Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site bmcg.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!bellcore!decvax!ittvax!dcdwest!sdcsvax!bmcg!yrdbrd From: yrdbrd@bmcg.UUCP (Larry J. Huntley) Newsgroups: net.arch,net.micro Subject: Re: How to fab One-Of-A-Kind systems? Message-ID: <1684@bmcg.UUCP> Date: Fri, 17-May-85 20:24:24 EDT Article-I.D.: bmcg.1684 Posted: Fri May 17 20:24:24 1985 Date-Received: Thu, 23-May-85 01:06:55 EDT References: <10526@brl-tgr.ARPA> <612@houxu.UUCP> Reply-To: yrdbrd@bmcg.UUCP (Larry J. Huntley) Organization: Burroughs Corp. ASG, San Diego, CA. Lines: 81 Xref: watmath net.arch:1231 net.micro:10456 Summary: In article <612@houxu.UUCP> rbc@houxu.UUCP (R.CONNAGHAN) writes: >No one has mentioned Multiwire. >Generally very fast turn-around compared to Printed Circuits. > >The favorite has gone from wire-wrap to Multiwire. > >A comment on wire-wrap robustness. >(etc.) > >Robert Connaghan >Microprocessor Group >AT&T Bell Labs - Holmdel, N.J. >houxu!rbc Although I can agree with Robert about Multiwire, I think that it is a little out of sync for the application the original poster had in mind (hobbyist or university lab "one-off" system, I think.) Multi- wire is great for something that you need 25 -- 1000 of. Computervision used the technique to build add-on boards in Data General computers, and they were at least as reliable as the multi-layer PCBs that were in the computers. It's a bit expensive for a single board, though. I have been using wire-wrap for 13 years now, and have never had any problems with well-planned, well-wrapped boards/systems. Some further comments: (1) The problems encountered with wire-wrap usually involve (1) the insulation failing where a wire passes around the corner of a socket/pin and cuts through the insulation, causing a short, or (2) a wire under so much tension that the inner conductor breaks (usually at the point where the wrap starts around the post) but the insulation stays intact, making the problem virtually impossible to find visually. (2) There are wire-wrap bits and sleeves which cut and strip the insulation as the wrap is being made. One of these pays for itself with the first board you build with more than 25 wires. (NO, this is NOT the "slit & wrap" tool discussed earlier. This is a genuine wire-wrap tool and it makes a proper 'modified' wrap on standard 0.025" sq. pins. If you need more information, let me know. I'll look it up.) (3) Be sure to use "levels" on your pins, and plan your physical layout to minimize wire lengths. Leveling the wires looks like this: Wiring Side | | | | | | <- pins |--------| |--------| |-------| <-- level 2 | | | | | | | |-----------| |---------| | <-- level 1 | | | | | | ------------------------------------------------------ <- board ------------------------------------------------------ | | | | | | | | | | | | <- sockets ------------ ------------ ----------- Component Side (4) Beware of stray inductance in wire-wrapped boards. If possible make your connections to power and ground with 20 ga. solid wire, soldered to busses on the board. If you must wrap the power leads, keep the wires as short as possible. A loop of 1" of 30 AWG wire can exhibit enough inductance to induce voltage spikes as high as 1 volt on the power leads of devices which are switching at 4 MHz. Wire-wrapping dynamic RAM arrays can be particularly exciting. Have great fun, 'brd -- Larry J. Huntley Burroughs -(B)- Corporation Advanced Systems Group MS-703 10850 Via Frontera San Diego, CA 92128 (619) 485-4544 -*- Non Circum Copulae -*-