The 4500 was laid out for either RS232 using a LT1181ACN or a Sony 9pin Video format, using a LTC490CN8. There should also be a 3*8 header to select them – you will need a row of jumpers on the right side for RS232.
The Sony format is not implemented, the RS232 might be. See if there are SETUP menus for baud rate etc. If not, you are probably out of luck ..