Alesis ANDROMEDA A6 User manual

Confidential Alesis Service Manual 8-31-0089-C
ALESIS
A6 Andromeda (A6)
Service Manual
P/N: 8-31-0089-C
The information in this document contains privileged and confidential information. It is intended
only for the use of those authorized by Alesis. If you are not the authorized, intended recipient,
you are hereby notified that any review, dissemination, distribution or duplication of this
document is strictly prohibited. If you are not authorized, please contact Alesis and destroy all
copies of this document. You may contact Alesis at [email protected].
Copyright © 2003 Alesis, LLC
ATTENTION!
THIS DOCUMENT CONTAINS SENSITIVE
PROPRIETARY INFORMATION. ALL
RECIPIENTS MUST HAVE A CURRENT NON-
DISCLOSURE AGREEMENT ON FILE WITH
ALESIS, LLC.
DO NOT DISTRIBUTE THIS DOCUMENT IN
ELECTRONIC FORM

Confidential Alesis Service Manual 8-31-0089-C
Version History
Ver A: BRS: added new cover page, added Fatar key removal instructions.
Ver B: 6/13/02 BRS: added more debugging tips, added rev C main board.
Ver C: 10/30/03 ATM: Added additional warning information for Battery replacement (per UL)

Confidential Alesis Service Manual 8-31-0089-C
Preface
This document is intended to assist the service technician in the operation, maintenance and
repair of the A6 Andromeda. Together with the A6 Reference Manual, this document provides a
complete description of the functionality and serviceability of the A6. Any comments or
suggestions you may have pertaining to the document are welcome and encouraged.
READ THIS!
In addition to any purchase price that Alesis may charge as consideration for Alesis
selling or otherwise transferring this service manual (“Manual”) to you, if you are not a
service and repair facility (“Service Center”) authorized by Alesis in writing to be an
authorized Service Center, Alesis sells or transfers the Manual to you on the following
terms and conditions:
Only Service Centers authorized by Alesis in writing are authorized to perform service
and repairs covered by an Alesis warranty (if any), and transfer of the Manual to you
does not authorize you to be an authorized Service Center. Therefore, if you perform,
or if the Manual is used to perform, any service or repairs on any Alesis product or
part thereof, any and all warranties of Alesis as to that product and any service
contract with Alesis for that product shall be voided and shall no longer apply for
such product, even if your services or repairs were done in accordance with the
Manual.
All service or repairs done by you or with reference to the Manual shall be solely your
responsibility, and Alesis shall have no liability for any such repairs or service work.
All such service or repairs are performed at the sole risk of the person performing
the service or repairs. You agree that all such work will be performed in a competent,
professional and safe manner at all times and to indemnify and fully hold Alesis and its
successors and assigns harmless in the event of any failure to so perform.
Your purchase of the Manual shall be for your own ultimate use and shall not be for
purposes of resale or other transfer.
As the owner of the copyright to the Manual, Alesis does not give you the right to copy
the Manual, and you agree not to copy the Manual without the written authorization of
Alesis. Alesis has no obligation to provide to you any correction of, or supplement to,
the Manual, or any new or superseding version thereof.
Alesis shall have the right to refuse to sell or otherwise transfer repair parts or materials
to you in its sole discretion. You shall not use, sell or otherwise transfer spare or
replacement parts supplied by Alesis to you (i) to repair or be used in products
manufactured for or by third parties or (ii) to any third parties for any purpose.
You shall not make any warranties or guarantees with respect to the products of Alesis
or the use thereof on behalf of Alesis or in your own name.
The foregoing describes the entire understanding related to sale or transfer of the Manual
to you, and no other terms shall apply unless in a writing signed by an authorized
representative of Alesis.
All Trademarks are property of their respective companies.

