Alesis D4 User manual

Alesis D4/D5 Drum Modules Service Manual i 02/19/03
ALESIS
D4/DM5 Drum Modules Service Manual
V1.00
10/17/95

Alesis D4/D5 Drum Modules Service Manual ii 02/19/03
PREFACE
This document is intended to assist the service technician in the operation, maintenance and repair of the
D4/DM5 Drum Modules. Together with the D4 and DM5 Reference Manuals, this document provides a
complete description of the functionality and serviceability of the D4 and DM5. Any comments or
suggestions you may have pertaining to the document are welcome and encouraged.
WARNINGS
TO REDUCE THE RISK OF ELECTRIC SHOCK OR FIRE, DO NOT EXPOSE THIS
PRODUCT TO WATER OR MOISTURE.
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
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.

Alesis D4/D5 Drum Modules Service Manual iii 02/19/03
SAFETY SUGGESTIONS
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.

Alesis D4/D5 Drum Modules Service Manual iv 02/19/03
Table of Contents
PREFACE ..................................................................................... ii
WARNINGS .................................................................................. ii
SAFETY SUGGESTIONS ............................................................. iii
1.00 General Descriptions............................................................. 1
2.00 Power Supply ........................................................................ 2
2.10 Battery Backup ...............................................................................2
2.20 PUP Circuit .....................................................................................3
3.00 Digital Signal Paths ............................................................... 3
3.10 The 8031 ........................................................................................3
3.11 Reset .................................................................................3
3.12 Memory mapped I/O..........................................................4
3.13 Data Entry Knob And Footswitches ..................................4
3.14 Keypad Decoding ..............................................................4
3.15 MIDI ...................................................................................4
3.20 DM3AG ASIC .................................................................................4
3.21 Address Buss Decoding ....................................................5
3.30 Mask ROMS ...................................................................................6
4.00 Analog Signal Paths .............................................................. 6
4.10 D4 Audio Output.............................................................................6
4.11 D4 Headphone Output ......................................................6
4.20 D5 Audio Output.............................................................................6
4.21 D5 Headphone Output ......................................................7
4.30 Trigger Inputs .................................................................................7
4.30 Analog-Digital Conversion..............................................................7
5.00 Test Procedures.................................................................... 7
5.10 D4 Self Test....................................................................................8
5.20 D5 Self Test....................................................................................8
5.30 Further Testing ...............................................................................9
6.00 Updates and Corrections....................................................... 10
6.10 D4 Updates.....................................................................................10
7.00 Common Solutions ................................................................ 11
8.00 Service Parts Lists ................................................................ 12
8.10 D4 Service Parts List......................................................................12
8.20 D5 Service Parts List......................................................................14
9.00 D4 Software History .............................................................. 16
9.10 Version 1.01 ...................................................................................16
9.20 Version 1.02 ...................................................................................16
9.30 Version 1.03 ...................................................................................17
9.40 Version 1.04 ...................................................................................17
10.00 D5 Software History ............................................................ 18
10.10 Version 1.01 .................................................................................18
11.00 MIDI Implementation ........................................................... 19
12.00 Service Manual History ....................................................... 28
13.00 Schematics.......................................................................... 29
13.10 D4 Schematics .............................................................................29
13.20 D5 Schematics .............................................................................31
13.30 D5 Component I.D........................................................................34
INDEX ........................................................................................... 36

Alesis D4/D5 Drum Modules Service Manual 1 02/19/03
1.00 General Descriptions
The D4 is a rather simple unit to repair, as the component count has been greatly reduced by
the use of the DM3AG ASIC (Application Specific Integrated Circuit). The basic building blocks of the
unit are the 8031 micro controller (which handles all basic unit functions such as triggers , LCD output,
Keypad input, and MIDI I/O), sample generation circuits (ASIC, DAC, Analog switch, and output
filter/buffers), and some miscellaneous support circuits such as system reset, battery backup, etc.
The DM5 (Alesis product code D5) is extremely similar in design, with the one major difference
being the use of better DACs. This has required the addition of on extra IC {D56IFT ASIC} for the
purpose of converting parallel data to a serial format and generating clock signals for use with the new
DACs. In addition this IC consolidates several other functions previously performed by discreet logic
such as memory map decoding and handling the highest order Mask ROM addressing lines. Please
note that there are several main PC Board revisions, and some differences will be noticed from unit to
unit. Reference designators refer to the D4 unless in brackets {D5 reference} or otherwise noted.
Diagram 1

