Trying to fix an Odyssey^2

I recently purchased two O2s from a friends of mine along with a bunch of games. One of them works perfectly. The other, however, has audio but no visual. I turn it on and I can only hear it working. I opened it up and tried it with a newer composite cable, but that had the same result. Any ideas how to bring visual back?

You could try to exchange the RF modulators (metal box) to see if that makes any difference.