Allen&Heath WZ20 8 2 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/
INTRODUCTION
The information presented in this manual is intended for competent technical personnel to carry out service and product
support for the MixWizard WZ 20:8:2. We assume that the reader is familiar with the related electronic theory and audio
terminology, and is able to carry out basic servicing, fault-finding 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 further information on the operation and application of the MixWizard WZ 20:8:2 please refer to the USER GUIDE
publication AP2932 supplied with each console.
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 conditions the MixWizard WZ 20:8:2 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 the most
efficient service please would you quote the console serial number 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 any
covers with mains connected. Do not carry out any work within the unit while it is powered. High voltage
components are insulated for safety but should not be touched with power applied. The mains voltage
setting is indicated on the on the rear panel next to the mains socket. Check that this matches your local
mains supply. Check your mains wiring and earthing before switching on.
DO NOT REMOVE THE MAINS EARTH CONNECTION!
The chassis is always connected to mains earth. Audio 0V connects to the chassis internally. Should
problems be encountered with ground loops operate the audio ground lift switches on other equipment
connected to the unit or disconnect the cable screens at one end. Refer to the section on 'EARTHING'
in the User Guide.
INTRODUCTION, SERVICE AND TECHNICAL SUPPORT ............................................................................. 2
TECHNICAL DESCRIPTION .............................................................................................................................3
SPECIFICATION & CONNECTIONS................................................................................................................. 4
DIMENSIONS FOR FLIGHTCASING, INSTALLING THE CONSOLE.............................................................. 5
REMOVING THE CONNECTOR CIRCUIT BOARD.......................................................................................... 6-7
REMOVING A MONO or STEREO INPUT, LEFT or RIGHT CIRCUIT BOARD .............................................. 8-9
INTERNAL LINK OPTIONS ...............................................................................................................................10-11
ORDERING A CONSOLE, SPARE PARTS & ASSEMBLIES .......................................................................... 12-14
FRONT & REAR PANELS ................................................................................................................................. 15
TRANSFORMER & POWER WIRING ............................................................................................................... 16-17
MONO INPUT CIRCUIT BOARD COMPONENT IDENT .................................................................................. AG2894
MONO INPUT CIRCUIT DIAGRAM ...................................................................................................................C2894
STEREO INPUT CIRCUIT BOARD COMPONENT IDENT .............................................................................. AG2937
STEREO INPUT CIRCUIT DIAGRAM ............................................................................................................... C2937
LEFT CIRCUIT BOARD COMPONENT IDENT................................................................................................. AG2938
LEFT CIRCUIT BOARD CIRCUIT DIAGRAM sheet 1 ......................................................................................C2938
LEFT CIRCUIT BOARD CIRCUIT DIAGRAM sheet 2 ......................................................................................C2938
RIGHT CIRCUIT BOARD COMPONENT IDENT .............................................................................................. AG2939
RIGHT CIRCUIT BOARD CIRCUIT DIAGRAM sheet 1 .................................................................................... C2939
RIGHT CIRCUIT BOARD CIRCUIT DIAGRAM sheet 2 .................................................................................... C2939
CONNECTOR CIRCUIT BOARD COMPONENT IDENT .................................................................................. AG2940A
CONNECTOR CIRCUIT BOARD CIRCUIT DIAGRAM sheet 1 ........................................................................ C2940A
CONNECTOR CIRCUIT BOARD CIRCUIT DIAGRAM sheet 2 ........................................................................ C2940A
CONNECTOR CIRCUIT BOARD CIRCUIT DIAGRAM sheet 3 ........................................................................ C2940A
CONNECTOR CIRCUIT DAUGHTER BOARD COMPONENT IDENT............................................................. AG2940B
CONNECTOR CIRCUIT DAUGHTER BOARD CIRCUIT DIAGRAM ............................................................... C2940B
BLOCK DIAGRAM.............................................................................................................................................. 34
copyright © 1997 ALLEN & HEATH. All rights reserved
ALLEN & HEATH
CONTENTS
Publication .....................AP2933 Issue 1
2 2E-8SM
TECHNICAL DESCRIPTION
The ALLEN & HEATH MixWizard WZ 20:8:2 is a dedicated 8-track rack mount or desk standing mixer with 8 mono
inputs and 6 stereo inputs. All mono input channels have a 4 band 2-sweep EQ with 6 individual aux sends and Direct
output. The 6 stereo inputs have a 2 band EQ with 2 stereo cue/aux sends and 2 mono aux sends. The 8 tape return inputs
have individual level and pan controls with a stereo cue facility . In addition the MixWizard WZ 20:8:2 also has extensive
talkback facilities and an internal 1kHz sinewave oscillator for level checking The internal power supply unit is located
in the rotating connector module.
