I have a IIe which always boots to the system diagnostic (garbage screen followed by "System OK"), no beep. My understanding is that this is traditionally caused by either a bad keyboard connection or a stuck key. However, I've tried:
- Replacing the keyboard with a different one
- Reseating both ends of the keyboard cable, replacing the keyboard cable with a different one
- Trying the keyboard and cable in another IIe (they work fine)
- Mashing the keys a while to toggle any that might have been stuck
- Removing all expansion cards and trying the above steps
With no luck whatsoever. The machine still boots to the system diagnostic, and the keyboard appears responsive - its power light turns on and if I press the apple key after the diagnostic completes it goes back to the garbage screen. What else could trigger this state?
More context: This machine has been working for quite some time. Earlier today I installed a Mockingboard in Slot 4. After that, I was hit with these symptoms. After taking the machine apart, it started booting up again after I removed and reinstalled the keyboard, so I assumed the cable was loose on the keyboard side. After I confirmed everything was working with all the expansion cards reinserted, I put the top of the case back on - and was back to booting to the system diagnostic. I've removed the case and done all of the steps above with no luck - am I missing anything else obvious that could trigger the system diagnostic?