK

http://www.allen-heath.com

2 WZ20S SERVICE MANUAL

Introduction

The information presented in this manual is intended for competent technical personnel to carry out
service and product support for the MixWizard WZ20S console. We assume that the reader is
familiar with the related electronic theory and audio terminology, and is able to carry out basic
servicing, faultfinding and repair of audio equipment of this type. Service personnel should also be
familiar with audio systems, mains earthing and power requirements, as well as handling precautions.

For information on the configuration, operation and application of the MixWizard WZ20S
please refer to the User Guide.

Whilst we believe the information in this manual to be reliable we do not assume responsibility for
inaccuracies. We also reserve the right to make changes in the interest of further product
development.

Service and Technical Support

Under normal operating conditions the MixWizard WZ20S does not require user maintenance or
internal calibration. Any service work required should be carried out by qualified technical personnel
only.

We are able to offer further product support through our worldwide distribution network. To help us
provide an efficient service please quote the console serial number, the date and place of purchase in
any communication regarding this product.

SAFETY WARNING!

Mains electricity is dangerous and can kill. Mains voltage is
present within the unit.
Do not remove the cover with mains electricity connected. To
ensure your safety, mains earth is connected to the chassis
through the power lead. Do not remove this mains earth
connection.
To avoid the risk of fire, replace the mains fuse with the correct
value and type as indicated on the rear panel.

Before switching on your console, check that the fuse is of the correct rating and
type. This is clearly marked on the rear panel. Do not replace the fuse with any
other type, as this could become a safety hazard and will void the warranty.

General Precautions

Your WZ20S is ruggedly constructed to give many years of reliable operation. However, you will
extend the life of the console and preserve its cosmetics by applying these simple common sense
precautions.

• Avoid storing or using the mixing console in conditions of excessive head or cold, or in positions

where it is likely to be subject to vibration, dust dirt or moisture.

• Do not use any liquids to clean the control surface of the console, a soft dry brush or dry lint-free

cloth is ideal.

• Use only water or ethyl alcohol to clean the trim and scribble strips. Other solvents may cause

damage to paint or plastic parts.

• The faders, switches and potentiometers are lubricated for life. The use of electrical lubricants on

these parts is not recommended.

• Avoid using the console close to strong sources of electromagnetism radiation (e.g. video

monitors, high power electric cabling): this may cause degradation of the audio quality due to
induced voltages in connecting leads and chassis.

WZ20S SERVICE MANUAL 3

Flightcasing the Console

If the console is to be regularly moved we recommend that it is installed in a foam-lined flightcase. At
all times avoid applying excessive force to any knobs, switches or connectors.

Dimensions for flightcasing the console are shown below:

Dimensions

Width Height Depth

Desktop ........................ 483mm (19”)................. 192mm (7.6”).................530mm (20.9”)

Rack mounted .............. 483mm (19”) ................. 444mm (17.5”) 10U .......135mm (5.3”)

Packed.......................... 590mm (23.2”).............. 260mm (10.2”)...............610mm (24”)

Unpacked Packed

Weight........................... 10kg (22lbs).................. 13kg (29lbs)

4 WZ20S SERVICE MANUAL

Specifications

0dBu = 0.775 Volts rms +4dBu = 1.23V rms

0dBV = 1 Volt rms -10dBV = 316mV rms

INTERNAL HEADROOM:

....................................... Channels ........................+21dB

....................................... Mix to output................... +23dB

MAXIMUM OUTPUT LEVEL:

XLR ..........................................+26dBu into >2k ohm load

TRS jack ...................................+21dBu into >2k ohm load

PEAK INDICATORS:..............Turn on 5dB before clipping

METERS:

........... MIX 1,2 / MONITOR Peak reading 12 led 3 colour

FREQUENCY RESPONSE:

......................................................20Hz to 50kHz +0/-1dB

DISTORTION: THD+noise @ +14dBu 1kHz

............................................................................ < 0.006%

CROSSTALK: Channel shutoff measured at 1kHz

................................................................................ < 90dB

NOISE: Measured rms 22Hz to 22kHz

MIC EIN: referred to 150 ohm source

................................................................................-128dB

RESIDUAL OUTPUT NOISE:

........................................... XLR -90dBu (-94dB S/N)

........................................... TRS jack -94dBu (-94dB S/N)

MIX NOISE, CH ROUTED:

........................................... XLR -86dBu (-90dB S/N)

........................................... TRS jack -90dBu (-90dB S/N)

POWER SUPPLY: 100 to 240V AC @ 50/60Hz

Internal switch mode power unit with auto sensing mains
input.