Alesis D4/D5 Drum Modules Service Manual 2 02/19/03
Diagram 2
2.00 Power Supply
The power supply begins with the 9V A.C. 750 mA transformer (Alesis P3 type). After being R.F.
filtered by C26, and passing through the power switch, the A.C. is rectified into -12V, and +12V by D1
{D10}, D2 {D11}, and C2/C3 {C111/C112}, C1 {C108}. Regulators supply the +5V and -5V needed to
run the unit. Note that the +12V raw supply (From D2) {D11} is used by the system reset circuit (see
section 3.11) and battery backup (section 2.10). The D4's +12V and - 12V lines are also used to power
the output op-amps via the PUP Circuit (section 2.20). +5V and -5V lines are used to power the PUP
circuit in the D5.
2.10 Battery Backup
The battery backup circuit is more complex than it first appears, as it requires a good system
reset (see section 3.11) to function properly. The actual backup circuit consists of the 3V battery, a
current testing resistor (R38) {R92}, a steering diode (D6) {D2}, a Diode/Transistor/Resistor
combination (D7, Q3, R24) {D1, Q6, R85} that acts as a steering diode, and filter capacitor C33 {C27}.
The D/T/R combination serves a duel purpose. Besides acting as a steering diode, it also ensures that
the supply voltage level of the SRAM is higher than the level of the data buss. This prevents data
corruption during normal operation.

Alesis D4/D5 Drum Modules Service Manual 3 02/19/03
As mentioned before, the reset circuit is extremely important to battery backup. While covered
more extensively in later sections, it should be noted here that it ties into backup system at the SRAM's
chip enable line (pin 20) via Q4, and ensures that all access to the SRAM is shut off during power up,
and power down. In the case of the D5, reset is tied in through the D56IFT ASIC and Q5.
Any time any part of the backup circuit (including the SRAM) is changed, battery current should
be checked. This is accomplished by measuring the voltage across R38 {R92}. Specification for this is
1mV<VR76<8mV. Most units are in the range of 1mV to 2mV. Values outside of the normal range
usually indicate a problem, and should be troubleshot.
2.20 PUP Circuit
The PUP (quiet Power UP) circuit is designed to prevent the unit from making noise during
power up. The circuit utilizes the RESET line (section 3.11) to control the power supply lines to U42
{U2}, which is the final active stage before the outputs. The circuit essentially consists of a switchable
regulator. Q12 {Q2} and Q14 {Q4} regulate the + and - analog supplies respectively. Q10, Q11, and
Q13 {Q1, Q3} are used to switch the regulating transistors on and off depending on the state of the
RESET line.
3.00 Digital Signal Paths
3.10 The 8031
The 8031 MPU is the heart of the D4/D5's control
section. It handles everything from keypad input and MIDI
I/O, to triggers. Note that the 8031 data buss serves a
dual purpose. This buss multiplexes between low order
addresses (1st 8 bits), and data. Latch U4 {internal to
56IFT ASIC} is used to hold the low order address half,
during 8031 read and write cycles. The (U5) {U15} is
used to hold 8031 program information. The SRAM (U6)
{U16} holds system variables, as well as user parameter
data. Z1 {Z1} provides the 12MHz 8031 clock. MIDI I/O is
handled through the 8031's built in RXD (Read Serial
Data), and TXD (Transmit Serial Data) ports. Piezo input
is handled through the regular 8031 I/O ports. Keypad
decoding, DM3AG ASIC control, and LCD output are
handled through memory mapped I/O (see section 3.12).
3.11 Reset
The reset circuit is perhaps the most singly
important circuit in the D4/D5. Failures in the reset circuit
can cause symptoms ranging from loss of battery backup
to a complete machine lock up. The circuit utilizes the
positive raw supply voltage to determine when the supply
voltage is high enough for the regulators to function
properly. Diagram Error! Bookmark not defined. shows
the sequence of events during power up. When the raw
supply voltage reaches approximately 7.2V, Q1 {Q11}
switches on, pulling the base of Q2 {Q7} low and shutting it off. This allows C32 {C106} to charge via
R23 {R126}. Once C32 {C106} reaches roughly 3V, U7 {U27A} (pins 10 and 11) switches states,
Diagram 3

Alesis D4/D5 Drum Modules Service Manual 4 02/19/03
completing the reset process. The reverse process occurs anytime the raw supply falls below 7.2V.
This ensures that all functions that might cause data corruption are not functioning when the power
supply is unstable.
3.12 Memory mapped I/O
In order to easily control the vast number of hardware functions that the 8031 needs to access, a
system of memory mapped I/O is used. The basic idea is to make hardware functions appear to the
8031 as unused memory locations. That way all that the software has to do is write to a memory
location in order to send that information to a specific device such as the LCD, or ASIC. In the case of
the D5 many of the map decoding functions are incorporated into the D56IFT ASIC, reducing the parts
count relative to the D4.
74HC138 (U12) {D56IFT} performs the majority of the work in this circuit. Two things are
required before U12 becomes active. 1> A15 must be low (i.e. the 8031 is accessing the lower 32K of
address space). 2> The 8031 WRite line must be active (the 8031 is performing a memory write). A15
is used to directly control which function (memory or I/O) is active.
Once U12 is enabled, addresses A12-A14 are decoded by it, and the latch corresponding to the
value of the decoded address is strobed. At this point, data on the 8031 data buss is "written" into the
latch.
3.13 Data Entry Knob And Footswitches
The data entry knob and footswitches are read via the memory mapped latch U11 {U22}. This
allows the 8031 to directly read any changes in the status of these inputs.
3.14 Keypad Decoding
The keypad is handled through a simple polling matrix implemented through the memory
mapped latches U10 and U11 {U20, U22}. Each row is tested by the 8031, one at a time, via U10
{U20}. Any closed switches are read into U11 {U22}, and passed along to the 8031 for interpretation.
3.15 MIDI
The MIDI hardware is a standard implementation. MIDI out/thru begins at the 8031's TXD port
(pin 11) and is buffered with two inverters of U7 {U27}.
MIDI in consists mostly of the opto isolator (U8) {U23}, protection diode D4 {D6}, pullup R18
{R128}, and threshold resistor R19 {R129}.
3.20 DM3AG ASIC
The DM3AG ASIC is a complex LSI device, specifically designed for the purpose of playing
percussion samples. Obviously, the internal workings of such a device are beyond the scope of this
manual, however, a brief description of the important pins follows.

