I have two 3T machines and neither one has a tape drive.
99% of the RS232 problems I have dealt with are port configuration issues with the PC. There's a bunch of info out there on configuring your serial ports for RS232.
If you aren't using a serial port, well, good luck. If your PC lacks a serial port add one to it. If it's a laptop, well, that sucks.
They make port tester things with led's that light up when stuff is happening. pretty handy for this kind of stuff.
RS-232 is not a single standard, it is a set of options that got mangled over the years.
You need software on the PC, such as the previously mentioned Hyperterm.
You need a port on the PC. There a plethora of usb to rs-232 to usb adapters for around $20 that work well.
You need a cable. With the right pins connected, and the right ends (male vs female). Often the usb adapters are 9 pin rather than 25 pin so you might need to take that into account.
These pins are transmit, receive and signal ground,
On a 25 pin connector, pin 7 is ground. On a 9 pin connector, pin 5 is ground.
On both, pins 2 & 3 are transmit and receive. On some devices, 2 is transmit, 3 is receive. On others 3 is transmit 2 is receive. Regardless transmit on one end needs to connect to receive on the other. So if transmit is on the same pins on both ends, you need a “crossover cable” that connects pin 2 on one end to pin 3 on the other end, and 3 to 2.
Once cabling is correct, you have to get PC software configured: port, Baud rate, data bits, stop bits and parity.
You should be able to google more info on each step.
You will not harm anything with having the cable wrong or the software configured wrong. It just won’t work.
If you get nonsense characters, it usually means a baud rate/parity/stop misconfiguration.