Alesis ADAT BRC User manual

BRC SERVICE MANUAL
January 1, 1994
Revision 2.00

PREFACE
This document is intended to assist the service technician in the operation, maintenance and repair of
the BRC master remote control. This unit represents one of the building blocks of the complete ADAT
system. Together with the BRC Reference Manual, this document provides a complete description of the
functionality and serviceability of the BRC. 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.
i

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. Grounding the Plug. This product has a 3-wire grounding type of plug (a plug with a grounding pin) for safety purposes.
This plug can only be used in a grounding power outlet. If the plug does not insert into the outlet you are using, the outlet
probably is not a grounding type of power outlet. Contact your electrician to replace the obsolete outlet with a grounding
type of outlet instead of defeating the safety feature of the grounding type of plug.
4. 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.
5. Foreign Objects and Liquids. Take care not to allow liquids to spill or objects to fall into any openings of the product.
6. Water or Moisture. The product should not be used near any water or in moisture.
7. Heat. Do not place the product near heat sources such as stoves, heat registers, radiators or other heat producing
equipment.
8. 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.
9. 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.
10. Cleaning. The product should only be cleaned as the manufacturer recommends.
11. 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.
12. 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.
ii

DOCUMENT REVISIONS
Revision 1 4/5/93 Original Issue
Revision 1.02a 6/3/93 Added information pertaining to troubleshooting as well
as additional hardware modifications to the Main PCB.
Revision 1.04 8/6/93 Added further information pertaining to troubleshooting
as well as additional hardware modifications to the Main
PCB. Updated BRC Software History
Revision 2.0 1/1/94 Revised entire manual. Added BRC QC Test Procedure.
Added BRC System Exclusive information.
iii

TABLE OF CONTENTS
PREFACE............................................................................................................i
WARNINGS........................................................................................................i
SAFETY SUGGESTIONS.................................................................................ii
DOCUMENT REVISIONS................................................................................iii
TABLE OF CONTENTS ...................................................................................iv
LIST OF FIGURES............................................................................................vi
LIST OF TABLES..............................................................................................vi
1.0 INTRODUCTION.........................................................................................1
1.1 Scope..............................................................................................................1
1.1.1 Document Conventions ..................................................................1
1.2 BRC Reference Manual.................................................................................1
1.3 BRC Error Messages .....................................................................................1
1.4 BRC Sync Cable Requirements.....................................................................2
1.5 List Of Abbreviations....................................................................................2
2.0 BRC BUILDING BLOCKS.........................................................................3
2.1 BRC Power Supply........................................................................................3
2.2 Front Panel PCBs...........................................................................................3
2.3 Main PCB ......................................................................................................3
2.3.1 VCO Circuit....................................................................................3
2.3.2 10 MHZ Timer................................................................................4
2.3.3 ADAT Synchronization..................................................................4
2.3.4 SMPTE Interface ...........................................................................4
2.3.5 Video Interface ...............................................................................5
2.3.6 48 KHZ Interface............................................................................5
2.3.7 MIDI Interface................................................................................5
2.3.8 Main PCB Component Orientation ................................................5
3.0 BRC REPAIR................................................................................................6
3.1 BRC Assembly and Disassembly..................................................................6
3.2 Removal of the Front Panel PCBs.................................................................6
3.3 BRC Internal Cabling....................................................................................8
3.4 Front Panel Troubleshooting .........................................................................8
3.4.1 Front Panel PCB LEDs...................................................................8
3.4.2 Front Panel PCB Switches..............................................................9
3.4.3 Orientation of the Diodes and the LEDs ........................................9
3.5 Main PCB Troubleshooting...........................................................................9
3.5.1 VCO Circuit Troubleshooting ........................................................11
3.6 BRC Software Upgrades................................................................................11
3.7 Error Messages ..............................................................................................11
iv

