The first machine I really worked on, as a schoolboy, was a DDP-516. One of the most fascinating aspects for me was that I had the schematics of the CPU; this made it so much more engaging than the 6502- or z80-based machines that were the alternatives available to me.
Scanned manuals containing schematics can be downloaded from the Documentation page on this website. (The DDP-516 schematics are in DDP-516 General Purpose Computer Volume III. The H316 schematics are in H316 General Purpose Digital Computer Instructions and Logic Block Diagrams.)
Schematics for the H316, drawn using a schematic capture package, may be downloaded from here.
As part of an ongoing effort to get a really solid "primary" reference of the detailed operation of these machines, I've now got to the point where the schematics of the H316 can be converted into a Verilog netlist allowing them to be simulated in a modern hardware simulation package, as described here. While the actual hardware arguably provides the definitive reference, the gate-level simulation comes a close second, and it is much easier to study a simulation where all of the internal nodes can be probed.