PDP-11/44 problem - RUN stays on

Yesterday evening I had a look at my sick 11/44. The notes I had kept said that the VT100 displays "?CP didn't start". I already knew that this is the typical bus hang condition, so I opened the BA11 box. I was surprised to see the FP11 board (I did not know I had that one), but I also saw that the last slot of the CPU backplane has a G727 ... I remember that in that quad slot had been the TU80 controller, sure an NPR device. So, I pulled the G727 and inserted a G7273, and pushed all other boards firmly into place. A few boards actually moved a little (say, 1 mm). Powering up ... the 11/44 shows the ">>>" prompt and is responsive, but I was too lazy to unlock the heads of the RA81 and tension the motor/spindle belt. The RA81 is the boot device for the 11/44. The system has an RL02 so I tried >>>B DL0: but then the 11/44 shows on the VT100 "no such PROM" (IIRC, or something close like this). OK, I was glad not to see "?CP didn't start" anymore, and I turned off the machine. Half an hour later I had thought of entering the boot code for the RL02, so I turned the 11/44 back on. However, ... besides the DC ON light, the RUN light stays ON too. I am sure the RUN light should go OFF. It does not matter if the switch is in the HALT or CONT position at power up. The VT100 only displays: (Console V3.40C) (Program) and nothing more, no ">>>" prompt anymore! Also, the FAULT lamp on the RL02 drive stays ON. In the normal behaviour, the FAULT lamp is OFF, and if you toggle the switch to the "BOOT" position, the FAULT lamp will flash ON briefly. The TK50 (also connected to the 11/44) flashes the red push button lamp and after a few seconds the red lamp goes OFF and the green LED goes ON. Now, in its faulty state the TK50 still behaves the same when I push the switch to the BOOT position, but the RL02 drive keeps the FAULT light ON. As the FAULT lamp stays ON of the RL02, I am *guessing* that the 11/44 does not issue a "reset", keeping the CPU hung, and the RL11 controller ...? Where do I start? What are the obvious things in this machine? Don't read this line Tony. I have 2 spare set 11/44 CPUs. thanks for any hints! - Henk, PA8PDP. This message and attachment(s) are intended solely for the use of the addressee and may contain information that is privileged, confidential or otherwise exempt from disclosure under applicable law. If you are not the intended recipient or agent thereof responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication in error, please notify the sender immediately by telephone and with a "reply" message. Thank you for your cooperation.