4.0 BRC TESTING .............................................................................................15
4.1 BRC Initialization..........................................................................................15
4.2 BRC Self Test Routines.................................................................................15
4.3 QC Test Procedure.........................................................................................17
5.0 BRC SYSTEM EXCLUSIVE INFORMATION.......................................18
5.1 Alesis BRC System Exclusive.......................................................................18
5.1.1 Opcodes ..........................................................................................18
5.1.2 Global Parameter Edit Commands .................................................18
5.1.3 Song Parameter Edit Commands....................................................20
5.1.4 Action Commands..........................................................................23
5.2 MIDI Machine Control Commands...............................................................25
5.3 Universal System Exclusive MIDI Inquiry Message....................................26
5.4 Software Level (v0 v1 r0 r1) .........................................................................26
APPENDIX A
BRC SCHEMATICS...........................................................................................A-1
APPENDIX B
BRC HARDWARE UPGRADES .......................................................................B-1
BRC Main PCB Upgrades.......................................................................B-2
Power Supply Insulator Sheet..................................................................B-4
APPENDIX C
BRC SOFTWARE HISTORY.............................................................................C-1
Version 1.00.............................................................................................C-2
Version 1.01.............................................................................................C-2
Version 1.02.............................................................................................C-3
Version 1.03.............................................................................................C-4
Version 1.04.............................................................................................C-4
APPENDIX D
BRC PARTS LIST ..............................................................................................D-1
APPENDIX E
BRC QC TEST PROCEDURE............................................................................E-1
1.0 Equipment Requirements...................................................................E-2
2.0 Visual Inspection...............................................................................E-2
3.0 BRC Connections and Setup .............................................................E-3
4.0 BRC Self Tests ..................................................................................E-5
5.0 Save Setup to Tape Test ....................................................................E-9
6.0 Load Setup from Tape Test ...............................................................E-10
7.0 BRC Loop Test..................................................................................E-10
8.0 BRC Auto Punch Test .......................................................................E-11
9.0 Additional Test Requirements...........................................................E-12
10.0 Digital I/O Test................................................................................E-13
11.0 Tape Offset Test ..............................................................................E-14
12.0 Preparation For Delivery .................................................................E-14
v

LIST OF FIGURES
Figure 3-1 - BRC Assembly and Disassembly....................................................7
Figure 3-2 - Diode Orientation Within the BRC.................................................9
Figure 3-3 - LED Orientation Within the BRC...................................................9
Figure 3-4 - Pinout Diagram of EPROM Chip (U9) ...........................................12
Figure 3-5 - Pinout Diagram of Processor Chip (U10) .......................................13
Figure 3-6 - Pinout Diagram of FPGA Chip (U11).............................................14
Figure B-1 - BRC Main PCB Jumpers................................................................B-3
Figure E-1 - BRC QC Test Connection Diagram................................................E-15
LIST OF TABLES
TABLE 3.1 - BRC RIBBON CABLE INTERCONNECTION ..........................8
TABLE 3.2 - SOFTWARE COMPATIBILITY CHART...................................12
TABLE 4.1 - BRC SELF TESTS........................................................................16
vi

1.0 INTRODUCTION
1.1 Scope
This service manual is intended to serve as a primer to assist repair technicians in isolating and
correcting problems associated with the BRC Master Remote Control. This service manual includes
PCB schematics, PCB comp. IDs., top side pin diagrams for the FPGA and Processor sockets, socket
diagrams for the 2 different types of EPROMs (see section 3.6 for explanation), System Exclusive
information and a description of the hardware operation of the BRC from a servicing point of view.
1.1.1 Document Conventions
Throughout this service manual, certain conventions are followed in order to make this manual
more coherent. LEDs and signal mnemonics are spelled with all capital letters (such as RECORD LED
and SLAVECLK) while BRC functions to be performed by the operator are spelled in bold capital
letters (such as PLAY or REWIND).
1.2 BRC Reference Manual
The BRC Reference Manual (Alesis P/N 7-51-1066) is included with every BRC sold. This
manual explains the basic operation, features, and applications of the BRC. The manual contains
diagrams of both the BRC front panel controls and the rear panel interface. Moreover, the manual
contains several connection diagrams for a variety of recording situations. Please refer to this manual
when information on the operation or connectivity of the BRC is required.
1.3 BRC Error Messages
Although the BRC's LCD display will indicate various erroneous conditions which may be
encountered during normal operation (see section 3.5), the BRC's LED display does not indicate any
BRC related error messages during normal operation. However, occasionally the BRC LED display will
indicate the message "Er On xx". In these cases, "xx" is the ID number of the ADAT where the error is
occurring. When this message is displayed, it is simply informing the operator that the ADAT in
question is performing error correction of the data being read off tape. This is a normal condition of the
BRC and should not be misconstrued as a problem with the BRC itself.
In situations where the above error message is consistently displayed, it may indicate a problem
with either the tape or the ADAT playing the tape. Making a copy of the tape in question may help in
identifying the exact cause of the error message. Refer to the BRC reference manual for more details on
making digital copies of ADAT tapes.
The BRC includes a self test mode of operation which is intended to aid the service technician in
the troubleshooting of BRC related problems as well as the verification of the units various functions.
Refer to section 4.2 for details on the self test mode of operation for the BRC.
Finally, BRC software version 1.04 contains a toggle which will deactivate the error message
indication on the BRC's LED display. Refer to the latest BRC reference manual for information on this
function.
1

