PDT-11/150 down

Well, this is my first post to the list in quite a while; most of you may not even remember me... but I have been lurking. Now I have a problem I need help with. I have a PDT-11/150HC, the dual drive model with 32KW and the 3 extra serial ports. It had been working fine, up through last year, when I stored it. I was working on another project, building a PDP-11/53 from a DECServer 550 (like Jonathan Engdahl's) when I needed to copy some floppies. I brought out the trusty old PDT, and of course, it wouldn't work. I am using a VT420 with DECConnect wire and shells to talk to the PDT. The VT and wires are all known good, tested with other equipment. What happens is that when I turn the PDT on and type the 2 "@" characters to set the baud rate (4800), the #2 led properly goes out, the RUN led comes on, but NOTHING comes back to the terminal. Thinking that I needed a NULL MODEM in the cable, I put a MMJ crossover connector block between the terminal and the PDT. Strangely, I had exactly the same results - nothing out on the monitor - with TX and RX swapped how the heck does this happen? As I recall, the usual response is something like "Press B to Boot". In any event, pressing "B" does nothing either.

I have performed the self test with the lid off and modules elevated and the result was that the first 4 LED's on the Intelligence Module came on. This is result #17, indicating that either the DISK Controller Module or Cable G1 has failed and need to be replaced - impossible, at least in the case of the Disk Module. Besides, what does this have to do with no response on the terminal?