A quick follow up. I did the above without the bottom RAM board in
the stack. When I attach all of the boards, then the little EF3->Q
mirror program works (somewhat--unshifted characters are not as
expected). Sadly, still no sign of life with the TMSI Basic+IDIOT/4
EPROM in place.
I don't know why the presence of the RAM board should have any effect.
Interestingly, I notice that after powerup, the clock doesn't seemto
start up until the right-hand switch on the display board istoggled.
On reassembling the unit, I "discovered" the label- ON/OFF :-)