1.4 BRC Sync Cable Requirements
The BRC was initially shipped with a 30 Ft sync cable which connected the BRC to the master
ADAT. However, this cable sometimes caused sync problems between the BRC and the master ADAT.
It was found that due to the cable's long length, its small wire gauge, and its lack of proper grounding
and shielding, "glitches" in the sync signal were being mis-interpreted by the ADAT. To remedy this
problem, Alesis now ships every BRC with a more robust sync cable.
The type of sync cable required for proper operation over long lengths must be a 9 wire cable
which is shielded and grounded at both ends. The 9 pin D-shell male connector pins at each end of the
cable are wired to the same signal. The wire gauge of these new sync cables is 24 AWG. To determine
which type of sync cable is the correct one, look at the cable's 9 pin connectors. If the word "Alesis" is
stamped on each side of both connectors, then it is of the correct variety. Moreover, if the cable is gray
in color and contains the "Alesis" stamp on the connector, it is also of the correct variety. However, if
the cable is black in color with no markings on the connector, or if the word "Alesis" is stamped on only
one side of each connector, then this cable must be replaced with the current cable (Alesis P/N 4-71-
0002).
For cable lengths less than 6 ft. (2 meters), any off-the-shelf 9 pin cable is acceptable for
connection between ADATs in a multiple ADAT system.
1.5 List Of Abbreviations
The following is a list of abbreviations to terms used throughout this service manual.
Abbreviation Definition Abbreviation Definition
A Amps (unit of current) LED Light Emitting Diode
AC Alternating Current LRC Little Remote Control
ADAT Alesis Digital Audio Tape MHz Mega Hertz (1,000,000 Hz)
ASIC Application Specific Integrated
Circuit MIDI Musical Instrument Digital Interface
AWG American Wire Gauge MMC MIDI Machine Code
BRC Big Remote Control MTC MIDI Time Code
CD Compact Disc OSC Oscillator
DAT Digital Audio Tape PCB Printed Circuit Board
dB Decibel PLCC Plastic Leaded Chip Carrier
DC Direct Current QC Quality Control
DRAM Dynamic Random Access
Memory RAM Random Access Memory
EMI Electromagnetic Interference RMB Remote Meter Bridge
EQ Equalization ROM Read Only Memory
EPROM Erasable Programmable Read
Only Memory SMPTE Society of Motion Picture and Television Engineers
ESD Electrostatic Sensitive Device SRAM Static Random Access Memory
FPGA Field Programmable Gate Array S/W Software
GND Ground µs Microseconds (1/1,000,000 sec)
H/W Hardware V Volt (unit of voltage)
Hz Hertz (unit of Frequency) VCO Voltage Controlled Oscillator
IC Integrated Circuit W Watt (unit of power)
2