Power Consumption............................................35W max

Mains fuse rating 100-240VAC .................T500mA 20mm

Connections

INPUTS:

Mic in...................... XLR.....................pin 2 hot, 3 cold, balanced ..............................2k Ohm......... variable –60 to -20dBu

Line in..................... TRS jack.............tip hot, ring cold, balanced ..............................>10k Ohm..... variable –30 to +10dBu

Stereo Ch in A........ RCA PHONO ......unbalanced......................................................>10k Ohm..... variable –20 to +10dBu

Stereo Ch in B........ TRS jack ............. tip hot, ring cold balanced ...............................>10k Ohm..... variable –20 to +10dBu

EXT in 1-2 .............. TRS jack.............tip hot, ring cold balanced ...............................>10k Ohm..... variable –10dBV (+4dBu option)

OUTPUTS:

Direct out 1-4.......... TRS jack.............tip hot, ring cold, impedance balanced..........<75 Ohm ........ 0dBu

Mix out 1-2 ............. XLR.....................pin 2 hot, 3 cold, balanced ............................<75 Ohm ........+4dBu

Mix out 2................. TRS jack.............tip hot, ring cold, impedance balanced..........<75 Ohm ........ -2dBu

Mono out ................ XLR.....................pin 2 hot, 3 cold, balanced ............................<75 Ohm ........ +4dBu

Aux out 1-6............. TRS jack .............tip hot, ring cold, impedance balanced..........<75 Ohm ........ -2dBu

Phones out 1, 2...... TRS jack .............tip left, ring right.............................................for stereo headphones 75 to 600 Ohms

INSERTS:

Mono Channel:

Send....................... TRS jack ............. tip send, ring return, unbalanced................... <75 Ohm ........ 0dBu

Return .................... TRS jack ............. tip send, ring return, unbalanced...................>3k Ohm

Mix out 1-2:

Send....................... TRS jack ............. tip send, ring return, unbalanced...................<75 Ohm ........ -2dBu

Return .................... TRS jack ............. tip send, ring return, unbalanced...................>7k Ohm

WZ20S SERVICE MANUAL 5

ORDERING A CONSOLE

To order a new MixWizard console please specify the model number and AC mains voltage.

MODEL DESCRIPTION ORDER CODE

MIXWIZARD WZ20S 4 Mono + 8 Stereo Input Channels WZ20S/volts

ORDERING AN OPTION

To order an option please specify the model number required.

RIAA OPTION WZ20S RIAA DUAL INPUT OPTION W21442/20S-RIAA

FADER START WZ20S MONO FADER START OPTION 002-496

FADER START WZ20S 4M8S FADER START OPTION 002-501

MANUALS AND SUPPORT DOCUMENTATION

DESCRIPTION ORDER CODE

MIXWIZARD WZ20S User Guide AP3634

MIXWIZARD WZ20S Service Manual AP3638
MIXWIZARD WZ20S Flyer AP3637

SERVICE TOOLS

The tools required to service the MixWizard WZ20S are standard to an electronics service workshop
and are easily obtainable. The following items are necessary for disassembly and service access:

1-point Crosshead screwdriver (M3, M4, 4AB) AT0004

11mm AF Nutdriver (potentiometer, headphone socket and jack nuts)

ORDERING AN ASSEMBLY

The following assemblies for the MixWizard WZ20S are supplied fully tested. Please quote the
description and order code for the part required.

Printed circuit board (PCB) assemblies:

Mono Input PCB assembly 002-483
Left PCB assembly 002-484
Right PCB assembly 002-485
Stereo PCB assembly 002-487
Connector PCB assembly including Power Supply 002-486

IDC connector harnesses:

WZ20S 16 way Main harness AL3669
WZ12/16/20S/464 34 way Master harness AL3518

6 WZ20S SERVICE MANUAL

ORDERING A SPARES KIT

It is recommended that the spares kit order code 002-491 is held and maintained by the service agent
to enable in-field service repairs to the WZ20S independent of the ALLEN & HEATH factory.
Commonly available items such as resistors, capacitors, tools and soldering equipment are not
included. The contents of the kit are listed below and are supplied in a cabinet of drawers. Individual
spare parts may be ordered. Please quote the description and order code for the part required.