Confidential Alesis Service Manual 8-31-0089-C
Warnings
TO REDUCE THE RISK OF ELECTRIC SHOCK OR FIRE, DO NOT EXPOSE THIS
PRODUCT TO WATER OR MOISTURE.
The arrowhead symbol on a lightning flash inside a triangle is intended to alert the
user to the presence of un-insulated "dangerous voltage" within the enclosed
product which may be of sufficient magnitude to constitute a risk of electric shock
to persons.
The exclamation point inside a triangle is intended to alert the user to the presence
of important operating, maintenance and servicing instructions in the literature
which accompanies the product.
REPAIR BY ANY PERSON OR ENTITY OTHER THAN AN AUTHORIZED ALESIS
SERVICE CENTER WILL VOID THE ALESIS WARRANTY.
PROVISION OF THIS MANUAL DOES NOT AUTHORIZE THE RECIPIENT TO
COMPETE WITH ANY ALESIS DISTRIBUTOR OR AUTHORIZED REPAIR
SERVICE CENTER IN THE PROVISION OF REPAIR SERVICES OR TO BE OR
MAKE REPAIRS AS AN AUTHORIZED SERVICE CENTER.
ALL REPAIRS DONE BY ANY ENTITY OTHER THAN AN AUTHORIZED ALESIS
SERVICE CENTER SHALL BE SOLELY THE RESPONSIBILITY OF THAT ENTITY,
AND ALESIS SHALL HAVE NO LIABILITY TO THAT ENTITY OR TO ANY OTHER
PARTY FOR ANY REPAIRS BY THAT ENTITY.
Regarding the Power Supply Fuse
CAUTION: The product under service may employ the use of a
replaceable fuse. Danger of fire or electrocution if fuse is incorrectly
replaced. Replace with only the same type or equivalent type
recommended by the equipment manufacturer.
Regarding the Internal Battery
CAUTION: The product under service may employ the use of a internal
battery. Danger of explosion if battery is incorrectly replaced. Replace
only with the same or equivalent type recommended by the manufacturer.
Dispose of used batteries according to the manufacturer's instruction.

Confidential Alesis Service Manual 8-31-0089-C
Safety Instructions
Carefully read the applicable items of the operating instructions and these safety suggestions
before using this product. Use extra care to follow the warnings written on the product itself and
in the operating instructions. Keep the operating instructions and safety suggestions for reference
in the future.
1. Power Source. The product should only be connected to a power supply which is described either in the
operating instructions or in markings on the product.
2. Power Cord Protection. AC power supply cords should be placed such that no one is likely to step on the cords
and such that nothing will be placed on or against them.
3. Periods of Non-use. If the product is not used for any significant period of time, the product's AC power supply
cord should be unplugged from the AC outlet.
4. Foreign Objects and Liquids. Take care not to allow liquids to spill or objects to fall into any openings of the
product.
5. Water or Moisture. The product should not be used near any water or in moisture.
6. Heat. Do not place the product near heat sources such as stoves, heat registers, radiators or other heat producing
equipment.
7. Ventilation. When installing the product, make sure that the product has adequate ventilation. Improperly
ventilating the product may cause overheating, which may damage the product.
8. Mounting. The product should only be used with a rack which the manufacturer recommends. The
combination of the product and rack should be moved carefully. Quick movements, excessive force or uneven
surfaces may overturn the combination which may damage the product and rack combination.
9. Cleaning. The product should only be cleaned as the manufacturer recommends.
10. Service. The user should only attempt the limited service or upkeep specifically described in the operating
instructions for the user. For any other service required, the product should be taken to an authorized service
center as described in the operating instructions.
11. Damage to the Product. Qualified service personnel should service the unit in certain situations including
without limitation when:
a. Liquid has spilled or objects have fallen into the product,
b. The product is exposed to water or excessive moisture,
c. The AC power supply plug or cord is damaged,
d. The product shows an inappropriate change in performance or does not operate normally, or
e. The enclosure of the product has been damaged.

Confidential Alesis Service Manual 8-31-0089-C
1.0 Theory of Operation
The A6 is a 16-voice digitally-controlled real analog synthesizer.
The heart of the system is a Motorola Coldfire processor on the Main board. The code for the
Coldfire is in flash memory, and is upgradeable through MIDI. There is also a battery-backed
SRAM for holding user data.
There is a secondary processor on the Front Panel Left, an 87C52 running code from an
EPROM. This processor controls the LCD and does the LED muxing. It does not, however,
read the pot values. This is done by the Coldfire.
The analog sounds are generated from 8 Oscillator ASICs that feed 8 Filter ASICs. Each ASIC
contains two voices.
The diagram below shows the majorA6 PCBs and their functions:
Front Panel Left
Micro, EPROM,
LED muxing
pot muxing
switch matrix
LEDs
switches
pots
Front Panel Center
LEDs, switches, pots
Front Panel Right
LEDs, switches, pots
Control Control
Main
Coldfire micro
address decoding
flash memory
keyscan ASIC
digital FX
pot/tuning ADC
tuning comparator
ASIC control
MIDI
foot pedals
power regulators
LCD
Analog pot
voltages,
switch
matrix
LCD control
Analog pot
voltages,
switch
matrix
Control
Analog pot
voltages,
switch data
Analog ASIC
4 DACs for analog ASIC control signals
8 Oscillator ASICs
8 Filter ASICs
analog power regulators
Analog Master
analog output circuitry (op amps)
analog distortion
analog noise generator
Databus
Control,
FX return
Tuning
signal, FX
sen
d
Noise,
external
in
p
uts
Voice busses,
tuning,
FX busses