2.0 BRC BUILDING BLOCKS
Within the BRC is a power supply, the Main PCB, and four Front Panel PCBs. The Main PCB
connects to the various Front Panel PCBs via ribbon cables. Each front panel PCB has its own name and
schematic (see Appendix A). The front panel PCBs are identified as follows: Left PCB, Right PCB,
Keypad PCB and 7-Segment PCB. A description of each BRC building block is presented in the
following sections
2.1 BRC Power Supply
The power supply is a switching power supply that outputs 5 VDC to the main PCB. A copy of
the schematic is provided in Appendix A. However, there are no serviceable parts within this supply.
Alesis purchases this supply off-the-shelf from an outside vendor. If there is a problem with the power
supply, It is usually less time consuming to replace the whole power supply.
CAUTION: HIGH VOLTAGE. AVOID TOUCHING THE POWER SUPPLY WHEN THE
UNIT IS ON.
2.2 Front Panel PCBs
The four front panel PCBs are essentially a series of LEDs and switches. The controller for the
Front Panel PCBs is on the Main PCB and all of the LEDs, diodes, and switches are shown on the front
panel PCB schematics. Refer to section 3.4 for details on troubleshooting these PCBs. Refer to
Appendix A for schematic information on these PCBs.
2.3 Main PCB
The Main PCB contains all of the connectors and electronics needed to operate the BRC. At the
heart of the BRC are the three software chips: the Hitachi H8/534 microprocessor (U10), the Field
Programmable Gate Array (U11), and the EPROM (U9). Refer to Appendix A more information on the
wiring of these chips.
The Hitachi H8/534 microprocessor controls all the functions of the BRC including
communication to and from the ADATs, LED multiplexing, switch scanning, and user software
interface. It stores, receives, and generates the functions for BRC operation and uses the FPGA to
execute all required logic. Additionally, the Field Programmable Gate Array (FPGA) replaces several
logic chips with one customized logic chip. It is programmed once to control the logic within the BRC.
Finally the EPROM provides the software for the operation of the BRC.
The basis for the BRC's synchronization is its 4.8 MHz VCO which goes straight into the FPGA.
Most frequencies generated by the BRC are achieved by frequency division of the VCO by the FPGA
with the functions defined by the microprocessor.
2.3.1 VCO Circuit
The VCO, which can be founding by probing the FPGA at pin 43, is a 4.8 MHz square wave
generator from which other frequencies are produced within the BRC by division within the FPGA. A
250 Hz pulse, routed through the control logic, biases the gate of an FET that prescribes a control
voltage which sets the VCO's frequency. This creates a 4.8 MHz sinusoid at the anode of the varicap,
D12, in the tank circuit to drive the HCU04 amplifiers.
3

The 4053's in the VCO are used to lock the VCO to internal and external clock sources, thus
syncing all the other clocks. With the FPGA affecting the timing of the signal SLAVECLK (one of the
4053's controls) and with the H8/534 microprocessor affecting the signal FAST/SLOW (the other 4053's
control), the timing of the signal PCOUT, which pulses the gate of the FET, can be affected. This allows
the BRC to quickly lock its VCO to the incoming SMPTE clock.
2.3.2 10 MHZ Timer
The 10 MHZ timer (pin 3 of the H8/534 microprocessor) is used to help read the SMPTE data.
The basis for this clock is the 20 MHz crystal across pins 1 and 84 of the microprocessor. If there is a
problem in reading the SMPTE data, verify the 10 MHz's frequency. If the frequency is 10 MHZ, then
check the VCO circuit.
2.3.3 ADAT Synchronization
All ADAT syncing is done through the SYNC OUT circuit. The ADAT interfaces to the BRC
via the 9 pin Sync Out connector. Synchronization is achieved when the ADAT locks onto the 48 KHZ
signal being fed from the BRC through pin 26 of U11. The signal TCOUT provides all time code
information to the ADAT via pin 8 of J10. All communication from the ADAT, as well as information
about the ADAT's current location and mode of operation, is received through the signal line RXD2,
which runs from pins 2 and 6 of J10, through opto-isolator U12, to pin 78 on U10. Finally, all
information to the ADAT, with the exception of the time code information, is transmitted through the
signal line TXD2, which runs from pin 77 of U10, through 2 inverters (U15E and U14F), and finally out
through pin 9 of J10.
Since the ADATs also uses opto-isolators as part of its sync input circuit, the BRC sends out
three 5V DC references through connector J10, pins 3, 4, and 5. These voltages feed the opto-isolators
within the ADAT for the signals 48 KHZ, TCOUT, and TXD2, respectively.
2.3.4 SMPTE Interface
Everything related to SMPTE time code within the BRC is processed by the H8/534
microprocessor using the FPGA. There are only direct traces between the FPGA and the H8/534. If a
problem with SMPTE is suspected within the BRC, and an input SMPTE signal is being fed into pin 50
of the FPGA, and if the SMPTE circuitry appears to work, then problem is either in the FPGA, H8/534,
the traces between the two devices, and/or the VCO circuit.
There are three signals associated with the SMPTE circuit: SMPTE LEV, SMPTE OUT, and
SMPTE ON/OFF. The signal SMPTE LEV, which can be monitored from pin 5 of U10, sets the level of
the SMPTE OUT. When utilizing the +4 dBu mode, the signal SMPTE LEV is a tri-state signal, whose
output level is 2.5V peak to peak. If the -10 dBV mode is being implemented, the output of SMPTE
LEV is 633 mV peak to peak. The signal SMPTE OUT can be found on pin 9 of U11 and represents all
SMPTE output data. Finally, the signal SMPTE ON/OFF, which is found on pin 76 of U10, will turn the
SMPTE output off by going low.
For more information on setting up SMPTE within the BRC, consult the latest version of the
BRC Reference Manual.
4

