Gianmario.Scotti_at_nokia.com
Date: 2004-01-11 12:11:10
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
>
>
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>
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