Put an oscilloscope on what you think is the transmit data pin. You should see the board trying to transmit.
If you don't have a CRO, slow the baud rate down as much as you can and put a LED on it.
Then put the CRO on the RX pin and see if the terminal program transmits on there. Compare the bit widths.
Make sure you don't have two driven pins connected together (TX connected to TX etc).
Make sure the terminal program is configured with no flow control. It may be set to want the other signals (CTS, DTR and the like).
Does the Tower board provide these signals? Are they not-connected, driven from the chip or driven from pullup resistors?
The DB9 connector has three pins you care about. The other ones are there to cause trouble.
Try shorting TX to RX on the cable and see if the terminal program with display what you type (testing it and the cable by using a loopback).
Tom