Why doesn't the tv recognize the ps2?

I just bought a ps2 slim new and modded, when i turn on the console nothing happens. The led is green yea, but i see no signal on AV (i checked the others too), at the beginning i hear a small sound (sounds like a small fan starting spin) that ends after a few seconds, that's all. Seller said me they've tested the console on an HD monitor so the problem could regard the setting they did, but i have just CRT at home so i can't connect the ps2 to a modern tv.. there's a way to change video settings from an old CRT? Or by the way, problem might not be this?