The timing board is now nearly finished, save for jumper wires:

I’m pretty satisfied, although the real test will be how it cleanly it mates to the motherboard.  I recently got my hands on an original Mark-8 construction guide (thank you, Roy!) and found out just how much scanning distorts PCB artwork.  It doesn’t just change the scale, it actually skews the artwork.  This means in situations where you need parts to align, like the molex connectors that the boards stack onto, you need to check to make sure it all lines up, at least.  Being that these were my first ever homemade PCBs, I didn’t think to check that.  Ulp.

There are a few caps and a whole whack of jumpers missing; those will be installed later.  I’m not liking the new style caps at all — I think those will be revisited.  I’ll get into the whole caps affair in another post.

Having done a bunch of jumpers on my ASCII encoder, I know this will be the least fun bit of the whole project.  I will do them all on all four boards while I await the last parts.  For now, I’m sticking to main components (ICs, caps, diodes, resistors, connectors).

Also, as I mentioned, I’m using sockets for all of it.  This is one clear break from the prototype — from the photo it’s clear Don soldered all his ICs in directly.  For an experienced electronics engineer this is doable, but for a self-teaching novice using 40+ year old ICs, this would be the definition of insanity.  It’s just so much easier from a troubleshooting standpoint to be able to swap ICs.  So, that’s how that goes.  However, in keeping with the hobbyist/prototype theme, I’m just using what sockets I have lying around that look correct vintage, rather than trying to make every one the same.  I think that gives the unit a more earthy feel.

I’m also keeping an eye peeled for solder bridges, and even accidental bridges from the toner transfer/etching process.  The construction guide warns you about these, and indeed, they were the major thing that prevented my ASCII encoder from working right off the bat.

Anyway, we’re done here for now.. onto the ‘mainframe’ (motherboard)!