ALLEN & HEATH Qu-16 Specification sheet

ALLEN&HEATH TB1403 - Qu-16 Phantom Power Hot Plugging Page 1/6
ALLEN&HEATH
TECHNICAL NOTE
Copyright © 2014 Allen & Heath Limited. All rights reserved
Allen & Heath Limited, Kernick Industrial Estate, Penryn, Cornwall, TR10 9LU, UK
www.allen-heath.com
Work to be carried out by a competent, qualified engineer.
Allen & Heath cannot be held responsible for the actions of third party engineers.
Risk of electric shock.
Switch mode PSUs may present up to 400VDC.
The factory supported warranty may be invalidated if work is carried out by non-authorized persons.
SUBJECT: Qu-16 +48V Phantom Power Hot Plugging
DATE: June 2014
MODEL(S): Qu-16
We have received feedback from a small number of users who have reported that,
when ‘hot plugging’ microphones on channels with +48V phantom power enabled,
noise can be heard on adjacent channels.
We do not recommend hot plugging condenser microphones when phantom power is
enabled as it could cause damage to your equipment.
However, we understand that occasionally a customer may accidentally hot plug a
microphone when +48V is enabled so we updated the design of the Audio Board
(AG8891) to reduce noise when hot plugging occurs. This update was published as
RECN2963.
We have recently updated the Audio Board to ISS_3 which is explained in RECN2996.
The ISS_3 Audio Board (AG8891_3) is installed in mixers with a serial number of
QU16X-444230 or later. ISS_3 boards do not produce noise when hot plugged.
If a customer complains about hot plugging noise, and has an ISS_2 Audio Board
(AG8891_2), then you can perform a modification to significantly reduce the noise.
If the mixer has a serial number earlier than QU16-003300
Please follow Step 1 (page 3) and Step 2 (pages 4-6) of the document.
If the mixer has a serial number between QU16-003300 and QU16X-444229
Please follow Step 2 (pages 4-6) only.
Please note that this is not a compulsory update and should be performed at your discretion
For further information contact Allen & Heath Technical Support at
www.allen-heath.com/support
®

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Disassembly Instructions
For disassembly instructions please see pages 6,8,10 & 18 the Qu16 service manual which can be
downloaded from our website.
Required Components
We can provide these free of charge on request.
Contact Technical Support to order.
Description Quantity A&H Part Number
Electrolytic Capacitor 1000uF 6.3V 1 AF8123
Mylar Capacitor 0.0022uF 100V 2 AF0151
17mm H12 Rubber Sleeving 1.2mm 1 AH0316
Soldering Iron & Solder
SMD Tweezers
T8 Torx Screwdriver
T10 Torx Screwdriver
9mm Nut Driver
Required Tools
T8
T10
9mm

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MODIFICATION INSTRUCTIONS FOR AG8891 ISS_2 ONLY
STEP 1 - DIODE REMOVAL
FOR SERIAL NUMBERS BEFORE QU16-003300
Remove the base of the Qu-16. Look at the rear of the Audio Board (AG8891)
On the Audio Board (AG8891), check for red glass LL4148 Diode at D1, D2, D3, & D4.
Are the diodes on the board?
There are 68 diodes;
34 on the front, 34 on the back.
REMOVE ALL 68 DIODES
GO TO STEP 2 (PAGE 3)
YES NO
GO TO STEP 2 (PAGE 3)

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Solder Electrolytic 1000uF 6.3V capacitor to +5VA / GND
Place rubber sleeving on capacitor legs
Solder the positive (+) leg to +5VA
Solder the negative (—) leg of to GND
Bend the capacitor around the edge of the
PCB

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Solder Mylar 0.022uF 100V capacitor to MIC 4
Solder one pin to the cathode pads of D2/D3
Solder one pin to GND net of C174
Bend Capacitor Flat

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Solder Mylar 0.022uF 100V capacitor to MIC 7
Solder one pin to the cathode pads of D2/D3
Solder one pin to GND net of C174
Bend Capacitor Flat