[sdiy] 'advance power' psu setup (basic questions)

[Julian]

Hello there,

I have acquired an 'advance power' linear psu, (farnell part number :
183-829 )

Its a higher ampage psu then i was relay after, at 3.4 amp, but that's the
way it turned out.  To fuse the output, should i fuse both the positive and
negative rails, or just the ground?

Which leads on to my next question: the pcb of the psu has 4 terminals, +12v
out, -12v out, + and - sense.  I shall short the sense terminals to their
respective outputs, as voltage drop wont be an issue, but where should i run
the combined AGND and DGND to? (these are coming off my modulars power
distribution busses...)

The wire the grounds the L frame chassis to the transformer has an
additional spade connector on it.  Is it for this purpose?  I was assuming
that this tag would be used to run the mains earth to, and it dosnt look
like it was designed for multiple wires.  Does it even matter so long as
everything is, in some way, connected to the mains earth wire?  If this is
the case, this is making me think: the enclosures of most items are grounded
metal.  Why is the ground always run to a common point, and not just to the
nearest piece of metal?  I feel as if i may well be completely off track
here, but i know very little about mains power and grounding.


And also on the fuses... The literature suggests a 1.5A slow blow EXT. fuse
for 240V applications. Is this suggesting the fuse that i should put in my
plug (the one that goes into the wall mains socket)?  Or elsewhere...?  The
confusion, as 1.5 amp is lower then anything commercial ever uses.

Cheers for reading this.  I realise these are somewhat basic questions.. And
not specifically related to sdiy either i guess...  I could make guesses on
most, but id like to be sure : )


Julian


Oh, one last thing.. i see an optional cover in the farnell catalogue.  At
£12, is this realy just a plate to cover up the circuitry of the psu?  In
which case, with the psu mounted in the rear of my modulars enclosure, it
realy isnt necisary, right?