Silicon Chip – July 2019

siliconchip.com.au Australia’s electronics magazine July 2019 89

sure that the pin 1 triangle/red wire

goes to pin 1 on the connector that

you’re plugging it into, and note that

it’s possible to plug in the IDC head-

ers offset, so that some of the pins are

not connected. So avoid doing that.

The two shorter cables connect from

CON7 on the power supply board to

CON17 on the CPU board, and from

CON18 on the power supply board

to CON11 on the CPU board. On the

power supply board, pin 1 of each

connector is at bottom right. On the

CPU board, pin 1 of CON7 is near D16

while pin 1 of CON11 is near the 10μF

capacitor.

The third, longer cable connects

from CON19 on the power supply

board to CON20 on the back of the

front panel interface board. Again,

make sure that the pin 1s are wired

correctly. Pin 1 of CON20 is near to

rotary encoder RE1.

You will also need to wire up the

LCD screen. This is done using the

20-way ribbon cable. Plug one end

into CON8 on the CPU board (pin 1 is

Fig.20: a PC-based spectrum analyser plot showing the output of the DSP Active Crossover when fed with a (near) pure

sinewave. THD readings are shown at bottom; note that these were not done with a full-scale signal (which likely would

give better results) but also, they do not incorporate noise (ie, they are not THD+N readings).

A

A

B

7

7

HOLES A: 10.0mm HOLE B: 3mm

ÓSC^20 1 9 ALL DIMENSIONS IN MILLIMETRES

9

A

A

B

7

7

9

(^66) AT LEAST 60

99. 5

35 35 24. 5

5

HOLES A: 13.0mm HOLE B: 7mm HOLES C: 3mm

ÓSC 20 1 9

ALL DIMENSIONS IN MILLIMETRES

B A A

C

C C

C

9.5

24. (^515)
    72
    40
    74
    74
    13
    13
    1
    C C
    C C
    Above left (Fig.21) are the three holes required in
    the front panel controls, which are all mounted on
    the front panel PCB – the two pushbutton switches
    (S1; “Exit” and S2; “Select”) and the Rotary Encoder.
    Exact positioning on the panel is unimportant as the
    front panel PCB determines the position. At bottom
    left (Fig.22) is the cutout for the liquid crystal display,
    while below (Fig.23) are the four holes required for
    two pairs of RCA sockets (the third set would be
    identical but the separation may vary).
    ÓSC^20 1 9
    52
    74
    74
    C C
    C C
    82 7
    7
    7
    7
    4
    4 4
    4