PDP 8/e Problem

Hello, everyone, This weekend I decided to spend some time and fire up my PDP 8/e system. It's been a while, and figured it was overdue for a few hours of runtime. The machine has EAE, 2 8K DEC Core memory units, an 8K solid state memory board (12x8 1K static RAMs) the extended memory/timeshare option, a PC8E paper tape interface with a PC04 reader/punch, an RX8E controller and dual RX01 drives, and (not installed) an RK8E controller (currently busted) with two RK05 drives, and two M8650 serial I/O interfaces. It powered up just fine, and I toggled in a few little test programs. I couldn't get it to talk to the terminal (a Heathkit H19). Then, I tried a test program that runs the punch...it too would not work. Then, I toggled in a little program that uses the OSR (OR Switch Register) instruction, and it too wouldn't work...the accumulator remained untouched by this instruction no matter what the state of the switch register was. I did some other testing, AND and TAD work, as does ISZ, and as many of the group 7 operate instructions that I bothered to test. DCA also works fine, as do JMP and JSR. I could load extended address from the front panel, and address memory beyond 4K with no problems, so at least the extended memory part of the ext. mem./timeshare option was working. I also noted that the HLT instruction doesn't work. So, IOP instructions, OSR, and HLT are on the list of instructions that don't work. It appears that these instructions just act as a No-Op. I tried stripping the system down to just the CPU, EAE, 8K of Core, and the console async. interface, and it still behaves the same. It seems like the instructions that aren't working are those that would be trapped by the timeshare option, but with that board removed from the system, the fact that the behavior didn't change is of concern. Anyone have any ideas what might be going on? Thanks in advance for any help. Rick Bensene