Thanks for all the help. I suddenly got very busy and haven't had time to take my A4000 apart. I lost several eBay auctions for an A520 and this morning bid on a DCE Flicker Magic internal scan doubler, left for work, and when I came home was surprised to find that I had won it for a little more than the minimum bid so when it arrives, I will take the A4000 apart and start working on it again. Once again, thanks to all who have posted their advice.
An easy way to test if the 68K is responding (thus the CPU card working) is to keep pressing the CAPS LOCK key - the LED should blink on and off as you press the button.
Keep pressing it. If it eventually stops toggling from on and off then the CPU is not responding.
If the CPU is working, the LED will keep toggling on and off for as long as you keep pressing the CAPS LOCK key.
