In article ,
Andy Evans wrote:
I'm just finishing off a basic power supply for a computer style CD
player to use as a stand-alone CD player with my hi-fi. I've built it in
a computer PS box, and so far it consists of two 20VA trannies,
configured with 6v and 12v secondaries. I've mounted a 78S05 and a 78S12
on heat sinks about 1.75 ins square bolted to the case, and have used a
bridge rectifier (100v, 3A) and 4,700uf cap for each supply. Before I
hook up the voltage regs, can anyone suggest any preferred circuits,
parts, part values etc for the purpose (cap values before/after the regs
etc, or other solutions)? I'm assuming this won't run too hot but again,
suggestions welcome. The 20VA trannie for the 12v supply is a bit tight,
but I just happened to have some. Andy

I'd normally use a 9 volt transformer for a 5 volt regulated supply using
a 7805 - although since the transformer is rather under run you might be
ok. But I think you'll have problems at 12 volts. I'd use 15 there.

4700µF should be fine for up to one amp. Add a 100nF ceramic disc in
parallel. On the output of the regulator, have a 10µF 100nF and a 1N4001
diode (cathode to negative) in parallel, to ground. Also another diode of
the same wired input to output of the reg, reverse biased, cathode to
output. The diodes just help protect things if you do something stupid
like me.

If checking the PS before use, remember to load it to at least 5mA.

--
*Someday, we'll look back on this, laugh nervously and change the subject

Dave Plowman London SW
To e-mail, change noise into sound.