CONSTRUCTION
All metal chassis for 19" rack mount in 10U space. Comprises a 16swg steel front panel housing individual channel
circuit assemblies interconnected by means of soldered copper wire busbars. The connectors are housed in a rotating
connector module for either rack or desk mounted applications. Access to the channel internal assemblies is by removal
of the 18swg folded steel base. Access to the connectors and power supply components is by removal of the rear cover
of the connector module without the need to remove the console base. The channel assemblies may be removed for
servicing.
THE CIRCUIT COMPONENTS
The MixWizard WZ 20:8:2 is manufactured using high performance industry standard linear op-amp and discrete
semiconductor circuit devices. In particular the switches and potentiometers have proven to be durable and problem free.
When operated correctly the normal performance of the unit introduces no noticeable audio signal degradation.
AUDIO INPUTS AND OUTPUTS
All XLR connector inputs and outputs are balanced (differential) with high impedance inputs and low impedance
outputs. To use these with unbalanced equipment the -ve signal should be linked to 0V in the cable or input connector.
All unbalanced connections are line level 3-pole TRS ¼" jack sockets. All outputs are low impedance and thus capable
of driving several high impedance inputs simultaneously. All inputs and outputs are in phase.
THE PFL SYSTEM
The console PFL switches send pre-fade signals to the PFL mix bus. These signals are switched with 4053 CMOS gates
located on the RIGHT circuit board (PCB No: AG2939). The supply for the 4053 is ± 8V DC and is derived locally from
the ±16V. The gates are switched when a PFL switch is selected.
EARTHING THE AUDIO SYSTEM
The console chassis is connected to mains earth via the mains power cable. Console audio 0V is also connected to chassis.
FOR SAFETY REASONS NEVER REMOVE THE EARTH WIRE FROM THE MAINS PLUG.
Multiple earth paths cause earth (ground) loops which may result in audible hum and interference. These may be avoided
by making sure that there is only one path to earth from each piece of equipment, disconnecting audio cable screens at
one end if necessary.
INTERCONNECTIONS
Where possible use balanced connections for the CHANNEL inputs, AUX/CUE SENDs, and both L/R outputs to
minimise noise pick-up. Avoid running audio cables near to mains or lighting cables, thyristor dimmer units or power
supplies etc. These may cause audible hum and buzz. The use of low impedance sources significantly reduces
interference pick-up. Check the cables for correct wiring to avoid problems with phase reversal and unreliable
connection. The MixWizard WZ 20:8:2 follows the convention for XLR pin 2 and jack tip = signal hot (+).
ALWAYS USE BALANCED CABLES WHEN CONNECTING TO PHANTOM POWERED MICROPHONES.
WHEN USING NON-PHANTOM POWERED OR UNBALANCED MICROPHONES OR UNBALANCED LINE
SOURCES, MAKE SURE THAT THE +48V IS DISABLED TO PREVENT ACCIDENTAL DAMAGE.
INDIVIDUAL CHANNELS CAN HAVE +48V DISABLED, REFER TO THE LINK OPTIONS SECTION IN THE USER
GUIDE OR SERVICE MANUAL.
If ground loops cause problems, connect the cable screen at one end only. Balanced outputs may be connected to
unbalanced inputs and vice versa by linking the signal cold (-) to 0V ground.
