PDP11/23 More dumb questions

Thanks all for the advice on the BA23 110/230v power switching. I've done that now and powered it up. I have a VT220 terminal that is functional as far as I know and connected to a random serial connector on the PDP, one of 6. Unfortunately I know nothing at all about PDP's or VT's. Anyway, I start the VT220 before the PDP and it gives a message VT220 Ready. I power up the PDP and basically get nothing at all. The only sequence that gets any response is hitting the halt button. The terminal then says: 165262 @ When I hit the Restart button after that nothing happens for about 2 minutes. Then an "&" prompt appears. Nothing I type in gets any response after that. Typing "help" gets no response. The machine is in a BA23 case and was a PDP11/23 I think, but has a PDP11/73 CPU upgrade. There is a full height ST506 hard drive reputed to be 30Mb in size, which spins and makes all the right noises. It was last operational about 5 years ago and was part of a Cybermation laser cutting system. I have no idea what OS would have been installed. I have no docs or media. Any suggestions? Thanks, Hans