30 Jun
2008
30 Jun
'08
6:02 p.m.
On Monday 30 June 2008 20:52, Eric Smith wrote:
I wote:
Well, if you were trying to operate the 9VAC and the regulator for the +5VDC
off the same winding, you'd run into some trouble there, I think...
Why does it require isolation between the 9VAC
and the +5V DC? It's not
obvious to me from the schematic.
Roy wrote:
The 9VAC supply is fed into a voltage doubler to
derive the regulated
+12V and a separate +5VDC supply, and I don't think that either of those
9VAC lines can be grounded.
Neither side needs to be grounded. The C64 *already* has a bridge rectifier and 5V linear
regulator powered
by the 9VAC input to produce an auxiliary 5V supply, so I don't see why
building an external power supply using a transformer with a single 9VAC
secondary, and a bridge rectifier and 5V regulator (linear or switching)
would be a problem.
Because they really need to have those two +5VDC supplies separate and
independent of each other. That's the way the thing was designed, and as
much as that company was into cost-cutting and shaving wherever they could,
to the extent possible, I think that if they could have omitted that somehow
they would have.
However, I haven't tried it, and don't accept
any responsibility for
anyone else trying it.
:-)
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
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