Is the Serial.println copied on the ttl lines?

What I mean is, if i have a program running that is sending strings out to the serial monitor (through the USB) is the same data also present on the Tx line of the TTL on the arduino board (pin D0 on my nano)?

Yes. Pin 0 and 1 are connected to the bus between the MCU and the serial to USB chip.

If you look around the site, you can find schematics of every Arduino.

Yes, thanks. I was looking at the schematic and that what I thought. I'm Trying to debug a Max232 converter (TTL to Serial). Not seeing the data on the serial side of the converter though. Hum...

Turns out my console program was gimpy. restarted the console and now I can see the strings. Yay!