DESCRIPTION ORDER CODE QTY

Fixings:

Screw M3 x 6mm TT Pan Pozi Black AB0071 10
Screw M3 x 8mm Pan Pozi Black AB0073 10
Screw M3 x 10mm Pan Pozi Black AB0076 10
Nylock Nut M3 AB0102 10
Screw M3 x 4mm Pan Pozi Black AB0233 10
Washer M3 Shakeproof AB0244 5
Screw 4AB x ¼ Pan Pozi Plated AB0252 1
Screw 4 x 5/16” Poly Pan Pozi Black AB2810 10
Screw M3 x 6mm TT CSK Pozi Black AB2929 5
Fastfoot AK0102 2

Knobs and caps:

Knob Red & Grey 11mm D AJ2074 10
Knob Blue & Grey 11mm D AJ2075 10
Knob Light Blue & Grey 11mm D AJ2076 10
Knob Green & Grey 11mm D AJ2077 5
Knob Dark Grey & Grey 11mm D AJ2078 10
Knob Yellow & Grey 11mm D AJ2079 10
Knob Brown & Grey 11m D AJ2080 5
Button 5.5mm Square Grey AJ2864 10
Button 10x5mm Rectangular Grey AJ2865 5
Button Round Black AJ2887 3
Button 5.5mm Square White AJ2960 10
Button 5.5mm Square Red AJ2961 10
Button 10 x 5mm Rectangular White AJ2962 10
Switch Cap Tall AJ8071 5
Fader Knob 11mm White+Black Line AJ8078 5
Fader Knob 11mm Yellow+Black Line AJ8080 5
Fader Knob 11mm Blue+Black Line AJ8081 10

Faders, Potentiometers, Switches and connectors:

Pot 20KK (203K 11mm wide) AI8003 10
Pot 20KB centre click (203B 11mm wide) AI8004 10
Pot 200KC x 2 (204C 1mm wide) AI8005 10
Pot 20KB x 2 centre click (14mm wide) AI8006 5
Pot 20KK x 2 (203K 14mm wide) AI8007 10
Pot 10KAC x2 (103AC 14mm wide) AI8008 10
Pot 5K (502RD 11mm wide) AI8111 5
Fader 10KD 100mm AI8117 5
Fader 10KD x 2 100mm AI8118 10
Switch 2PCO Latching 90° AL0162 5
Jack Socket Headphone AL0328 1
XLR 3 Pin Female Vertical PCB Mount AL2410 3
XLR 3 Pin Male Vertical PCB Mount AL2411 3
Phono Socket 24mm Dual Vertical PCB Mount AL3240 5
Jack Socket ¼” Stereo Unswitched AL3407 5
Jack Socket ¼” Stereo Switched AL3410 5
Switch 2PCO Latching Vertical AL8057 3
Switch 2PCO Latching 90Deg AL8065 5
Pot Nut 9mm AB8050 20

WZ20S SERVICE MANUAL 7

LEDs and Semiconductors:

Transistor BC549 NPN AE0020 10
Transistor BC638 PNP TO92H AE0037 5
IC TL072 Dual Op-Amp AE0046 5
Transistor BC637 NPN TO92H AE0068 5
IC LM339N Quad Comparator AE0071 3
Transistor J111N FET T092B AE0083 2
LED 3mm T1 Red AE0086 5
IC CMOS 4053B AE0117 5
IC Op-Amp NE5532N AE0221 5
Transistor 2N4403 PNP AE0273 10
IC SSM2142P Bal Out Driver AE0302 3
LED Bar Rectangular 12 Way AE2701 2
Transistor BC556B PNP AE3001 5
LED Rect Green 5X2MM Flat Top AE3501 5
LED Rect Red 5X2MM Flat Top AE3502 2
IC TL072 Op-Amp SIL AE8070 5
Transistor MPSA92 PNP AE8119 1

POWER SUPPLY:

Insulation Guard AA3509 1
Mains Lead IEC-2 Pin (Europe) AH0205 ­Mains Lead IEC-3 Pin (UK) AH0206 ­Mains Lead IEC-3 Pin C33 (USA) AH0323 ­Fuseholder 20mm PCB Mount AL3178 ­IC Opto-Isolator 4N35 AE0266 1
Diode Zener 47V 500mW AE2999 1
Transistor TIP122 AE3215 1
Diode BYV27-400 2A AE3469 5
Diode BYV26E 1A 1000V AE3470 5
Diode P6KE200A AE3471 3
Transistor Mosfet STP4NA80FI AE3472 3
IC SMPS UC3842AN AE3473 3
IC TL431 Voltage Reference AE3475 1
Bridge Rectifier 2KBP04M AE3477 2
Inductor 4.7uH 600mA AM3467 2
Transformer Wizard Switch Mode AM3476 1

Miscellaneous:

MixWizard Box + Fittings AP2915 -
Flex cable 39 way 200mm AH2900 2
Flex Socket 12 Way 90Deg AL2226 ­Flex Socket 12 Way Straight AL2227 ­Flex Socket 8 Way 90Deg AL2901 ­Flex Socket 39 Way Straight AL2902 -

8 WZ20S SERVICE MANUAL