wire wrap machine

[Tony Duell]

> How about ECL? Moto used to advertise that the 10,000 series was 
> "wire-wrappable", but the WW samples I've seen have lots of twisted 
> pairs on them.  Looks like a real pain to do.

I've done that, it's not that bad...

You start by making the twisted pair wire (well, you can buy it, but it's 
expensive nad hard to get in small quantities). Put 2 spools of wire-wrap 
wire (differnt colours!) on a rod clamped in the vice, put the ends of 
the wire in the chuck of a hand drill, walk across the workshop and start 
cranking. You want about 3 twists paer inch for 100 ohm impedance (which 
is pretty standard).

Then strip the ends and wrap them. Run the pair across the PCB, cut off, 
strip, wrap. If possible use differential signals, if not, ground the 
other wire of the twisted pair.

I wrapped my own backplane for Unibus peripherals, and I actually 
believed what it said in the PDP11 buas handbook and used twiset pair for 
all the 'criticla' signals (MSYN, SSYN, SACK, etc). I then saw a real DEC 
backplane and found they didn't bother...

-tony