using new technology on old machines. Was: PDP-12 Restoration at the RICM

Mark J. Blair nf6x at
Mon Jun 15 15:48:12 CDT 2015

> On Jun 15, 2015, at 11:54 , tony duell <ard at> wrote:
> Ah, 'there's not the time to do it properly, but there is the time to do it again'.
> Why not do it properly first time? What is the rush in bringing up a classic computer?

Sorry for yet another reply, but I didn't think of this until just now: When I was working on getting tu58em functioning with my 730's console code a couple weeks ago, a few folks recommended that I build an Arduino-based emulator that has been known to work well. But I didn't, because I didn't have that particular kind of Arduino board on hand, and I wanted to get it working that weekend instead of the next one. And I did. :P

> 'Full stock of TTL parts' ??? You make it sound like I am suggesting using lookahead carry generators,
> parallel multipliers, Excess 3 to 1-of-n decoders and the like (all of which exist(ed) in TTL). No, I am suggesting
> using some very common counter and gate ICs.
> How are you going to fix a TTL-based machine like your 11/730 without spares and without knowing
> what the ICs do?

The same way I got my HMMWV running back in 2000. I had quite a bit of parts and tools on hand already from my previous work on my M543A2, and plenty of manuals to study. Some things I fixed with what I already had on hand. And when I found that the injection pump needed rebuilding, I took out the pump and brought it to a local Stanadyne shop. And I ordered a replacement radius rod end after I determined I needed it, not before. I had a lot of 1/4"-20 grade 8 hardware in my junk box already for misc. mechanical repairs, but I still had to order some more for sizes I hadn't encountered before.

Back on the 730, I don't have most of the parts you mentioned on hand already because I've only gotten into retrocomputing within the last 2 years, and I've spend most of the last 30 years keeping with the times. Hint: I haven't designed a through-hole board at work since the early 1990s, and I didn't use perfboard the last time I built a GPS receiver the size of my pinky fingernail (not an exaggeration). ;)

Mark J. Blair, NF6X <nf6x at>

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