Hi Folks,

Picked up an Atari 520 STFM today. And before turning it on I obviously wanted to check inside. Doing that revealed a few oddities and mods that I need help identifying before I turn this on for the first time.

The first is I don't think this is a 520 board. I think it's a 1040 board. And it's been upgraded with more memory. It has 16xMB81256 chips and 16xTMS4256 chips. I think the "TMS" row is stock and the upper "MB" row was added by someone. Any Atari experts can confirm?

Also there's an A/B switch added on the side of the computer. On the inside there seems to be a chip third party chip and some pretty intricate work done with bodge wires to the board. I thought maybe it was to boot from the internal drive or from an external drive, but I'm just guessing based on the position of the switch. Anyone have any ideas?

And lastly there's another mod, I'm not sure is a mod or stock. The wire runs from the video circuitry? - to the video modulator. Is this stock or a mod someone can identify?

This is my first experience with an Atari ST so I'm clueless to this computer. Appreciate any feedback on these findings.

Thanks.