Brc Internal Cabling; Front Panel Troubleshooting; Front Panel Pcb Leds; Table 3.1 - Brc Ribbon Cable Interconnection - Alesis ADAT BRC Service Manual

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
CONNECTOR
J1
J2
J3
J4
J5
J6
J7
J9
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
PCB CONNECTOR
Main J101
Main J102
Main J103
Main J104
Main J105
Main J106
Main J107
Main None
TO
PCB
Left PCB (LEDs)
7-Segment PCB
Right PCB (LEDs)
Left PCB (Switches)
Keypad PCB
Right PCB (Switches)
Switch PCB
LCD PCB
8
CONNECTOR
TYPE
24 Pin DIL
20 Pin DIL
14 Pin DIL
16 Pin DIL
10 Pin DIL
12 Pin DIL
12 Pin DIL
14 Pin DIL