The trick with the C64 is that it
requires both 9V AC and +5V DC. (I've considered frankensteining
together 9V AC and +5V DC wall-wart adapters onto the same DIN-7
cable, but it just feels so very very wrong).
Like this:
<http://c64.digitalscream.com/Slappy/slappys-power-supply.JPG>
The power supply in that photo caused quite a stir in the C= community
earlier this year. You can read more about the sordid affair here:
Aha! Well, I'm glad that you pointed this out. It seems like the
wall-wart path is a false economy.
Wall-warts are often recoemnded in electronic magazines over here as
being a safe way to get the low voltages for the projects from the mains.
Personally I regard them as about the most dangerous thing around. I've
yet to see one with proper mains fusing, most don't have output
current limiting, and so on.One common type sold in the UK has a 4-way
cross-shapped plug on it (3.5mm jack, 2.5mm jack, 2.1mm coax, 2.5mm coax)
with separate 1.3mm coax ('Walkman' plug) and a 9V battery clip on the
same cable. It's very easy to get a short-circuited output if those
conenctors touch each other. YEs, I've had it happen, and the wall-wart
got hot enough to melt it's plastic case (and would have got even hotter
if I'd not unplugged it!).
I'd much ratehr trust one of my home-mae PSUs, in a die-cast metal box
with over-rated components, mains and LT fuses, etc.
-tony