main 0V connections used on the main board. The components, again a mixture of through hole and
surface mount devices, are soldered to the top of the board. However, because the boards used in
this project are fitted together so that their undersides face each other, the main board's components
are all accessible from the rear of the module. Although this means that you need to be a little
careful when handling the module, it does mean that fault finding is much easier than it would be if
the main board was facing the other way and no components would be visible.
The design requires plus and minus 12V supplies. The power supply should be adequately
regulated. The current consumption is 85mA and -40mA. The 45mA difference between
the positive and negative rails is almost entirely due to the constant current LED drivers. The LED
driver circuits ensure that the module takes the same current whether the LEDs are on or off. This
reduces current spikes when the LEDs are turned on and off thus reducing unwanted noise on the
power supply lines in your modular.
The two boards are fitted back to back to allow easy access to all the components.
Power is routed onto the main board via the usual 10 way keyed IDC header. Reverse polarity
protection is provided by two Schottky diodes in series with the +12V and -12V lines. Internally the
Sequencer uses three 0V connections. One is used exclusively for the digital circuitry and LEDs,
another solely for the analogue circuitry like the pot drivers, and the third one for grounding the
front panel, ground lugs of the sockets and the pot's metalwork. These three 0V connections are
made using two pins each of the middle block of six pins on the 10 way power lead. It is imperative
therefore that any power supply distribution system connects all six middle pins of the ten way
power lead to the power supply's 0V (ground). This is the expected behaviour of any Eurorack
system but should the Sequencer not behave correctly be sure to check your power lead and power
distribution system first.
Both circuit boards are the same size, that is, 249 mm (wide) x 107 mm (high). The boards are
designed to go behind a panel that is 50HP wide.
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