2.3.5 Video Interface
Video synchronization is achieved through BNC connector J13. The signal fed into the BRC
from this connector is called VIDEO IN. This signal then feeds a circuit which is used to extract a
vertical sync signal. The output of this circuit is the signal VIDEO, which then is fed into the FPGA at
pin 29.
2.3.6 48 KHZ Interface
In order to sync the BRC to an external 48 KHZ source, BNC connector J15 is utilized. The
signal input to the BRC is called EXT CLK* and is fed into the FPGA through pin 44.
2.3.7 MIDI Interface
MIDI Input and Output circuitry is similar to that of ADAT syncing. The MIDI signal is input to the
BRC at MIDI connector J12, fed through opto-isolator U13, and in to the microprocessor via pin 81.
Likewise, MIDI out is transmitted from pin 80 of U10, through 2 inverters (U15C and U14C), to the
MIDI connector J11.
2.3.8 Main PCB Component Orientation
There is a uniform orientation of most components on the main PCB. Additionally, the
orientation for each component is outlined on the PCB itself, within the silk screen, Therefore, in
addition to having all the transistors facing the same direction, their outline is also silk screened on the
PCB.
5

3.0 BRC REPAIR
The following paragraphs represent some of the more common BRC related problems as well as
recommended solutions. To assist the service technician in the troubleshooting and repair of the BRC,
the pinout information for the EPROM, Processor and FPGA is depicted in figures 3-4, 3-5 and 3-6.
Furthermore, schematics and comp ID's for all of the PCBs within the BRC are provided in Appendix A
of this service manual.
3.1 BRC Assembly and Disassembly
The BRC is made up of a bottom case which houses the Main PCB and a front panel assembly
which houses all of the buttons, switches and front panel PCBs. When assembling or disassembling the
BRC, refer to figure 3-1 for a pictorial representation of the text that follows. Note that prior to opening
the BRC, you may first have to remove the Alesis Remote Meter Bridge (RMB) which attaches to the
BRC via 4 screws. These screws are located on the sides of the BRC and are used to fasten a sheet metal
piece from the RMB to the BRC.
If the BRC is fully assembled, you need to remove the black plastic panels which are mounted
around the perimeter of the BRC. To do this, you will need a size 10-24 hex driver. Note that the hex
screws which mount the top and bottom plastic panels to the BRC are shorter than those used to mount
the side panels. When re-assembling these pieces, pay attention to insert the correct size screw into the
correct panel. If the longer screws are used to mount the top or bottom plastic panels, there is a chance
that damage to the Main PCB will be incurred.
After the plastic panels are removed, the rack ears mounted to each side of the BRC will have to
be removed. A simple Phillips head screwdriver will do the job. Finally, remove the 12 Phillips head
screws from the front and back of the unit. These screws are located under the front panel assembly at
each end of the unit.
To open the BRC, grab the front panel in the back of the unit and slightly separate it from the
bottom case. You can then open the unit by lifting the front panel from the rear while pivoting the front
panel against the bottom case in the front as depicted in Figure 3-1. Once the unit it open, you will
notice the seven ribbon cables which connect the various front panel PCBs to the Main PCB. Whenever
possible, disconnect these cables from the Main PCB and then remove the front panel assembly away
from the unit.
3.2 Removal of the Front Panel PCBs
To gain access to the various front panel PCBs, simply unscrew the 8 Phillips head screws on the
front and back of the front panel assembly. Then turn the front panel assembly over so the buttons and
switches are facing down. Finally, remove the back plate to expose the PCBs.
All of the front panel PCBs are placed in the front panel assembly either by thread forming
screws (as is the case with the Switch PCB), snapping in, or a combination of both (as is the case with
the LCD Display PCB). If any one of the front panel PCBs that snaps in needs to be removed, perform
the steps listed below to accomplish this task.
1. Disconnect the appropriate ribbon cable from the PCB requiring removal.
2. Remove any buttons, switches, and/or light pipes that may be in the way.
3. Pull the PCB up off the positioning tabs. These are the tabs without hooks.
4. Push the lower edge of the PCB towards the top edge of the PCB and snap the PCB out.
5. Reverse the procedure to re-install the PCB.
6