Confidential Alesis Service Manual 8-31-0089-C
2.0 Test Procedures
This document assumes basic familiarity with the A6 and the A6 User Manual. Please read
Appendix C of the A6 Reference Manual and familiarize yourself with it. It contains useful
information for troubleshooting.
2.10 Power Up Modes
You will need to know the A6 power up modes, since these will be helpful in debugging many
problems. The following chart is taken from the A6 User Manual:
POWER UP
WHILE HOLDING FUNCTION
Soft Button 1 Forces A6 to load default Program and Mix. This is useful if the A6 has received
corrupted data, causing it to hang.
Soft Button 2 Enters front panel debug mode.
Soft Button 3 Initializes all user RAM. This is also known as a Hard Reset. Warning, this will
erase all User Programs and Mixes, replacing them with the factory default User
Programs and Mixes!
Soft Button 4 Initializes all Global parameters, including tuning tables.
Soft Button 5 Re-calibrates Mod Wheel and Ribbon Controller.
Soft Button 6 Sends software OS out as MIDI Syx Ex dump.
Soft Button 7 Enables the A6 to receive software Syx Ex dump (OS or bootloader).
Soft Button 8 Replaces the factory default User Programs and Mixes with the User Bank
Programs and Mixes. The next time a RAM initialization is done (Soft Button 3),
these banks will be used to initialize the User Banks.

Confidential Alesis Service Manual 8-31-0089-C
2.20 Diagnostic Software Description
The A6 diagnostic software is contained within the boot section of flash memory. The software
is intended to be used to test all of the functionality of the front panel and most of the main
board. The analog boards are not tested in this mode, since those require the main software
engine to be running. Diagnostic mode is entered by holding down soft button 2 while powering
on the unit. When you are in Diagnostic mode, you will see the boot software version in the
headline.
2.21 Passive Ribbon Test
This test is done automatically when the user enters diagnostic mode. It tests the ribbon for
shorts and for proper operation of the left and right calibration points. It is “passive” because it
is done while the ribbon is not being used. In fact, if the ribbon is pressed during this test, it will
fail!
If this test fails, it most likely means the conductive layer of the ribbon (pin 2) is shorted to the
resistive layer (pins 1 and 3). It could also mean that one of the pins (1, 2 or 3) is broken or
shorted.
2.22 Pitch Wheel Center Test
This test is done automatically when the user enters diagnostic mode. It makes sure that the
pitch wheel springs are holding the pitch wheel pot sufficiently within the center of the throw.
2.23 Switch Test
This test is always going on. Simply press a switch! The name of the switch should appear on
the screen, and the “Sw :” should be in inverse characters until the switch is released. In
addition, if there is an LED near the switch, it will light up. If the switch is pressed a second
time, the LED will go off. When the microprocessor detects that a switch has been pressed and
released, the word “PASSED” appears on the screen.
When doing this test, it is only necessary to look at the LED (if there is one). If the LED
corresponding to the switch you pressed goes on (and no others), the switch is good. Looking at
the screen is only necessary for those switches with no LEDs nearby (i.e., the program keys).
Note that if you hold the SHIFT key down while pressing the soft keys, the test associated with
the soft key being pressed will not be performed. This is handy when testing the center board
keys, when you may not want to execute the test.
2.24 Pot Test
Like the Switch Test, the Pot Test is always going on. Simply turn a pot and you should see the
name of the pot on the screen, along with the pot value, which ranges from 0 to 4095. When a
pot is turned, the value should change smoothly corresponding to how much the pot is turned.
The values should stop changing immediately after (within one second) a pot is turned. If a pot
value continues to jitter after you let go, there may be a problem with the pot, the front panel, or
the ADC circuitry on the Digital Main Board.

