PA-30 will allow up to 780mA (0.78A). Remember though you can't use a PA-30 with the 3U
master panel and expect to draw 0.78A out of it without the panel getting too hot. If you are
using the 3U master panel then you should draw no more than 0.52A per rail.
If you are using a 500mA (or 0.5A) AC wallwart* then the most current you can take from
this power supply module is 125mA from each rail. That is, take no more than 125mA from
either the +15V supply or the -15V supply. Most Oakley modules take around 20 to 30mA
each from both the +15V and the -15V rails. That means you should restrict yourself to
driving a maximum of five or six synthesiser modules in your system if using 500mA wallwart.
However, you must remember that some modules may take more that 30mA. So check with
the module's User Manual or webpage to see how much current each one takes.
Various companies make linelumps** with a greater capacity than 500mA. If you can get a
1A output one than this will be able to drive up to 250mA per rail.
Some linelumps, like the Yamaha PA-20 and PA-30, use a split AC output or a centre tapped
AC output. This means it has three wires coming from it and will use a different plug from the
usual round barrel one you see on the single phase AC wallwarts. Single phase mains adapters
have only two wires coming from them so they can use a simpler connecting plug.
The Oakley PSU is recommended to be used with full wave rectification. This allows it to
utilise split AC outputs very effectively. The Yamaha PA-20 supply is rated to give an output
voltage of 35Vac (with a centre tap) at a load of 0.94A. Once rectified and smoothed this
means that a maximum current of 0.52A can be drawn from the PA-20.
Two sets of screw terminal blocks are provided for connecting the low voltage AC power
source to the board and the optional power switch. If you are using a single phase wallwart to
power the PSU module than you need only to use two terminals per terminal block.
The board has four mounting holes for stable placement onto your modular case. Care should
be taken so that the board's various board mounted components do not come into contact with
any part of your modular's enclosure. One of the holes, the bottom right hand one, is
connected to the ground pins of the two output terminals via a 'resistor', R13. In most
situations R13 is a wire link thus ensuring that the panel the PSU module is fitted to is
connected to 0V or ground of the power supply.
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 1.5A.
Three on-board LEDs, one for +15V, one for -15V and 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.
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