=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- DISCLAIMER DISCLAIMER DISCLAIMER DISCLAIMER DISCLAIMER DISCLAIMER The following document is _not_ an instruction manual, it is a discription of a modification I made to my own computer. Since I have no guarantee as to what experience the reader of this article may have, or the equipment said person may have, I can not be liable for any damage caused as a result of reading this article and applying the information therin. -William Mills. =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- (c) Copyright 1989 by William Mills This article may be freely reproduced and distributed, as long as it is distributed in it's intirety, with disclaimer included. ADDING AUDIO PORTS TO AN ATARI ST WHY ADD AUDIO PORTS? I like a little more thunder to the sound my ST produces. Audio ports allow the ST to be connected to a stereo, or other sound amplifying/recording device. This allows digitally edited sounds to be recorded to audio tape, or as sound tracks to video tape. It also allows the use of headsets, or stereo speakers for video games. (headsets give 'FALCON' a real'in the cocpit' feeling, while stereo speakers provide an afterburner that you can *feel*). Although the ST only has a monaural audio output, I decided to use 2 audio jacks, because it would mean less clutter on my desk (no RCA 'Y' splitter behind the ST). NECESSARY PARTS AND TOOLS: * Philips screwdriver * Needle nose pliers * 2 RCA female panel mount plugs (a couple of dollars from an electroncs store ) * a couple of feet of insulated wire (I stipped out a couple of wires from a ribbon cable, it's just the right weight) * a soldering pencil * a drill (hand or electric, I used a pocket knife) * a small ammount of resin core solder * a conductive anti-static mat with grounding wrist strap * a pair of cutters or tin snips The hardest thing (I would assume) to come up with is the mat. They are fairly expensive (I think about $30 for a portable one). This is not something to skimp on, ESD (electrostatic discharge) can do some serious damage. Any discharge that can be felt is at least 6000 ( or is that 3000, I don't remember for sure, still, it's quite high) volts. A discharge of as little as 60 volts can blow modern electronic circuits. Simply raising your arm while wearing a jacket can develop a charge of 2,000+ volts. (these figures are from 'The Dangers of ESD' Apple service training video) Fortunately, there is a low cost alternative that should do nearly as good of a job. (I've used it with no damage to several machines that I have worked on at home) Take a cover your work surface with a damp towel (not *soaking*, just damp). Take some light, flexible wire, strip it's insulation, and loop it around your wrist, so that it connects your wrist to the towel, thus balancing the charge between the towel and yourself. Run another similar wire from the towel to the screw that holds the panel on an electric socket. This will drain excess charges to the ground (do *not* not put the wire into the socket, I don't want to get sued because someone read this and plugged themself into 120volts! Also, *never* repair a monitor while grounded, it makes it that much easier for the CRT to discharge and *KILL* you!) The first step is to decide where to put the plugs on the case. I installed mine to the left of the monitor cable, above the RF modulator. I have on older 520 ST (w/1meg ram). On newer STs which lack the RF modulator, there should be plenty of room to the left of the monitor plug (assumming the modulator space was left vacant, as it was on 1987 1040 STs) Next, it's time to disassemble the machine. Start by wearing your wrist strap, and making sure the mat is grounded. Set the ST (with nothing plugged into it) face down on the mat. Next remove all of the screws from the bottom of the case. Now, while holding it all together, flip the ST over, and remove the top cover. The keyboard can now be easilly lifted away. You will find that it is connected to the motherboard by about 20 wires that lead to a connector. Carefully slide the connector off of the motherboard (don't bend the pins). The next step is to remove the radio shield. Take out the screws which hold it to the motherboard, and then use the needle nose pliers to sraighten the tabs that hold the shield down. The shield will then lift away. Now is the time to cut the case. drill or cut the appropriate sized holes, and mount the RCA jack(s). Make sure that they are not in a position where they will touch other components, and that they will still allow the cover to fit. Now comes the soldering, if you hav ANY electrical soldering experience, this will be a snap. If not, find somemone who does to give you some pointers. I won't go basic soldering and wire stipping instuctions here, because I'm assuming that anyone who is willing to do a hardware hack on their ST, probably can hold their own with a soldering iron. If you are putting two jacks into your ST, you must solder a short wire between the outside leads of each jack. Another short wire should connect the inside leads of the jacks. Since connecting the jacks to the motherboard will mean that it is (somewhat) permanently wired to the case, you may want these wires about a foot long each. Solder one long wire from the outside lead of one of the RCA jacks to a ground on the motherboard. Since the signal ground on the monitor plug is hard to reach from the top of the board, I simply soldered mine to the metal case on the serial port. This seems to be abouth the easiest plece to put it, and I highly recommend it. The another wire must be soldered onto the inside lead of one of the jacks. The other end of this wire needs to go to the audio line on the monitor plug (pin 1). Pin one is on the top left (when facing the plug from theback), and it's lead (at least on my ST, they may have changed brands of plugs since 1986) is on the top right when facing from the front of the machine, and has plento of room for the wire to be soldered onto it. That's all there is to it, just put the ST back together opposite the way you took it apart, (make sure the keyboard cable is facing the right direction, and don't force it) and you'll be set. The entire mod can probably be done in less time than it takes to read this article. Just slap a 2 line stereo patch cord on the ST, and hook it to the external input jacks on a stereo, and you're all set. I have recently been told that pin 2 on the monitor plug (the next one over from pin 1) carries an NTSC composite video signal. I haven't had time to check this out yet, but if it is true, the above procedure will yeild a video port which can be connected to a VCR (to record, or display on a TV) or a composite monitor (I don't know why you would want to). BTW, Atari lists pin 2 as 'reserved'. Well, I hope this is of help to someone, I didn't expect it to be so long winded when I started. Be seeing you... (too bad alt.tv.prisoner got canned) -Bill Mills bill@csufres.csufresno.edu billm@gaudi.csufresno.edu Snail Mail: 299 W. Birch Ave, Hanford, CA 93230 BTW, if you are a paintball player, drop me some e-mail. I am captain of 'BOB's Biz Boys. Check out our keen logo in the Spring 1990 team listing issue of PAINTBALL magasine.