Confidential Alesis Service Manual 8-31-0089-C
If a pot reaches the nominal min and max values, the word “PASSED” will be displayed on the
screen. The passing minimum value is 11 or less. The passing max value is 4084 or greater. It
is normal if a pot doesn’t go all the way to zero, or all the way up to 4095, due to offsets in the
ADC op amps.
Test Passing min threshold Passing max threshold
Pitch Wheel center value + 1300 center value - 1300
Mod Wheel 1000 3000
Aftertouch 400 4083
Control Foot Pedal 100 2500
Ribbon Right/Left 30 3000
Pots 12 4083
Note that a bad pot may still give a passing message (for example if it jittering), so the user must
use some common sense here. If a pot is constantly jittering, there is a problem with the pot (or
the unit).
Note that the Pitch Wheel, the Mod Wheel, the Continuous Controller Pedal, Aftertouch, and
Ribbon Controller all fall under the pot test. These controllers all have different nominal min
and max values. To speed up the test during production, a regular pedal switch may be plugged
into the CC Pedal jack and used for this test.
For the pitch and mod wheels, make sure the wheels are not electrically swapped. The pitch
wheel is on the left, the mod on the right. The pitch wheel should have a spring and should
bounce back to center.
When doing this test, turn only one pot at a time. If more than one pot is turned at a time, the
test will fail (in boot code V1.20.10 or later), because the software thinks another pot is jittering.
Also, turning more than one at a time may cause the display queue to overflow.
2.25 LED Test
To enter this test, press soft button 1. All of the LEDs on the unit should light up. The yellow
LEDs should be blinking. Hit button 1 again to turn off the LEDs. Note that any LEDs that
were on before this test will be restored and kept on.
The user should make sure that all LEDs go on, that all LEDs are centered in the window, and
all LEDs are the correct color.
2.26 MIDI Test
To perform this test, press soft button 2. A MIDI cable should be connected from MIDI OUT to
MIDI IN. This test will send a series of bytes through the MIDI port and read them back in. If it
passes, the display will read “MIDI TEST PASSED”.
2.27 LCD Test

Confidential Alesis Service Manual 8-31-0089-C
To perform this test, press soft button 3. All of the pixels on the LCD should turn black. Press
any key to exit this test.
2.28 Slow SRAM Test
To perform this test, press soft button 4 and wait a few seconds. This will test the Slow SRAM,
or battery backed RAM, on the Digital Main PCB. The first part of this test will test the RAM
for stuck bits. The second part will test the RAM address lines to make sure there are no address
pins shorted together or open. If this test passes, the display will read “SLOW SRAM TEST
PASSED”.
2.29 Test Completion
The DONE soft key (soft key 8) checks to make sure all of the tests have been performed before
letting the user exit diagnostic mode into normal keyboard mode. If any test has not been
successfully completed, the code will tell the user which test has not been done and remain in
diagnostic mode.
In addition, when all of the buttons and pots on a particular board have been successfully
exercised, the software will tell the user which boards passed (e.g., “CENTER BOARD
PASSED!”) when the DONE soft key is pressed. This is for board testing, when the user is only
interested in the status of that board, not the whole system. The software will tell the user which
switches or pots were missed on the particular board being tested.

Confidential Alesis Service Manual 8-31-0089-C
2.30 Front Panel Test Procedure
Connect the following cables/accessories to the A6 external ports:
2.311 Connect one end of a MIDI cable (4-17-0003) to the MIDI IN port and the other end to
the MIDI OUT port.
2.312 Connect Fatar Foot Switch (93) to the CC PEDAL ¼" jack of the FOOT SWITCHES/
PEDALS ports.
2.313 Connect power cord to A6 power jack.
2.314 Verify that A6 unit has current Bootloader and OS code versions with the following
steps:
a) Switch on power to A6 while holding down round SB#7.
b) Verify on A6 LCD:
ANDROMEDA SOFTWARE
BOOTLOADER V01.20.3x OS
V01.40.xx
Note: If Bootloader version is less than "1.20.31" and/or the OS version is less than
"1.40.xx", updated software should be loaded (xx - latest version).
c) Power down A6.
2.315 Enter test mode by pressing and holding down SB#2, while switching power ON, until
"*** A6 Diagnostic Mode *** " message appears on LCD display. Verify that Blue LED
is on.
2.316 Test LEDs by pressing SB#1. Verify that all LEDs on the Front Panel light up. Note that
the following LEDs should be yellow and flashing:
° "Auto Tune"
° "Audio Ext In"
° "Store"
° "Filter Bypass"
° "BP Invert"
Press SB#1 again to turn off the LEDs.
2.317 Test MIDI function by pressing SB#2. Verify that the message "MIDI TEST PASSED!"
appears on the lower center area of the LCD display.
2.318 Test LCD function by pressing SB#3. Verify that all dark pixels are visible within the
darkened area on the LCD display. Press SB#3 again to restore LCD contrast back to
normal.
2.319 Test LCD contrast pot by turning small contrast knob, found on the right side of the LCD,
back and forth while verifying that the contrast changes.

