I have an old video game console that outputs an RF video signal. My plan is modify the console to output composite video and audio so I can connect it to a device that doesn't have an analog tuner in it. My thought was to use a 3 or 4 conductor 1/8" phone jack (audio is mono so I don't necessarily need separate left/right audio lines) like you might find in some portable DVD players or camcorders.
The problem is that this console, a 1975 Atari Pong, has a power plug (called the "battery eliminator" as it was normally powered by 4 D-cell batteries) which uses a 2 conductor 1/8" phone jack. I'd like to protect the circuit from someone plugging in that 1/8" power adapter into the A/V jack. How would I do that? It seems a few diodes would be in order, but I'm guessing the forward voltage of the diodes would degrade the video and audio signals. Would that be the case? And if I could use diodes for this, would I need something special, like a low forward voltage, high frequency diode? Or is there another way? Maybe PFETs?
The simplest solution would be to not use the 1/8" jack for A/V and instead use RCA connectors. Maybe that's the way I'll go, but I'd still be interested to hear if there's a solution to using the 1/8" jack.
Thanks