29 Jun
2008
29 Jun
'08
6:24 p.m.
I'm sure most everyone who has ever used a C64 is aware of just how
phenomenally bad the Commodore power supply is. I have only one C64,
but both of my spare Commodore power supplies have now failed, taking
a few 4164 RAM chips with them (thankfully, I have replacements!).
Does anyone know of a commercially available replacement power supply,
before I go off and build one? A linear supply would be trivial to
design, but I've never done a switching power supply, which I suppose
would be greatly preferable. The trick with the C64 is that it
Making a switching supply to give a 50Hz or 60Hz AC output would be
decidedly non-trivial (and IMHO not senisble here). The obvious way to
get that output, given that it's unregulated, is straight from a mains
transformer secondary. A second secondary (!) on the same transformer can
be used to produce the regulated +5V line, by rectifying, smoothing, and
regulated it. That regulator could either be a linear or switching one.
I know the PSU for my C128 does exactly that (that supply is not potted,
it was possible to access the fixing screws and take the case apart). It
uses a fairly simple swithcing regulator cirucit.
Switching regulators running off the output of a mains transformer ae not
that hard to design. Firstly there's no isolation to worry about (the
transformer takes care of isolating the final 5V output from the power
line). Secondly, there are no lethal voltages around (you're staring
from, pephaps, 12V AC). And thirdly, if something does fail, the fault
current is likely to be a few amps, not a few thousand amps.
I am pretty sure any of the single-chip SMPSU controllers, an external
chopper transistor, flyback diode and inductor, and some R's and C's
could be used for this.
-tony