Confidential Alesis Service Manual 8-31-0089-C
2.320 Test SSRAM function by pressing SB#4. Verify that the messages, first, "TESTING
SLOW SRAM", then, "SLOW SRAM PASSED!" appears on the LCD display.
2.321 Test the Ribbon Controller by starting from the farthest end of either side of the ribbon
and sliding finger across it, while pressing down, from left to right and back, verifying
that the left and right ribbon values increase and decrease while sliding and that the
"PASSED" message appears twice on the LCD display. Note: If only one "PASSED"
message appears on the LCD display, stop test and reject unit.
2.322 Test each and every Potentiometer, one at a time, from one end of the Front Panel to the
other, verifying that both panel and LCD pot names match up and that the "PASSED"
message appears (for every pot) on the LCD display. Note: The MASTER VOLUME
pot will not show up on the LCD display when actuated.
3.323 Test the Pitch/Mod Wheel Assembly by moving the PITCH and MOD wheels while
verifying that both the panel and LCD wheel names match up. Verify that the
"PASSED" message appears on the LCD display. Also, verify that all buttons on the
Pitch/Mod Wheel Assembly actuate their corresponding LEDs and that their panel and
LCD names match up on the LCD display.
2.324 Test the Front Panel switches by pressing every button on the Front Panel, verifying that
both panel and button names on LCD match up and that their corresponding LEDs light
up when pressed (some buttons do not have corresponding LEDs). NOTE: Do not
press/test SB#1-4 -- they were tested in previous steps.
2.325 To test the Aftertouch, press down firmly and hold any of the keys in the keybed until the
"PASSED" message appears on the LCD display.
2.326 Test the Foot Switches/Pedals ports:
a) Connect the Fatar Foot Switch (93) to the CC PEDAL port (¼" jack) and actuating it
while verifying that the "CC PEDAL PASSED" message appears on the LCD
display.
b) Connect the Fatar Foot Switch (93) to the SUSTAIN port (¼" jack) and test by
actuating it while verifying that the "SUSTAIN PEDAL PASSED" message appears
on the LCD display.
c) Connect the Fatar Foot Switch (93) to the SWITCH port (¼" jack) and test by
actuating it while verifying that the "SWITCH PEDAL PASSED" message appears
on the LCD display.
2.327 Press SB#8 to identify the remaining tests to be done.
2.328 Perform remaining tests as required by A6 diagnostic software.
2.329 Follow and repeat steps 1.17 to 1.19 until all remaining tests have been performed.
2.330 If unit passes all required tests mentioned in this document, then unit has passed the Front
Panel Test!

Confidential Alesis Service Manual 8-31-0089-C
2.40 Tuning Test Procedure
2.401 Power up the A6 while holding down soft button 4. Allow the unit to tune.
2.402 Once Oscillator/Filter tuning is finished, press the AUTO TUNE button. If the message
"ALL OK" appears on the upper left hand side of the Tuning Results page, then the unit
has passed tuning. Otherwise it has failed and you should continue on.
2.403 On the Tune results page, note which voices have something other than a "T" under their
columns. These are the voices that failed.
2.404 If a voice has failed VCA calibration (check the VCA row on the LCD), here’s how to
tell which ASIC (Oscillator or Filter) has the problem:
a) Press soft button 3 (VCACAL).
b) Turn soft knob 7 (VOICE) to select the voice with the failing VCA.
c) Turn soft knob 8 (BAND) to see which VCA’s failed for that voice.
d) VCAs 10-13 are in the Osc ASIC. The rest are in the Filter ASIC.
2.405 If a voice has failed AUTO calibration (check the AUTO row in the LCD), here’s how to
tell which ASIC has the problem:
a) Press soft button 4 (OSCFRQ).
b) Turn soft knob 7 (VOICE) to select the voice that failed.
c) Turn soft knob 8 (BAND) to see which bands failed for that voice. If the failure is in
columns 1 or 2 (OSC), the the Osc ASIC is bad. If the failure is in columns 5 or 6
(FILT), then the Filter ASIC is bad.

