Spent some time going from a pile of Atari System 2 boards I accumulated over the years as I had 720 in the shop that I was working on. I didn't have any experience with these boards, but figured some had to be easy fixes and actually most of them were things like damaged traces or a bad socket, was surpised how many I got running. Here's some of the repairs, look out for broken crystals as well, I've seen them a few times on the video boards as they stand upright and get knocked off easily.
System 2 boards include 720, Paperboy, APB, Championship Sprint and Super Sprint, from what I've read they can be converted back and forth to some degree by swapping roms as well as the Atari Slapstic (security chip). Haven't tried it yet, but they CPU boards all look identical. I believe there were two versions of the video boards. Repair logs follow, enjoy.
Atari System 2 Repair Log
Super Sprint CPU (12/8/17) – Board booted to garbage on the screen, clock signal looked good, reset signal was low (normal) and data lines were moving. Checked program roms and ram, but they tested good in another boardset, which I expected. Was puzzled on this one as it seemed to be behaving normally based on other boards I looked at it. After some probing around found that 14.318 crystal had a broken leg, replaced the crystal and boardset booted fine.
Super Sprint CPU (12/7/17) – Board booted to garbage on the screen, clock signal looked good, but board was watchdogging. Checked program roms and ram, but they tested good in another boardset. Pressing on the TII processor during boot-up got the board to show signs of life. Replaced processor socket and board played fine.
Paperboy CPU (12/6/17) – Nothing on screen, just some white raster. Quick inspection showed some traces that were scratched. None were cut, but two were smashed together and shorted. Cleaned up the area, retested the board but still nothing. Clock signal looked good, reset line was watchdogging. Swapped program roms and rams into known working board to find bad 6116 at 6P. Board now boots up and plays but has a sound issue.
Self tested reported bad rom at 2D, replaced it but sounds were still off, but no longer reporting that error. Started swapping sound ICs and found bad YM3012 on row 8. Replacing that fixed the problem. Rom error 2D popped back during testing, replaced socket and it is started working again.
Paperboy Video (12/7/17) – Board booted with video issues. Swapping roms into known working board and found rom at 6T to be bad. Burned new rom to fix the problem.
Paperboy Video (12/7/17) – Lines in the “paperboy graphic” on the newspaper screen. Pressing on roms showed that it went away when I pressed on one. Removed rom, cleaned legs and reinstall to fix the problem (forget which rom it was).
Paperboy CPU (12/6/17) – Nothing on screen, just some white raster. Quick inspection showed some traces that were scratched. None were cut, but two were smashed together and shorted. Cleaned up the area, retested the board and it came back to life.
Paperboy CPU (12/6/17) – Board booted with random specks of garbage on screen. Removed T11 processor and reseated it, board came back to life.
APU CPU (12/6/17) – Board booted to garbage. While checking program roms, noticed that two were in the swapped in the wrong location, moved them back to the proper location and the board booted fine.