Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: Notesfiles $Revision: 1.7.0.10 $; site ccvaxa Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxn!ihnp4!inuxc!pur-ee!uiucdcs!ccvaxa!srb From: srb@ccvaxa.UUCP Newsgroups: net.micro.mac Subject: Re: Mac hardware problem Message-ID: <2900009@ccvaxa> Date: Thu, 7-Nov-85 23:37:00 EST Article-I.D.: ccvaxa.2900009 Posted: Thu Nov 7 23:37:00 1985 Date-Received: Sun, 10-Nov-85 07:25:38 EST References: <3198@mhuxd.UUCP> Lines: 37 Nf-ID: #R:mhuxd.UUCP:-319800:ccvaxa:2900009:000:1570 Nf-From: ccvaxa.UUCP!srb Nov 7 22:37:00 1985 ------------ ------------ Someone who had done a DDJ conversion was asking about how to fix shorts under a socket without removing the whole row. One aid is to use a high-precision ohmmeter (Fluke 4 1/2 digit multifunction meter works), i.e., one which will discern a milliohm or so. You can locate a short to within an inch or so on 10 mil traces like the Mac's. We used to do it all the time on some boards we made. The easiest way to fix open/short problems under a socket is to use sockets with "open entry" pins. After being soldered into the board, the plastic shells of such sockets can simply be pulled off the pins (gently!) with a pair of pliers, leaving all 16 pins sitting firmly soldered into the board. Then put the shell back on (gently!) after the problem is fixed. You can generally spot such sockets by simply turning them over and looking at their undersides. (To be really sure, grab a pin with a pair of pliers and try to pull it out. It should come out and go back in relatively easily.) It is non-trivial to solder a replacement pin into the PC board straight enough to align correctly with the shell, without the shell in place. Don't try. Just put the pin into the shell, re-insert the shell/pin, and resolder. I did the Levco upgrade, and when finished with both the removal and the socket-soldering steps, spent a half hour with a 8x (slide loupe) magnifier examining holes, traces, etc. Time well spent. Found a couple of potential bridges. The upgraded Mac worked first time. Steve Bunch. ..!uiucdcs!ccvaxa!srb ------------