Confidential Alesis Service Manual 8-31-0089-C
2.50 QC Procedures for Repair
These are the procedures that should be done on an A6 after it has been repaired (from the field).
Obviously, whatever was fixed should be tested thoroughly.
1. IMPLEMENT OUTSTANDING ECNs.
2. REASSEMBLE. Hot glue any connectors you may have disconnected, then re-assemble
the unit.
3. LOAD CODE. Load latest boot and OS code into the unit if necessary (as of 2/13/01 the
latest boot code is V1.20.36; the latest OS is V1.40.09). This can be done by using a
Data Disk, computer, or another A6. If required, load the boot code first to take
advantage of the faster burning capability of the latest boot code. If the unit already has
the latest code, power up while holding soft button 4 to clear global variables.
4. AUTO TUNE. After the new code is loaded (or globals are cleared), the unit should
automatically do a VCA cal and auto tune. If all voices pass tuning, you should see a
“TUNE OK” box in the upper left corner of the Auto Tune page.
5. HEADPHONE LISTENING TEST. Select a simple piano or guitar type of sound (or use
the default sound) and play a few notes and chords. Verify that the unit “sounds” in tune
through headphones.
6. KEYBOARD TEST. Play a chromatic scale starting from the lowest note to the highest
to verify that all of the keys work. Sometimes the keyboard ribbon cables can get
pinched when re-attaching the top panel to the bottom panel.
7. RIBBON TEST. Find a patch that uses the Ribbon Controller (for example, Preset 2 050
Upstairs at E’s) and verify that the Ribbon Controller works.
8. FRONT PANEL TESTS. Turn off the unit and power back on while holding soft button
2 to go into front panel debug mode. Perform all tests (knobs, leds, buttons, midi, etc.)
and verify that they all pass by pressing the “DONE” button.
9. MAIN OUTPUT TEST. Verify that the Main Outputs are working by connecting the A6
Main Outputs to an amp and speakers and playing the keyboard.
10. AUX OUTPUT TEST. Verify that the Aux Outputs are working by connecting the A6
Aux Outputs to an amp and speakers, then select AUX using the Output button (at the far
right of the unit).
11. POWER CYCLE TEST. Cycle power a few times and verify that the unit boots properly
each time.

Confidential Alesis Service Manual 8-31-0089-C
3.0 A6 Troubleshooting
The purpose of this section is to describe some of the most common problems with the A6 and
how to fix them.
Before Doing Anything
° Verify the problem before opening up the unit.
° Go into diagnostic mode by holding Soft Button 2 during power up and verify the
problem (if applicable).
° Clear memory by powering up holding Soft Button 4 during power up, allow the
instrument to re-tune, and see if the problem is fixed.

Confidential Alesis Service Manual 8-31-0089-C
3.1 General Troubleshooting
While this manual assumes that the reader has a fundamental understanding of electronics and
basic troubleshooting techniques, a review of some of techniques may help.
°Visual Inspection - A short visual inspection of the unit under test will often yield results
without the need of complex signal analysis (burnt, or loose components are a dead
giveaway).
°Self Test - Alesis products that utilize microprocessor control contain built in test
software which exercises many of the units' primary circuit functions. Self test should
always be done following any repair to ensure basic functionality.
°Environmental Testing - Applying heat and cold (heat gun/freeze spray) will often
reveal thermally intermittent components (Clock crystals, I.C.s, and capacitors are
particularly prone to this type of failure).
°Burn in Testing - Leaving a unit running overnight often reveals intermittent failures
such as capacitors that begin to leak excess current after a significant amount of time.
°Cable Checks - Wiggling cables can reveal intermittent failures such as loose cables or
poorly soldered headers. Remember to check power supply cables as well.
°Flexing the PC Board - Poor solder joints and broken traces can often be found by
pressing the PC Board in various places.
°Tapping Components - Sometimes tapping on a component (particularly crystals) will
cause it to fail.
°Power Down/up - Turning the unit off and back on rapidly several times may reveal odd
reset and/or power supply failures.
°Reset Threshold - A Variac (variable transformer) can be used to check reset threshold
levels. This can be particularly useful in helping customers with low line problems.
°Compressors - Using a compressor/limiter is often helpful when attempting to solve low
level noise problems, as well as assisting with DAC adjustments.
°Sweep Tests - Sweep generators are very useful in checking the frequency response
envelopes of anti-aliasing filters.
°Piggybacking - Piggybacking I.C.s is particularly useful when troubleshooting large
sections of logic. This is especially true when working with older units.
°Assembly/Disassembly Organization - When removing assemblies, organize screws
and clips with the assemblies that they were removed from. Organizer trays save a lot of
time during re-assembly since similar screws and clips will not be mixed with each other.

