[wasyoungonce (Brendan)]

Originally Posted by troypiggo

This is the regulated power supply I'm using. Does that help?

Sorry...linky broken

edit:

I edited the link & found it's the Jaycar 13.8V switchmode PSU.

I have a version of that...it's OK but not a great regulated supply. Mine squeals under loads.

I suspect that this is putting switching noise on the output line which is the cause of your trouble. You said running it straight from DC it's fine...you either need to use DC (batteries) or a better regulated PSU.

This is one of the reasons I don't particularly like switchmodes, the cheap ones can be ...very cheap in more than one way...I prefer the old stepdown transformer & discrete regulator outputs. Don't see many of them these days.


edit edit:
I meant to say..I use my small Jaycar PSU for things like DEW heater etc..not sensitive equipment.