Re: -5V on IIgs

[Don Bruder <dakidd@sonic.net>]

In article <1172990381.645943.15390@64g2000cwx.googlegroups.com>,
 "James Littlejohn" <narguthru@yahoo.com> wrote:

> On Mar 4, 12:25 am, e...@FreeNet.Carleton.CA (Michael Black) wrote:
> > "David Wilson" (mcs6...@gmail.com) writes:
> > > On Mar 4, 4:08 pm, "James Littlejohn" <nargut...@yahoo.com> wrote:
> > >> I have been going over the schematics of the IIgs, and was wondering
> > >> if the -5v line goes to any thing besides the RGB output chip? I can
> > >> not find anywhere else where it is used. Will the computer run without
> > >> this feed?
> >
> > > You missed a couple of places. Page 4 UB15 and UB16 (serial output
> > > driver chips), Page 7 pin 34 of slots 1-7, Page 8 UL14 pin 11 (sound
> > > chip).
> >
> > > I would not recommend it.
> >
> > On the other hand, for a long time any drain on a minus voltage in a 
> > computer
> > has generally been very low.  So you need it, but not very much of it.
> >
> > LIkely a string of AA's would do fine, or if one wants to get fancy,
> > a dc to dc converter to convert the +12 or +5 volt line to -5v.
> >
> >    Michael
> 
> Michael,
> You would not hapen to have a schematic for a dc-dc converter for the
> -5v, would you?

The "quick and dirty" method:
Get a 7905 regulator (-5 volts regulated output - 78xx and 79xx series 
regulators are good to just under an amp)

Wire the input of the regulator to ground. Wire the ground of the 
regulator to the +12V line. (hook it up to the supply "backwards") Now 
use the output to feed the -5V line.

Presto!

You can do the same, using a 7805 regulator wired normally - ground to 
ground, input to +12V, output to +5V line - for your +5 volt supply.

-- 
Don Bruder - dakidd@sonic.net - If your "From:" address isn't on my whitelist,
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