Confidential Alesis Service Manual 8-31-0089-C
3.2 Boot Problems/Unit Hanging
3.201 Unit Doesn’t Boot – No Splash Screen
° If the backlight doesn’t go on, check 5V power on the top panel.
° Check the ribbon cable going from the Front Panel Left board to the LCD.
° If the backlight goes on, but there is no splash screen, make sure the Front Panel EPROM
is properly programmed and seated in its socket (page 4 of the Front Panel Left
schematic).
° Make sure crystal for the 8052 is oscillating, and that the proper RD, WR, etc. signals are
being generated.
° Make sure the LCD contrast is turned to a good value, and make sure the LCD is working
on another unit.
3.202 Unit Doesn’t Boot – Stuck at Splash Screen
If the LCD is stuck in the splash screen, “Alesis A6 Andromeda”, it means the
microprocessor on the Front Panel Left board is working, but may have a communication
problem with the Main board, or the Main board itself may have a problem.
° Check the ribbon cable going from the Front Panel Left board to the Main board.
° Make sure the flash on the Main board (U3) is properly programmed.
° Check the pins of the microprocessor (U36), flash (U3), SRAMS (U6,U12,U17), PLD
(U29) and other fine-pin-pitch parts on the board for solder shorts or opens.
° Make sure the RESET line is in the proper state.
° Try powering up holding soft button 2 or 3.
° Verify the supply voltages on the Main Board.
° Make sure the crystals are oscillating on the Main Board. If M1 is not oscillating, then
the unit will be able to boot into diagnostic mode, but not normal mode (this is because
the normal mode software is stuck trying to initialize the DSP chip).
° Check the main board U12 IS61LV25616 SRAM. If the brand is ICSI, try replacing it
with an ISSI brand SRAM. The way to tell if this is the problem is to power up twice
quickly. If it makes it past the boot screen the second time, this might be the problem.
3.203 Unit hangs after power up or when selecting a Program or Mix
° The Mix or Program is corrupted. Power up while holding Soft Button 4 (which clears
Global Memory, but not the User bank) or Soft Button 1 (which loads a default Program
after powerup). Search for the corrupted program and write over it, or clear user memory
entirely by powering up while holding Soft Button 3.
3.204 Knobs and keyboard don’t work, unit won’t tune (stuck at “stabilizing asic
temperatures” popup)
° This is a specific problem. Check the BA02 POWER_FAIL signal. It should be high
(around 7V) during normal operation. A unit with this signal low exhibited the above
symptoms. Swapping the BA02 fixed the problem.
3.205 Unit won’t go into any powerup modes (diagnostic, load code, clear memory)
° Make sure none of the front panel buttons is stuck down.

Confidential Alesis Service Manual 8-31-0089-C
3.3 Front Panel Problems
3.301 Buttons Don’t Work or are Intermittent
° Make sure you have the latest version of the Front Panel Left PCB. If not, make sure all
of the ECNs are properly implemented. (Rev B of the board needs a 1000pF cap
soldered across pins 10 and 11 of U20).
° Make sure the diode that goes with the button is oriented correctly. If more than one
button doesn’t work, there may be a problem with whole a row or column. See if the
failing buttons correspond to a row or column.
3.302 Knobs Jitter or Don’t Reach Maximum Value or Don’t Work
° Make sure the ribbon cable going from the Main board to the Front Panel Left board is
securely seated.
° Make sure the large 60-pin ribbon cable going across the Front Panel boards is properly
seated.
° Make sure the caps and resistors at the Main Mux (upper left corner of page 2 of the
Main PCB schematic) are the correct value and are properly soldered.
° Knob jitter can be caused by voltages exceeding 5V at the ADC mux input on the Main
board. Check the inputs to U21 on the Main board. If any voltages exceed 5V, find the
source (probably the tuning or temperature bus from the ASICs). One of the ASICs
might be bad. [ECN was written to remove R62 on Main PCB – make sure it was done].
° Swap Front Panels to see if the problem is with the Front Panel or Main Board.
° Make sure the unit has the latest software (V1.40.09 or later has new anti-jitter knob
code).
° Make sure the knob caps aren’t pushed in so much that they’re touching the front panel.
Pull the plastic cap slightly so that it is not sitting against the metal.
° Try looking at the muxed analog pot signal at the input of the pot ADC (page 2 of the
Main PCB schematic), U27 pin 1. The waveform should look like a “skyline”, with each
“building” representing a pot level. If you turn all of the knobs down (to the left), the
waveform should be mostly flat, except for things like the pedal inputs, which are
normally high. If you see no signal here, it means the pot signal is not getting to the
ADC and therefore the micro.
3.303 LED Doesn’t Work
° Make sure the LED is soldered and oriented correctly.
° If several LEDs don’t work, the problem may be with a row or column in the LED
matrix. Check the row and column drivers.
3.304 Keys Don’t Work
° Make sure the two ribbon cables going from the Main board to the Fatar keybed are not
being smashed by the Ribbon Controller bracket. Make sure the cables are routed
through the opening in the bracket. If the cables were damaged, replace them.
3.305 Ribbon Controller Doesn’t Work
° Re-calibrate the ribbon by powering up while holding Soft Button 5. Make sure nothing
is touching the Ribbon Controller during this process.
° Go into diagnostic mode by holding down Soft Button 3 during power up. Verify ribbon
operation.
° Make sure the Ribbon Controller cable is plugged in properly.