Figure 3-1 - BRC Assembly and Disassembly
7

3.3 BRC Internal Cabling
All the of the PCBs connect to the Main PCB with ribbon cables. The number of wires in each
cable depends on the PCB. For all ribbon cables except the one which connect the LCD PCB to the
Main PCB, the red striped wire corresponds to pin 1 of the associated connector. Table 3.1 depicts the
interconnectivity between the various Front Panel PCBs and the Main PCB.
TABLE 3.1 - BRC RIBBON CABLE INTERCONNECTION
FROM TO CONNECTOR
CONNECTOR PCB CONNECTOR PCB TYPE
J1 Main J101 Left PCB (LEDs) 24 Pin DIL
J2 Main J102 7-Segment PCB 20 Pin DIL
J3 Main J103 Right PCB (LEDs) 14 Pin DIL
J4 Main J104 Left PCB (Switches) 16 Pin DIL
J5 Main J105 Keypad PCB 10 Pin DIL
J6 Main J106 Right PCB (Switches) 12 Pin DIL
J7 Main J107 Switch PCB 12 Pin DIL
J9 Main None LCD PCB 14 Pin DIL
Note 1: For LCD PCB, Align red stripe of ribbon cable toward the top of the Sub Panel
Note 2: On some units, the ribbon cables connecting to the main PCB at J6 and J7 were mounted in
the reverse orientation (red wire of the ribbon cable going to pin 12 instead of pin 1). For these units,
the ribbon cables must be connected to J106 and J107 in the reverse orientation as well.
3.4 Front Panel Troubleshooting
The most common problems related to the front panels are bad diodes and LEDs. If a switch
doesn't work, check its diode, the traces for that row and column, as well as the connections. When
replacing a diode and/or LED, check the orientation of the other diodes and/or LEDs in the appropriate
rows and columns to ensure proper installation.
3.4.1 Front Panel PCB LEDs
All of the LEDs used in the BRC Front Panel PCBs are arrayed in a 13 column x 16 row matrix.
When the BRC enables a specific column, it will send a signal to flip flops U3 and/or U4 to turn on the
transistor of the specific column desired. The enabling of the transistor pulls up that specific column
from ground to 5V, which is the anode of each of the LEDs in that column.
Likewise, when the BRC enables a specific row, it will send a signal to flip flops U1 and/or U2
to turn on the transistor of the specific row desired. The enabling of the transistor pulls down that
specific row from 5V to ground, which is the cathode of each of the LEDs in that row.
By enabling a specific row and column in the manner described above, a specific LED will be
selected and turned on. Note that the service technician must enable both a row and a column
simultaneously in order to light a specific LED.
The matrix has been divided on the schematics by PCB to better represent the actual layout. If
there is a problem with the matrix, the problem will either show up as multiple LEDs not lighting on one
board, or more likely, on several boards. By determining which column or row is affected on one of the
Front Panel PCBs, this column or row can be found on other front panel PCBs as well as the Main PCB.
3.4.2 Front Panel PCB Switches
8

