Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!pepper!cmcmanis From: cmcmanis%pepper@Sun.COM (Chuck McManis) Newsgroups: comp.sys.amiga Subject: Re: Cheap (inexpensive) hard drives Message-ID: <79342@sun.uucp> Date: 30 Nov 88 01:58:29 GMT References: <2570@m2-net.UUCP> <6080009@hpcupt1.HP.COM> Sender: news@sun.uucp Reply-To: cmcmanis@sun.UUCP (Chuck McManis) Organization: Sun Microsystems, Mountain View Lines: 78 In article <6080009@hpcupt1.HP.COM> (Paul Gootherts) writes: >> $20 2 Cables (Some handiwork required) > >Please elaborate. I need to get/make a cable to go from the back of an >ST-225N (50 pin ribbon) to either a 50 pin SCSI connector or a 25 pin >MAC connector. > >What kind of cable do you run from your drive to your controller? If >you built it from scratch, how did you find out what the pin connections >are? >- Paul Gootherts, Hewlett-Packard Co, hplabs!hpda!pdg Building a SCSI cable is fairly straight forward, yet it requires some manual dexterity and a good vice (smoking won't do :-)). The connector on the back of nearly every SCSI *device* known to man is a 50 pin parallel connector (2 rows of 25 pins) with a .1" pin spacing. The device will have a male plug the cable will require a female socket. An "insulation displacement" version of this connector will cost about $6 list at Active electronics or an equivalent. The "external" connector is specified by the SCSI standard to be a 50 pin "centronics type" connector. These are both a bit more expensive and a bit tougher to find. The local sales office of AMP sent me one as a sample, you may have to go through Hamilton-Avnet or an equivalent electronics distributor to get one. The single piece price of these varies, I was quoted $10. Since there is often a minimum purchase from a distributor you may end up buying more than one. (Arrow has a minimum purchase of $25, the salesperson offered to put one, two or three connectors in the box :-)) This connector will be a female I believe, since I don't have a Mac cable handy I'm guessing. The final piece of the mystery is some 50 conductor flat cable. This stuff is usually gray with a red stripe along one side of it. It will cost between $.50 and $1.50 a foot depending on your supplier, often, from a surplus store, you can buy a "scrap" cable that uses 50 conductor ribbon cable, cut the ends off and use the resulting length of cable in your new cable. If you use this method you should check for "missing" conductors or damage to the ribbon cable. Now you have your three pieces, two connectors and a section of ribbon cable. Carefully disassemble the 50 pin parallel connector and insert the cable between the "back" and the sharp "spines" on the connector. Note that the connector has an arrow or dot or the number 1 on the side where the red stripe should go. Let some of the cable pass through so that you have about 1/2" of cable on one side of the connector and the rest on the other side. Now place the whole deal into the vice so that closing the vice will squeeze the cable between the spines and the "back". MAKE SURE that the cable is perpindicular to the connector and that the spines all line up with conductors in the cable. Then, while keeping the various parts in place, clamp the vice down on the connector. It will "give" slightly when the spines displace the insulation, and the back of the connector will "snap" into a holding position. When there is no gap between the connector pieces and the cable give the vice an additional quarter turn and count to ten. This will insure the connection. Now remove the whole assembly and you will have something that from the side looks like this : XXX <- Connector back ------------------------XXX----- <- Excess Ribbon cable XXX <-- Connector front. XXX Using a pair of sharp scissors or an exacto knife cut off the excess cable, fold the remaining cable over the back and attach the strain relief. Do the exact same thing for the other connector on the other end. Now you can connect this cable to your disk drive or what ever inside the case and leave the 50 pin "centronics" type connector outside of the case. If you need to go from this connector to a 25 pin Mac type connector then by a Macintosh SCSI cable (off the shelf at about $19.95) if you need to go from this connector to another 50 pin centronics connector you can get a Macintosh SCSI "extension" cable off the shelf and use it. I don't reccomend you build your own 25 pin -> 50 pin cable. Good luck, --Chuck McManis uucp: {anywhere}!sun!cmcmanis BIX: cmcmanis ARPAnet: cmcmanis@sun.com These opinions are my own and no one elses, but you knew that didn't you.