Sorry for bumping an old thread, but had some info to add that maybe a few may find useful.
The original battery from Catalyst Research is a non-rechargeable 3V Lithium Iodide battery. There were at least two styles of battery installed in 1240/1241 units, one that looks like an oversized coin cell, and another that looks like an oversized crystal can. Speaking from experience, I can say that the oversized crystal can type battery is of extreme risk of leaking and destroying the A09 board (among other things if left too long - experience talking here).
The battery in the analyzer (and almost certainly the PAK's too) can be replaced with a 3V coin cell without issue, there is no charging circuitry, and the battery is diode blocked to prevent accidental "charging". To make that more factory-like on the 3 analyzer chassis I recently serviced, I designed a small carrier PCB that matched the battery footprint on the A09 processor PCB, having a SMT CR2032 coin cell holder on it. I used my board router to produce the three I needed, but I just posted the full artwork and shared it on OSH Park if anyone wants to have some made (or download the artwork to fabricate it elsewhere). It is shared here -
https://oshpark.com/shared_projects/oAsZEWxr and you can simply use a bit of wire or single pin headers to solder it to the processor board.
To correct a bit of information earlier in the thread, the 1241 does not use a special CRT, it is a monochrome CRT with a color LCD shutter assembly (red and green filters) added in front of it, with a different CRT drive board and aluminum mounting panel, along with a different display driver board to support it. To the best of my knowledge, the rest of the hardware between the 1240 and 1241 is essentially the same, with firmware changes to the EPROMS on the A09 processor board to support monochrome vs. "color".
Finally, a question - has a full manual for the 12RC01 parallel/serial support pack been made available for download somewhere? I haven't found it yet, but haven't done an exhaustive search yet either.
Thanks to everyone for the wealth of information shared, and also feel free to pass along or share the battery retrofit board via the Tek 1240/1241 Wiki if you think it's worthy.
Cheers!
--Brad