Alesis D4/D5 Drum Modules Service Manual 5 02/19/03
NAME PIN#(s) Function
MD0-MD7 27-34 8031 Data Buss Input.
CLOCK 37 Asic Clock Input (8MHz in SR-16).
DAC0-DAC16 42-51, 53-60 Output to DAC.
A0-A19 3-17, 19-23 Mask Address Buss
D0-D7 61-68 Mask Rom Data Buss
SNH0 39 Output Sample and Hold Control
SNH1 40 " " " " "
SNHIN 41 Output Sample and Hold
Inhibit.
STRES 26 Instruction reset strobe.
STB 25 Instruction latch strobe.
3.21 Address Buss Decoding
Due to the fact that we are pushing the ASIC beyond it's original design, a little extra hardware
was required to accomplish the design goals of the D4. Two limitations needed to overcome. 1> The
address space directly accessible wasn't enough for all of the samples. 2> The ASIC clock speed was
increased from earlier designs to 12MHz, making extra communication from the 8031 more difficult.
This solution to these problems takes the form of an asynchronous decoder. The purpose of the
decoder is to act as an extra set of address lines to ensure that only one Mask ROM is enabled at any
given time.
Diagram 5
Diagram 2

Alesis D4/D5 Drum Modules Service Manual 6 02/19/03
Two bits are required for each sample read (6 Mask ROMs, 0-5). This, plus the fact that there
are sixteen voices available means that 32 bits total are required for each "sample output cycle".
Latches U14-U17 provide the storage area needed to hold all 32 "extra" address bits (which are
provided by the software via memory mapped I/O [see section 3.12]). Binary counters U19-U20 are
used to synchronize the decoding process. U13 is used to decode which latch the current voice's bit
pair will come from, while U18 is used to mask the bit pair itself from the other outputs of the current
latch. U30 does the actual decoding of the bit pair, providing the single Chip Enable needed to access
the desired sample. Note that 1/2 of U43 is used as a one shot multivibrator to extend the time that the
CLear line of the binary counters (U19-U20) is held low slightly longer than SNH0 is low. This is to
ensure that the 8031 has time to communicate necessary parameters to the ASIC before the decoder
starts it's processing.
Since the D5 uses much larger Mask ROMs, this type of decoding scheme is not necessary. The
D56IFT ASIC contains all the extra hardware needed to handle extra address lines not dealt with in the
DM3AG ASIC.
3.30 Mask ROMS
The Mask ROMs contain the all of the sample information. The 18 bit address buss allows for 2
megabytes per Mask ROM. Since Mask ROMs rarely fail, most problems in this area will consist of
opens or shorts along the data and address busses. Mask Roms in the D5 have a 20 bit address buss
(thus only 2 are needed).
4.00 Analog Signal Paths
4.10 D4 Audio Output
Output from the DAC is routed to the four individual output (Main and Aux, Left and Right) by an
analog switch (U39). Output selection is controlled directly by the DM3AG ASIC. Each output section
consists of an output sample capacitor (C96-C99), and a buffer/anti aliasing filter amplifier (U42,
associated resistors and capacitors).
4.11 D4 Headphone Output
The left and right headphone outputs are a sum of the main and aux outputs sent though a pair
of X10 inverting amplifiers. The output impedance is fixed by the sum of the op-amps output
impedance, and R141/R142 in parallel with C34/C35, at roughly 150Ω. This makes the headphone outs
more compatible with 600Ωpro headphones than the 8Ωconsumer variety.
4.20 D5 Audio Output
The outputs of the '4319 DACs are buffered and low pass filtered by U2 (and surrounding
resistors and capacitors) before being routed to the outputs via A.C. coupling capacitors {C11, C3, C35,
C31}. Note that only the main outs run through the volume potentiometer just before being sent to the
outputs. Output impedances are fixed at roughly 300Ω. C1, C2, C29, and C30 provide R.F. filtering at
the outputs.