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.
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