There's an uncomfirmed rumour that the proper
Acorn Atom brick is the
same as the Dragon 32 one, just with a different lead (and unused taps
on the transformer presumably!).
Considering the Dragon brick has 2 AC outputs (14-0-14 and 8.5V) and the
Atom brick has a 9V DC output, I think that's highly unlikely!. The case
might be the same, but the internals are different.
In the six or so Atoms that have passed through my hands though I've
never had one with the original supply, so I can't confirm that :) (All
of mine have either been kits - and I assume the PSU was optional - or
previous owners have bypassed the regulators and used a more capable
supply)
The reuglators in the Atom were marginal at the best of times, and it was
a semi-official mod to make the machine run off an external 5V supply
bypassing the regulators.
I'm not sure what voltages the D32 uses internally. I've been told that
the D64 regulator board is different to the D32 one even though it uses
the same brick - so it's possible half the outputs of the brick aren't
even used in a D32...
The Dragon 32 needs +5V (obviously), +12V and at least one of -12V and
-5V. AFAIK all the outputs from the brick are used. The D64 PSU board
IIRC includes at least part of the serial port circuit (not present on
the D32), which is presumably why it's a different PCB.
-tony