TS-RXL Beeps, Error light on, gibberish on display

[1000001101000]

Sounds like you're more skilled at that piece of things than I am.

I've done similar with a multimeter and found that a ~1v reading is sometimes a 3.3v volt data signal showing lower due to relatively low overall duty cycle. I would expect a clearer signal on an oscilloscope though. Thinking back I think even with the multimeter I would see 3+v spikes if data is actually being sent. You could move forward assuming that is the data line and see if you get any output at all.

It could be that we're learning what happens when the overall system is under volted or something of that nature. I've never gotten gibberish on a display but I've also never had a power supply partially fail on one of these.
You could probably take a look at the output of the power supply to the board and see i the 12v/5v connections seem reasonable or not (taking all appropriate safety precautions and under the supervision of a licensed professional etc). 

[BillP]

Thanks for the thoughts. The power supply rails are fine - I had hoped there was a fault there, I could probably mend a power unit but it's unlikely I could fix the main board.

I just noticed that there is pattern of pads on the main board that looks like it would fit a nine-pin serial-port connector. I'll see if there is anything on the data pins of that.

Bill.

[1000001101000]

Good idea.

I've got some closeups of the board for the non-rackmounted devices with the serial port populated which might help:
https://buffalonas.miraheze.org/wiki/Main_Page

The serial port on those devices works (and very helpful when building custom kernels/installer images)