I've got a mellanox 4036e off of ebay, and while it gets an IP and I get a logon screen, I neither have a password for it, nor can I get any sort of access via the serial port. I've tried a cisco console cable, a null modem cable, a straight through cable, and switch pins 2 / 6, 2/3 and 2/4 and I can't get even any gibberish to show on the computer end. Is the switch bad?