From: Luca Di Pasquale (LucaDP_at_gmx.de)
Date: 2004-01-11 14:20:40
I agree with you, that project is definitely more complex and therefore more prone to failure, and failure could mean, as you also wrote, a c64 less on earth! I only meant that is possible to adapt it to work with NTSC machines. Yet, I would like to use a pc PSU and get rid at once of all the C64 and disk-drive PSU's laying on my floor: has anybody already experienced such a solution? What are the pros and cons, concerning implementation and ease of use? Ciao, Luca > 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. Message was sent through the cbm-hackers mailing list
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