From: Ryan Underwood (nemesis-lists_at_icequake.net)
Date: 2004-01-16 00:06:06
I had a design proposed to me by a friend; advantage is that it is
easily built from Radio Shack parts but I would like some opinion on it.
- Start with 120V / 12.5VAC transformer
- Use voltage divider to derive 9VAC from secondary and send that
straight to the C64 (it needs no regulation, correct?)
- perhaps a bridge rectifier on secondary?
- Send 9VAC through a 7805 regulator set to 5V
- Filter ripple from 5V with a RC pair
- Zener protection on regulator output to prevent short failure damaging
C64
Lots of cheap parts. The question is, will it work?
On Sun, Jan 11, 2004 at 01:11:10PM +0200, Gianmario.Scotti@nokia.com wrote:
> I must object to that design. Not only is it more complex and expensive than the one I presented earlier, it also has an excellent chance of frying your C-64! Let's analize the circuit for a moment, shall we? The schematic is http://www.volny.cz/dundera/power_sch.pdf
>
> - it contains 2 integrated circuits and 6 (!!) bipolar transistors.
> - if ANY of the active components mentioned above barfs, you end up with a constantly positive or constantly negative +12 or -12 V DC instead of 9 V AC - and since you depend on the functioning of 8 active elements in switching mode, your chances are very good (or bad, depending on your point of view).
>
> Other disadvantages include:
> - Requires more conponents AND it still requires the PC power supply. It will be bulky AND it will be noisy (fans in the PC PSU)!
> - Produces a SQUARE wave instead of a sine, for the 9 V AC. I don't know about you, but I won't be powering my C-64 with a square wave, even if it survives the first few days.
> - The frequency of the wave is not steady, as it is produced with a simple RC element. Sure, it might work at the beginning, when you construct the device, but wait till it's a warmer day, or a colder day, or heck, if the humidity is much higher or lower....
> - The BD135/BD136 transistors are subject to considerable stress. They will definitely produce heat and will be a good candidates for crapping out one nice day.
>
> In comparison, the design I presented is much simpler, it will never fry your C-64 (it uses the 7805, which has protective circuitry to protect itself and the target, and it's virtually impossible to damage), it has only 1 active component (the 7805), it's silent (no fans), it "produces" a 9V sine wave, as the original PSU and at the correct frequency. The only active element to warm up is the 7805, which, as I already said, contains protective circuitry that saves it from overheating as well. The only disadvantage of my design would be that youneed a 220/9V transformer, but I suspect you could use the one from the original C-64 PSU.
>
>
>
>
> > -----Original Message-----
> > From: owner-cbm-hackers@cling.gu.se
> > [mailto:owner-cbm-hackers@cling.gu.se]On Behalf Of ext Luca
> > Di Pasquale
> > Sent: 11 January, 2004 12:03
> > To: cbm-hackers@cling.gu.se
> > Subject: Re: C64 power supply replacement
> >
> >
> > Just change a resistor and a capacitor (R1 and C1 in that
> > project) and you
> > will magically get the 60 hz needed on NTSC C64's (and
> > finally get rid of the
> > shitty C64 power supply!) :-)
> >
> > Ciao,
> > Luca
> >
> > > Remember that that is 50hz so in the non-PAL C64 your
> > clocks will be
> > > wrong including the CIA timers which get their frequency from the
> > > 9VAC.
> > >
> > > --Ray
> > >
> > > >For anyone looking at replacing a C64 power supply with
> > one from a PC
> > > have
> > > >a look at this web page;
> > > >
> > > >http://www.volny.cz/dundera/stuff.html
> > > >
> > > >This is the IDE64 home page however they have a nice
> > little DC to AC
> > > >circuit so you can power your C64 from the one power
> > source instead of
> > > >having one for ac and one for dc.
> > > >
> > > >I haven't built it yet so I can't say anything about it's
> > reliability or
> > > >design.
> > > >
> > > >Mike
> >
> >
> > Message was sent through the cbm-hackers mailing list
> >
>
>
> Message was sent through the cbm-hackers mailing list
>
--
Ryan Underwood, <nemesis@icequake.net>
Message was sent through the cbm-hackers mailing list
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