24v vehicle - 12v radio ???

[nohandle]

I have a 24v vehicle and I have a 12v cb radio. I bought a 24v to 12v step down converter and thought I was all set. The step down converter has a common ground. I conected vehicle 24v pos to sd conv and 12v pos from conv to cb radio. sd conv has only one ground terminal and I conected neg from radio to it and from same terminal grounded to vehicle chassis. At antenna base I grounded coax like you would normally on your 12v vehicle. I noticed what looks like a capacitor discharge from the pl-259 conector to radio when I disconected coax from radio after being turned off. Also I noticed my radio while running the display would sometimes flicker (but not when in my 12v vehicle). After a short period of time the sd conv went bad. I have a new sd conv now and have not hooked it up yet. Am I missing a piece of the puzzle or faulty equipment or what? Volt meter showed 25.8v input and 13.8v output, discharge from coax was not mesureable. I need some help on this one guys, thank you.

[cbrown]

To me it sounds like you may have had a faulty ground somewhere in the power supply chain and the negative supply was coming in though the PL-259.

[nohandle]

Thank you for your help, I will double check my grounds before I try again. I am not missing any other equipment to do this type of conversion though right?