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: firstname.lastname@example.org > > [mailto:email@example.com]On Behalf Of ext Luca > > Di Pasquale > > Sent: 11 January, 2004 12:03 > > To: firstname.lastname@example.org > > 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, <email@example.com> Message was sent through the cbm-hackers mailing list
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