The power supply has two integral fuse holders in case of a problem with the power supply
circuitry itself. Two fuses are needed if you are using full wave rectification, but only one, F2,
is required for ordinary half wave rectification. The fuse type should be a slow blow or anti-
surge type. The size is 20mm. It should be rated at between one and two times the maximum
current of your wallwart. Thus a 500mA AC output mains adapter should have a fuse that is
rated between 500mA and 1A, ideally 750mA. A 1A linelump should have a fuse that is
between 1A and 2A, ideally 1.25A.
Three on-board LEDs, an orange one for +15V, a green one for -15V, and a red one for the
AC input, provide a quick visual reference that all is well. All three LEDs could be fitted
externally to the board and be mounted on a front panel. However, the recommended way is
to mount only the AC indicator on the front of the synthesiser along with the AC power
standby switch. The red LED comes on whenever AC power is applied to the unit.
As we have seen the standard circuit provides two outputs, one at +15V and one at -15V.
Both output voltages can be finely adjusted with just one trimmer. The -15V will
automatically track the output voltage on the +15V.
The output voltages are available from two screw terminal blocks. It is expected that each
terminal block will be connected to one Dizzy board. However, you can with care connect
more than one Dizzy board to each output block. Multiple Dizzy boards should never be
connected in daisy chain fashion. That is, each Dizzy board should always go back to the PSU
separately and with the shortest and thickness wire you can use.
* A wallwart is the vernacular term for a low voltage mains adapter that plugs directly into the
wall. These take the form of a black plastic block that is shaped like an oversized mains plug.
It is called a wart simply because its appearance is somewhat uglier than a normal slimline
plug.
** A linelump does the same job as a wallwart but it generally can handle greater currents.
Because of its increased size it cannot be made so that it will safely fit into a plug socket
directly. Thus the adapter sits in a black plastic box and connects to the wall via a cable and
traditional mains plug. It is therefore a black plastic lump connected to a line. The Yamaha
PA-20 and PA-30 are such linelumps.
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