There's a great tear-down with lots of pictures at kevtris.org
I decided to pull my 2521G apart and replace the DS1220Y with a more modern device, the DS1220AB. I used the same speed grade: -200 (200ns).
It was easy to remove the screws and connectors to get access to the CPU board, but it was then discovered that the DS1220Y was soldered in. Removing it was quite the challenge, and was performed by a friend with much more experience.
Once (carefully) removed, the SRAM was read using an EEPROM/EPROM/SRAM programmer and saved it to tek_ps2521g_sram.hex.
WARNING: I don't know what this file would do when placed in another PS2521G. It might smoke your supply .. but I doubt that.
I installed a socket for the new DS1220AB, programmed the part using the programmer, and installed it. After re-assembly, the power supply powered up and worked like a champ! We're good for a few more decades ...