[geeks] Voltage regulators don't!

[wa2egp at att.net]

> Next up, I'll try adding some ceramic disc caps here and there - even
> if I'm not dc connected to anything, body capacitance is still present.
> The environment is probably rather electrically noisy, but I have
> trouble seeing how picking up additional noise onto the power input
> could *stabilize* the 7805, so I'm currently guessing it's stray
> capacitance that's responsible.  (I tried switching out the 30000uF
> filter cap for a 470uF cap, in case there was some funky resonance
> going on; no difference.)

I've seen circuits with those chips and they had 0.1 - 1.0 uF caps on the leads to stop "noise".  I think that there may be a high gain circuit that might take off under certain conditions and that might cause all that weirdness.  I once had a supply that not only delivered reguated voltage but could also be used to tune front end of FM radios. :)

Bob