Confidential Alesis Service Manual 8-31-0089-C
° Make sure the Ribbon Controller has been assembled correctly. Swap with a different
Ribbon Controller and see if the problem goes away.
3.306 LCD Backlight is Dim
° Make sure the LCD has the backlight resistors properly installed.
3.307 Pitch/Mod Wheels Don’t Work
° Re-calibrate the ribbon by powering up while holding Soft Button 5. Make sure the
pitch wheel is centered and the mod wheel is all the way down during this process.
° Go into diagnostic mode by holding down Soft Button 3 during power up. Verify wheel
operation. The wheel values should increase as the wheels are turned up.
° Make sure the wheels are wired up properly (i.e., wires are not reversed).
3.308 RAM Card Slot Doesn’t Work
° Make sure the RAM card is compatible with the A6 (must be Type I PCMCIA SRAM
card 2MB or less).
° Make sure the write protect on the card is OFF.
° Make sure the RAM card battery is good.
° Check the pins of the card connector J7 on the Main Board. Make sure none are bent or
broken.
° Make sure all of the pins of J7 are soldered correctly.
° Make sure U15 is soldered correctly.
° Test continuity of traces to and from U15.
° Replace U15.
3.4 Audio Problems
3.401 No Output from Main or Headphone Outputs
° Make sure the volume cable is securely plugged in at the Front Left Main board and the
Analog Master board.
° Make sure the Dual Master Volume Pot circuit (page 2 of the A6 Front Panel Left
schematic) has been soldered correctly. The op amp might be blown.
° Check output mute transistors (Q1 and Q2 on page 3 of the Analog Master PCB). They
may be blown and need to be replaced.
° If you are in a country that uses lower power voltages (i.e., Japan), try tweaking the AC
supply voltage to the A6 (using a device like the Elgar). If it’s sensitive, the BA02 power
supply may be bad.
3.402 Low Output from Main or Aux Outs
° Try replacing the output mute transistors Q1-Q4. If any one of these are bad, it could
cause low output on all four outputs.

Confidential Alesis Service Manual 8-31-0089-C
3.5 Tuning Problems
3.501 Single Voice Fails Tuning
° Make sure all of the components around the ASIC with the failing voice are soldered
properly and are the correct value.
° If they are, then the ASIC for that voice may be bad. Replace it and re-test.
3.502 All Voices Fail Tuning
° One of the ASICs could be shorting the tune busses. Turn off background tuning and
check the voltage on FILT_ASIC_VCA_CAL_BUS and ASIC_TUNE_BUS on the
Analog ASIC board. The voltage should be 2V. If not, remove ASICs (or disconnect
from the bus) until you’ve identified which one is shorting the line.
° Check the ribbon cables going from the Analog ASIC board to the Analog Master board
and the Main board.
3.503 Voice 2 Fails Tuning or ASIC Test – Has Problem with Pre Filter Path
This is a very specific problem on the Analog ASIC PCB. R73 and R74 are swapped in the
silkscreen, so the wrong parts are stuffed on the board. We found this problem on both the
A6 sample and the separate Analog ASIC board sent by Yahorng.
Take a look at an Analog ASIC board, near R74 and R73. The "R74" silkscreen is on the left
resistor, while the "R73" silkscreen is on the right resistor. But, actually, the left resistor is
R73 and the right is R74.
So, the left resistor should be a 20K resistor. The right one should be a 0 ohm resistor. Look
around the other ASICs to see what it should look like.