I have one very similar, probably same age but a 2400 or 2500 I believe. It worked when I put it in storage and then didn't work after that. I wasn't aware they didn't power up when plugged in the wall but with no battery. That's good to know I might just need batteries!
My non-rackmount SUA1500 was floating the battery voltage a bit high. To fix it I connected to the serial port and issue some manufacturing commands which could be found online. The serial port has a non-standard pinout (requiring some creative wiring) but it is fully-intelligent.