The switches are arrayed in a 14 column x 8 row matrix. In a similar manner to the method
described for the LEDs, the processor uses U5 and U7 (both HC574 flip flops) to scan each of the
columns for a depressed switch by pulling a low on one column at a time. When a switch is pressed in a
column that is low, it creates a current on that specific row, causing that row (normally high) to pull low.
By sensing which row and column are both low, the processor determines which switch has been
depressed.
As an example, Pin 19 of U5 is low. The RECORD 1 switch is depressed which causes current
to flow through the 4.7K resistor which pulls the voltage on that row down (approximately 0.7V), which
is pin 9 of U6. Since the processor senses that pin 19 of U5 is low (the specific column) and it just
sensed that pin 9 of U6 is low (the specific row), the processor determines that the RECORD 1 switch
was depressed.
As is the case with the LEDs, the service technician must enable both a row and a column
simultaneously in order to activate a specific switch. Moreover, the switch matrix has been divided on
the schematics by PCB. By determining which column or row is effected on one front panel PCB, this
column or row can be found on other front panel PCBs as well as the main PCB.
3.4.3 Orientation of the Diodes and the LEDs
All the diodes are oriented the same on each of the front panel PCBs: Anode on the left and
cathode on the right as shown in Figure 3-2. Likewise, all the surface mount LEDs are oriented the same
on each of the front panel PCBs: Anode on top and cathode on the bottom as depicted in Figure 3-3.
ANODE CATHODE
ANODE
CATHODE
Figure 3-2 - Diode Orientation Within the
BRC Figure 3-3 - LED Orientation Within the BRC
3.5 Main PCB Troubleshooting
Aside from improperly programmed ICs, most of the problems incurred with the BRC
electronics have been related to workmanship. Prior to beginning any in depth troubleshooting of the
Main PCB, check for loose or improperly connected cables. Next, check the workmanship of the
soldered components. Finally, check the affected part of the PCB for improper contacts, excess solder or
flux, and the like. If none of these steps renders a solution to the current problem, replace ICs U10, U11
and U9, one at a time to verify that the chips have been programmed properly.
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During the course of development of the BRC, Alesis has found two types of symptoms which
indicate specific problems. These are listed below:
1. Basic functions are not working properly: In this scenario, the first things that should be
checked are the voltage of the battery and the voltage at U8, pin 32. Check both of these voltages
with power off. If the RAM chip U8 isn't supplied with enough voltage when the unit off, then
the BRC could lose some of the data stored in RAM relating to the basic operating functions.
This problem would also manifest itself as losing memory, or parts of memory, when the unit is
powered off.
2. ADATs improperly ID: This would normally manifest itself in two ways: either the ADATs ID
themselves with incorrect ID numbers, or the ADATs constantly re-ID themselves. Both of these
conditions indicate that the ADATs are having problems locking onto the 48 KHZ sync clock
signal coming from the BRC. Whenever this scenario occurs, check the four areas listed below
for potential problems.
1. VCO: This is the clock that the 48 KHZ clock is derived from. From hardware mods
described in Appendix B, C57 has been added to the Revision 1 BRC Main PCB.
Because of this modification, the 5V DC leg of this newly installed cap is in close
proximity to pin 13 of U18, which is the input to one of the output inverters for the
VCO. Excess solder or improperly cut leads could short this pin to 5V, effectively
killing the VCO and the 48 KHZ line as well. Likewise, if C57 is improperly
soldered, it could come loose and make temporary contact with pin 13 of U18, which
will result in distortion of the VCO. Finally, if C57 is bent over U18, it could also
cause distortion of the output of the VCO. If any of the items mentioned above appear
on the Main PCB in question, re-solder C57 in accordance with Appendix B, clean
away any excess solder, visually inspect the C57 lead proximity to U18, and orient
C57 away from U18. This modification has been incorporated onto the new Revision
2 BRC Main PCB layout.
2. 48 KHZ output to ADAT: This problem deals with the 48 KHz output at pin 7 of
connector J10. R84 is 48 KHz and R83 is its 5V reference to the ADAT's opto-
isolator circuit (see section 2.3.3). With an ADAT connected, check for a slight
voltage drop across R83, and check R84 for the proper signal. Verify that both
