Well, I feel somewhat stupid, but the problem with the hung bus is solved.
The cause of it? no jumpers on the backplane to bypass the battery backup. The machine had a BBU regulator, but it was removed as I don't have the battery pack. So, after adding the 3 jumpers the NPG signal was cleared after a cntrl+halt and characters could be printed when deposited at address 777566 (with memory in the backplane). So, next step is to add a RL11 controller and see if it will boot RT-11. But that is for the weekend.... Ed -- Ik email, dus ik besta. BTC : 1J5fajt8ptyZ2V1YURj3YJZhe5j3fJVSHN LTC : LP2WuEmYPbpWUBqMFGJfdm7pdHEW7fKvDz
