PDP-11/45: VT52 repair

Replacement oscillator arrived for the VT52, so spent some time getting it back going again. Things got much better with a stable timing chain, but some glitchiness remained -- tracked this down to the socketed microcode ROMS which just required a reseat.

Here you can see the new oscillator fitted (silver rectangular can with tie-wrap). The microcode ROMS are the four socketed chips towards the right in the picture. Interestingly, the schematic I have calls for 8 ROMS of half the size of the ones that are in here, and indeed you can see the unpopulated spaces for these on the board.