I currently own also an Atari 1200XL personal computer. The screenshots here demonstrate that it can run with no issues and boot into Basic. However, the keyboard is not working and we will review why down below.
I was online searching through the Facebook marketplace one day in search of some Atari components and possibly a replacement of the computer I own (the Atari 800XL).
I came across an advertisement on Offer Up where a guy was selling an Atari 1200xl. I figured it would be hard find anywhere else. So I drove a half hour from Phoenix to Deer Valley to check it out. Unfortunately he had no monitor to connect it to, but I could see the power LED showing it powered up. Only later when I brought it up, to my dismay did I learn that the keyboard did not work.
First it is necessary to do a power up test to ensure that the computer can boot up properly. So I connected it to my Commodore 1702 monitor and made sure to remove the Basic cartridge. It will produce the Atari logo to ensure the display is working.
Next I inserted the Basic cartridge. Some information about this may be important. The Atari 1200XL ROM kernal did not include Basic (at least my version does not). So it is necessary to obtain a Basic cartridge in order to boot the system. This was common for a lot of computers during that age.
Examining the keyboard cable
Here you can clearly see the Atari 1200xl computer case has been removed. The keyboard cable has to be removed as well as another connector switch (on the left) before you can see the internal components within. The cable is removed on the left by wiggling it out slowly as well as the smaller connector.
The Atari 1200xl torn cable
Closer analysis shows that the keyboard cable has been ripped from the attached board, which may explain why I get few keystrokes to work. This is going to likely require a complete replacement of the keyboard component. The opposing grey cable can be seen here as well.
This was likely torn when someone opened the unit. That is because the keyboard must be slowly opened when the case is pulled back or it can easily rip the cable from the board, which appears to be the case.
Here is yet another screenshot showing the opposite end of the cable (that connects into the main motherboard). It doesn’t seem to be damaged and the pins are not bent on the board, as to require any soldering that I can currently see.
I have yet to begin work on this unit as my time is restricted pretty often. However, I wanted to post this analysis review to get some feedback from this website to see if anyone else has experienced this and maybe have a solution that could save replacing the entire keyboard assembly.