From: David Wood (jbevren_at_starbase.globalpc.net)
Date: 2004-01-12 12:47:19
The primary reason for separate windings, as far as I know, is to get
isolation between the +5 ground and the 9vac. The SX-64 user port is known
for not working with certain devices because it's not isloated like the
breadbox psu is.
-David
On Mon, 12 Jan 2004 Gianmario.Scotti@nokia.com wrote:
> I actually knew that the transformer in the original C-64 PSU has a transformer with two windings, but I am not sure that's really necessary. I think a single winding would be adequate, given enough VA of the transformer. If that's not the case, I'd like to hear why.
>
> In any case, it's really trivial to use two windings instead of one, in the design I presented. It doesn't increase complexity at all. When I get home I'll prepare another schematic, to work with commodore's original transformer.
>
>
> cheers!
>
>
> mario
>
>
>
>
> -----Original Message-----
> From: owner-cbm-hackers@cling.gu.se
> [mailto:owner-cbm-hackers@cling.gu.se]On Behalf Of ext Hársfalvi Levente
> Sent: 12. January 2004 11:50
> To: cbm-hackers@cling.gu.se
> Subject: Re: C64 power supply replacement
>
>
> Hi!,
>
>
> Gianmario.Scotti@nokia.com wrote:
>
> > A transformer doesn't have separate taps for 9 V AC *AND* regulated 5 V :o)
> > And I did put a fuse in the 9 V AC line in the schematic.
>
> The transformer in the C64 PSU has two independent secondary circuits, 9V AC
> each. One of these circuits is rectified and regulated (5V DC), the other is
> just brought to the C64 (only a fuse is used).
>
> See these schematics:
>
> http://www.funet.fi/pub/cbm/schematics/computers/c64/c64-powersupply.gif
> http://www.funet.fi/pub/cbm/schematics/computers/c64/c64extps.gif
>
> As you see, the two outputs (5V dc, 9V ac) are fully "independent" in the
> original PSU design. They aren't grounded together in the PSU.
>
>
> Regards,
>
> L.
>
>
>
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>
>
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>
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