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ALLEN & HEATH
SPECIFICATIONS
0 dBu = 0.775 Volts rms 0 dBV = 1 Volt rms
HEADROOM: .............................. +21dB channels
+23dB mix to output
MAX OUTPUT: XLR ................... +27dBu 2kohm max load
jack.................... +21dBu 2kohm max load
METERS:........ L, R..................... peak reading 12 bar LED
PEAK LEDs: ............................... Turn on 5dB before clipping
FREQUENCY RESPONSE:........ 20Hz to 50kHz +0/-1dB
DISTORTION: THD+Noise at +14dBu 1kHz
Channel to mix output ....................................... 0.008%
WEIGHT: unpacked 11kg, packed 14kg
CROSSTALK: Referred to driven channel at 1kHz
Channel fader off ......................... <-90dB
Channel off ........................... <-90dB
NOISE: Measured rms 22Hz to 22kHz bandwidth
Mic input EIN (150 ohm source) . <-128dB
LR output residual noise ...............<-97dBu 101dBS/N
LR faders unity mix noise............ <-82dBu 86dB S/N
POWER SUPPLY: ...................... internal, linear regulated
AC Mains input: ........................... IEC socket with lead supplied
100 to 240V AC @ 50/60Hz
factory wired to country voltage
Power consumption ..................... 35W max
Mains Fuse rating:....................... 100-120V AC T630mA 20mm
220-240V AC T315mA 20mm
CONNECTIONS
INPUTS:
Channel 1-8 IN ..............XLR ........................... pin 2 hot, 3 cold, bal PAD out .......... 2k ohm variable -60 to -20dBu
TRS jack.................... tip hot, ring cold, bal PAD in............. >10k ohm variable -30 to +10dBu
Stereo 9/10-19/20 IN TRS jack (L/M,R) ...... tip sig, ring gnd, unbal ........... >10k ohm ........-10dBV / +4dBu
Tape 1-8 IN....................TRS jack.................... tip sig, ring gnd, unbal .............. >10k ohm ........ -10dBV / +4dBu
2-Track 1 IN ...................XLR ........................... pin 2 hot, 3 cold, balanced ....... >10k ohm ........+4dBu
2-Track 2 IN ...................TRS jack.................... tip hot, ring cold, balanced ....... >10k ohm ........ -10dBV
Talkback mic IN .............TRS jack.................... tip sig, ring gnd, unbalanced .... 2k ohm ............ variable -50 to -20dBu
INSERTS:
Channel 1-8 Insert .........TRS jack .................... tip send, ring return, unbal ....................<75 ohm, >3k ohm...... 0dBu
L-R mix ..........................TRS jack.................... tip send, ring return, unbal ....................<75 ohm, >7k ohm...... -2dBu
OUTPUTS:
2-Track 1 OUT...............XLR ........................... pin 2 hot, 3 cold, balanced....................<75 ohm .......... +4 dBu
2-Track 2 OUT...............TRS jack.................... tip hot, ring cold, impedance bal ........... <75 ohm ..........-10dBV
Tape 1-8 OUT................TRS jack.................... tip hot, ring cold, impedance bal ........... <75 ohm ..........-10dBV / +4dBu
Cue 1-2 OUT ................. TRS jack.................... tip hot, ring cold, impedance bal ........... <75 ohm ..........-2dBu
Aux 1-4 OUT.................. TRS jack.................... tip hot, ring cold, impedance bal ........... <75 ohm ..........-2dBu
Monitor L,R OUT ...........TRS jack.................... tip hot, ring cold, impedance bal ........... <75 ohm ..........-2dBu
PHONES OUT...............TRS jack.................... tip left, ring right........... for stereo headphones 30 to 600 ohms
ALLEN & HEATH
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2E-8SM
DIMENSIONS
The diagrams below give the dimensions for flightcasing the console.
INSTALLING THE CONSOLE
The MixWizard Series features the ALLEN & HEATH Quick Change Connector (QCC) system. The rear connector
module may be hinged and locked into either of two positions: Rear connectors for desktop operation with the control
panel sloped at a convenient 15 degrees, or Underside connectors for 19" rack mounting in a compact 10U space. The
connector position can be easily changed at any time to fit your application.
Do not transport or carry
To change the position
remove the crosshead
locking screw on each side,
swing the connector pod into
position, and refit the two
screws.
the console with the locking
screws removed.
Do not attempt to remove
the connector pod from the
console.
19" Rack Mounting
Mount the console in the rack
using 4x M6 bolts each side for
maximum strength. We
recommend you fit the bolts with
plastic cup washers to protect the
panel, and they look good... These
should be available from the
supplier of the rack unit or a good
hardware store.
2E-8SM
Desktop Operation
The console is fitted with rubber feet to
ensure it does not slip or scratch the
work surface. The control panel is
angled at 15 degrees for operating
convenience.
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ALLEN & HEATH
REMOVING THE CONNECTOR CIRCUIT BOARD ASSEMBLY
Before beginning any service work, remove all power to the unit and disconnect any signal cables where necessary. The
rotating connector module must be set for desk top operation to gain access to the cover screws. It is not necessary to
disconnect the connector module from the main unit. Service work is best carried out with the unit inverted on a clean
work surface suitably covered to protect the mixer cosmetics. Ensure adequate lighting and use the correct tools. Access
to the connector circuit board options can be achieved without the complete removal of the circuit board.
1.) Working from the rear of the console remove screws (A) fixing the XLR connectors to the panel and using
a 12mm Nutdriver, remove jack nuts (B). Also remove the 2 screws indicated.
Remove 2 screws
B
B
A
B
B
B
A
A
2.) With the unit inverted, remove the 4 connector cover screws (C) and remove the cover.
C
Access to the connector circuit board options can be achieved at this stage by carefully easing
the circuit board assembly from the rear panel with the harnesses still connected.
