Quoted from Ferret:
The 10+ LEDs may or may not be truly out. These are on a serial chain, so if one lamp fails, it takes out all the lamps downstream on that same chain. The chains are identified in the Lamp test with a designation like "2B4" -- that's I/O board 2, chain B, lamp 4. So for example, if you walk through the lamp test and find that 2B4 and all the following 2Bx lamps are inoperative, suspect that 2B4 or 2B3 is problematic, which could mean an actual failed lamp, or just that it's not firmly seated in its socket. Fortunately, if a lamp(s) are actually faulty, TimeBandit has produced replacements. These will also help with replacing your 5-element GI towers with individual lamps when you're ready to try moving to newer code.
I/O boards are probably fine. I wouldn't jump into replacing them.
You don't even necessarily need the new computer. Although we didn't do tons of testing with the production code builds on the older computers, there isn't much end-user difference between the PCs. The change was more about pricing and availability.
The thread that SunKing mentioned is long, but has tons of incredibly useful, detailed information by the cool cats who successfully revitalized machines similar to yours. Grab your favorite beverage and settle in for the read.
Good luck with your new game... you've surely got some work ahead, but hopefully it winds up being a game that you love.
I just fixed issues with the slingshot led not working properly because the « special » led was down which made all the line to fail. I’ve found this issue easily within the test mode so it was well done. Maybe your Led issue is the same thing.