I had been looking at the two serial ports on the machine for some time.
I know the back serial port is for a UPS. I also noted that on this forum, there is a hack for other terastations to enable this as a debug port with a bit of a soldering and board rework.
The TS3 includes a second serial port inside the front door. Given that few people have an old RS232 serial port on their computers (let alone the appropriate crossover) I decided to crack it open to see If I could hook up a TTL232 to USB adapter (you can find these on Sparkfun. Its the FTDI adapter (https://www.sparkfun.com/products/9873
I'll take some photos of the board, and the little hack (its pretty easy to accomplish, but you need a steady hand and good eyesight).
I'll upload them later.
With the hack done, I was able to connect up via serial terminal to watch the flash boot. You need to set the term to 115200, 8, N, 1 no flow control (we are only using two wires for data, and one ground).