I have identified the ICs for you:
http://www.hddoracle.com/viewtopic.php?f=175&t=2693http://www.hddoracle.com/viewtopic.php?f=147&t=2695I would connect the adapter to a USB port and use PuTTY to talk to it. Connect the Tx and Rx pins together and then type stuff on your keyboard. You should see your typed characters being echoed.
You may need to install Prolific's USB-TTL driver.
If you don't see anything, then create a 1MB file consisting of the character "0x55" or the uppercase letter "U" (alternate 1s and 0s) and then transmit this file to the adapter's COM port. Select the lowest baud rate and then trace the signal path on an oscilloscope.