resistors are properly inserted and soldered on the board. Also, verify that there isn't
continuity between the resistors.
3. DB9 output connector J10: Check for improper connections, pins not soldered,
damage to the connector, and the like.
4. Cable between BRC and first ADAT: If this isn't an Alesis approved cable (see
section 1.4), problems could result. Alesis Product Support should have verified with
the customer the type of cable being used prior to issuing the Repair Authorization
(RA), and therefore it is unlikely that the cable is the problem. However, if this is in
question, contact Alesis Product Support.
Finally, there is the problem of BRCs intermittently resetting. The symptoms of this problem are
similar to those relating to BRCs improperly IDing. However, in this case, the BRC will continue to
cycle power every so often. That is, the BRC LCD back light will dim momentarily. If the LCD display
does not dim, then the problem is probably related to one of the above items.
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For BRCs that intermittently reset, there is no concrete solution other than replacing the power
supply. However, this solution does not always work. If you have a unit which is exhibiting this
symptom and it cannot be resolved with a new power supply, contact Alesis Product Support so that this
unit can be replaced.
3.5.1 VCO Circuit Troubleshooting
If this circuit doesn't work properly, the VCO might be slightly off. This will result in syncing
problems, especially when trying to sync to SMPTE. Since the VCO is the basis for all the clocks in the
BRC, which, in turn, is the basis for all the syncing, this is the first place to look for a problem. Note: If
there are problems with syncing to SMPTE and the VCO is suspected, check the components and solder
connections to make sure that they are all in good working order.
3.6 BRC Software Upgrades
Note that when the BRC software is to be upgraded, it is necessary to verify the microprocessor,
FPGA and EPROM compatibility prior to the upgrade. Refer to Table 3.2 for the compatibility chart of
the various software versions of these devices. To determine which version of software in currently
installed in the BRC, press the MIDI\UTIL button repeatedly until the LCD displays the software
version.
Furthermore, the microprocessor and EPROM chips can be re-programmed for re-use in the
BRC. Therefore, when old versions of these devices are removed from the BRC, they should be returned
to Alesis for updating. However, the FPGA chip is programmed only once and cannot be re-
programmed. If the FPGA requires upgrading, the older version is no longer useful and can be thrown
away.
Finally, note that earlier versions of BRC software utilized a 28 pin 27C512 EPROM.
Installation of this chip in the 32 pin socket for U9 was accomplished by seating the EPROM in the
lower 28 pins of the socket. With the current software, however, the required EPROM is a 1 Meg, 32 pin
27C010 device.
3.7 Error Messages
Error messages from the LCD display are typically a result of memory problems. In these cases,
the SRAM chip U8 is not holding some of the basic operating instructions that were stored during the
last reset. If this problem occurs:
1. Check the battery.
2. Check U8, pin 32 with unit off. Voltage should be equal to or greater than 2.5V DC.
3. Check D2
If the voltage at pin 32 of U8 is less than the value listed in step 2, the battery will need to be
replaced. However, if the battery is replaced and the voltage at U8 pin 32 is still less than 2.5V DC,
check diode D2. A bad diode D2 will drain the battery prematurely.
Note that if the LED displays the message "Er on xx" where xx is the ID number of the ADAT
where the error is occurring, refer to section 1.3 for more information on this type of error message.
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TABLE 3.2 - SOFTWARE COMPATIBILITY CHART
Software Revision EPROM (U9) FPGA (U10) Processor (U11)
1.00 27C512 Rev 0 (1.00) 1.00
1.01 27C512 Rev 1 (1.01) 1.00
1.02 27C512 Rev 2 (1.02) 1.01
1.03 27C010 Rev 2 (1.02) 1.01
1.04 27C010 Rev 3 1.02
FPGA Version 1.02 adds a one-shot to the video input circuit to filter out possible
multiple transitions from the video sync separator when the video input signal is less
than perfect. This version of the FPGA can be replaced in any BRC independent of
other hardware or software changes for improvement in video synchronization.
Figure 3-4 - Pinout Diagram of EPROM Chip (U9)
Figure 3-5 - Pinout Diagram of Processor Chip (U10)
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Figure 3-6 - Pinout Diagram of FPGA Chip (U11)
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