I had the idea of building a small TV using a PSone screen.
Now I know how to add AV jacks to the TV, thats pretty simple, but what if I wanted to watch actual TV? I don't have cable or anything, but I get a few channels with an antenna.
What kind of circuit board would I have to build to make this work on a PSone screen?

you would need a tuner box with composite or RGB (or svideo, but you arent PAL).
but why would you want to do this? TV sucks, and psone screens have way better uses anyway.

Mostly for fun and for a learning experience.
Also, there are some good shows on once in a hundred years and it will mostly be used for testing game systems.

Anyways, where can I find a schematic or some sort of guide on how to build one?

you did not just ask for a schematic.

As ridiculous as it sounds, yes i did.

try browsing instructables, i guess.

You could try taking apart one of those DTV boxes that used to be everywhere. I can't imagine they draw tons of power on their own.

Unfortunately, the equipment you get from the cable or satellite company is rented or leased (it's their property, not yours), so all you can do is hook it up to your contraption unmodified.

Yeah, if you used the internals of a converter box, many models have composite-out.

http://cgi.ebay.com/MAGNAVOX-TB110MW9-D ... 3a590cdc52

Or go to any best buy/electronics store and buy one. The internal pcbs are usually pretty small.