hello Ricardo. If you're able to type intput to the serial ports, but not able to see output, I'm guessing you're having a cabling problem, rather than a hardware problem with the SS4. What's probably happening is that when you unplug the keyboard, the firmware is putting the console on the serial port, but since no output is coming through, your'e not seeing it. Do you have other serial cables you can try? What about making a cross over serial cable between one of your working SS10 or SS20 machines and the SS4 and building and installing the comms/kermit package on the SS10 or SS20. I like that package because it allows you to fiddle with the serial port settings in real time to get things up and talking. I'm thinking that will give you a working bi-directional connection to the SS4 serial port, plus a configuration you can use to reverse the connection, should the need become necessary for one of your other machines in the future. Hope that helps. -Brian