[cctalk] Re: Back-plane wrap (was Re: Re: Antonio's call for donations (was LCM auction))

If I can find it, is anyone interested in a battery-powered wire wrap tool? Not sure of the diameter but it's larger than an IC socket, so I suspect that it is in fact for a backplane. Postage from Toronto. On Sat, Aug 31, 2024 at 1:55 AM Vincent Slyngstad via cctalk < cctalk(a)classiccmp.org&gt; wrote: > On 8/30/2024 7:25 PM, cz via cctalk wrote: >> To try and turn this thread around: I'm looking to make an extended >> memory controller for my pdp8/L. I've got a wire wrap backplane and >> enough cards to make it work but I've never done wire-wrap on this sort >> of scale. >> >> I've got an old Radio Shack Wire wrap tool and a lot of wire. Is there >> any sites that discuss how to do reasonable wire-wrapping? > Some of the older (single-sided especially) DEC back-planes were wrapped > with heavier gauge wire, which needs a different tool. The newer > back-planes seem to be wrapped with 30 gauge wire. You can tell the old > connector blocks, as the pins appear rectangular, rather then square. > > There are all kinds of opportunity for optimizing routing for distance, > cross-talk and and other esoterica. One thing that's worth doing, > though, is to wrap for a max height of two, and such that all the > connections (except possibly the last end of a given signal) are at the > same height. So, if A B C and D are to be connected together, you > connect A to B, then C to D (thus all at the lower level), then put the > connection of B to C at a higher level. This dramatically cuts down on > the amount you have to *unwrap* to fix something. Avoid situations which > cross the height boundary, because then you have to keep unwrapping > stuff you'd rather not, to expose the buried lower side. > > If you are wrapping by hand, you can be assured that you *will* make > mistakes and have to fix something. > > I predict you will also find that you are really sick of wire-wrap long > before you are done. These days, PCBs are inexpensive, and less error > prone (in the sense that you almost always end up with exactly the > connections in the netlist). OTOH, connectors are expensive and hard to > reuse when soldered to a PCB. So you've got to be really confident of > your netlist. > > You might consider investing in a tool where you pull the trigger to do > the wrap. You'll probably get a more consistent result, and > significantly fewer repetitive motion issues. > > Hope that helps! > > Vince >