Re: Turn on Apple to preserve it?

[Mike Willegal <mike@willegal.net>]

Yes there are plenty of kinds of DC to DC converters around, but at 
least for initial prototyping, it would be faster to put together, if I 
didn't need to design a onboard power supply.  In any case, I also have 
to think about ground loops.  I'm not sure if typical USB 
implementations optically isolate the USB bus from the rest of the 
circuit or not.

Regards,
Mike Willegal

Linards Ticmanis wrote:
> Mike Willegal wrote:
>
> > So what are the restrictions on the early Apple supplies.  I've been 
> > thinking about the implemenation of a USB-Disk II interface.  One of 
> > the issues is a power supply for a Disk II  (+5/-5/+12/-12).  One of 
> > easiest solutions would be an Apple II supply, but I'm not sure if 
> > there is enough current draw from an idle Disk II.  Any thoughts out 
> > there?
>
>
> -5 is not needed at all as far as I can tell from the schematic, and -12 
> only to bias the differentiator in the mc3470 amplifier, so current draw 
> should be tiny.
>
> Aren't there small components that can make -12 from +12?