It is not necessary to completely remove the circuit board assembly to change the options.
Refer to the section INTERNAL LINK OPTIONS for more details.
ALLEN & HEATH
REAR COVER
BASE
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2E-8SM
To completely remove the connector circuit board assembly
4.) First remove the base cover of the main unit to gain more access. Refer to 2 and 3 in the section
REMOVING AN INPUT, LEFT or RIGHT CIRCUIT BOARD for details on the removal of the base
cover.
5.) Cut the cable ties along the bottom edge of the connector circuit board fixing the harness to the connector
circuit board assembly and lift the circuit board assembly from the chassis.
6.) Then carefully disconnect the ribbon cable and the 4 flexible flat cables plugged into the circuit board
assembly.
7.) Before desoldering the wires connected to the circuit board, make a note of their colour and locations.
8.) The circuit board can now be completely removed from the chassis.
When all service work is complete, remove all debris such as solder, component legs and wire clippings from inside the
console and check your work carefully before reassembly. To refit the connector circuit assembly follow the above
procedure in reverse order. Make sure all harnesses are correctly aligned and plugged on. Test for correct operation.
CONNECTOR CIRCUIT
BOARD ASSEMBLY
Flexible flat cables
2E-8SM
Unit inverted with the base and connector cover removed.
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ALLEN & HEATH
REMOVING AN INPUT, LEFT or RIGHT CIRCUIT BOARD ASSEMBLY
Before beginning any service work, remove all power to the unit and disconnect any signal cables where necessary. The
rotating connector module must be set for desk top operation to gain access to the cover. Service work is best carried
out with the unit inverted on a clean work surface suitably covered to protect the mixer cosmetics. Ensure adequate
lighting and use the correct tools. Access to the channel circuit board options can be achieved without the removal of
the circuit board.
1.) If completely removing a circuit board assembly, pull off the knobs and remove the pot nuts and fader screws
from the circuit assembly to be removed. The switch caps can remain in place. If removing the LEFT circuit
board assembly remove the nut on the headphone socket.
2.) Working from the front of the mixer remove screws and nuts (A) fixing the base cover to the front panel.
A
3.) With the unit inverted, remove the 2 remaining screws (B) in the base cover and remove the base.
B
BASE
ALLEN & HEATH
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2E-8SM
Access to the input channel circuit board options can be achieved at this stage by carefully cutting
and resoldering the link options as necessary. It is not necessary to completely remove the circuit
board assembly to change the options.
Refer to the section INTERNAL LINK OPTIONS for more details.
To completely remove a circuit board assembly
4.) Identify the circuit board assembly to be removed and then cut the buss wires half way between each circuit
board. Disconnect the flexible flat cable (C) plugged into the connectors mounted along the edge of the circuit
board. If removing the LEFT or RIGHT circuit board assembly, the ribbon cable (D) and flexible flat cable
(E) will have to be carefully unplugged as well.
5.) The circuit board can now be removed.
When all service work is complete, remove all debris such as solder, component legs and wire clippings from inside the
console and check your work carefully before reassembly. To refit the circuit assembly follow the above procedure in
reverse order. Make sure all harnesses are correctly aligned and plugged on. Test for correct operation.
C
Buss wires
Cut each wire
in the centre
MONO
STEREO
LEFT
RIGHT
D
Unit inverted with the base and connector cover removed.
Overlap
and
solder
BUSS WIRES
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ALLEN & HEATH
INTERNAL LINK OPTIONS
The console is set to satisfy most applications that should be encountered. However, the following internal link options
are offered to provide alternative settings for those applications that may require them. Access to the options requires
the removal of the rear covers depending on which option settings are to be altered. Refer to the section for removing
circuit board assembly on which the link option is located. Some options involve the cutting of circuit board tracks and
soldering of circuit board links and should only be carried out by competent technical personnel. Further information
is available from ALLEN & HEATH if required.
MONO INPUT CIRCUIT BOARD
ASSEMBLIES
X8
CONNECTOR CIRCUIT
BOARD ASSEMBLY
LEFT
RIGHT
DAUGHTER CIRCUIT BOARD
ASSEMBLY
X1
Unit inverted with the base and connector cover removed.
STEREO INPUT CIRCUIT BOARD
ASSEMBLIES
X6
Channel Pre-Fade Aux Send Options
The pre-fade sends are set post-EQ and post-ON as standard. However, link options on each channel assembly allow
pre-EQ and/or pre-ON if required. Refer to the diagram below.
Channel Direct Output Source
The direct outputs are sourced post-fader as standard. A link option is available per channel to select a pre-fade
source. Refer to the diagram below.
ALLEN & HEATH
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