MY PURPOSE FOR THIS PARTICULAR FILE IS TO INSTRUCT THE LAYMAN IN THE PROPER INSTALLATION PROCEDURE FOR THE CONNEX (EB-3) ECHO BOARD. THE INSTRUCTIONS GIVEN HERE WILL NOT BE CHASSIS SPECIFIC, AS THE ASSUMP- TION ON MY PART IS THAT ANYONE ATTEMPTING TO FOLLOW ALONG WILL HAVE THE NECESSARY ELECTRONICS BACKGROUND REQUIRED TO DO SO. I FEEL THAT THE INFORMATION CONTAINED HEREIN IS ALSO NECESSARY DUE TO THE FACT THAT THE INSTRUCTIONS SUPPLIED WITH THE BOARD ARE INACCURATE, AS WELL AS INCOMPLETE. BEFORE WE GET STARTED, HERE ARE A FEW OF MY OWN COM- MENTS AND INSIGHTS. AFTER MANY YEARS OF REMOVING AND REINSTALLING CONNEX BOARDS IN A WIDE VARIETY OF RADIOS, I HAVE COME UP WITH A LIST OF THE MOST COMMONLY FOUND OR "CREATED" PROBLEMS RESULTING FROM THE IMPROPER INSTALLATION OF THIS EVER POPULAR AFTERMARKET DEVICE, AND HERE THEY ARE.....!!!!! #1....THE MANUFACTURERS OF THE CONNEX BOARD (IN THEIR INFINITE WISDOM) PROVIDED A PAIR OF MOUNTING BRACKETS WITH WHICH TO "MOUNT" THE BOARD TO THE FRAME OF THE RADIO. AND DID YOU KNOW THAT MOST OF THE RADIOS ALREADY HAVE HOLES DRILLED TO ACCOMODATE THE BOARD, RATHER NICELY AS A MATTER OF FACT.! THE BOARD NEEDS TO BE MOUNTED USING AT LEAST ONE OF THESE BRACKETS TO FACILITATE PROPER GROUNDING AS WELL AS THE RF STABILITY OF THE BOARD. YOU SO-CALLED TECHNICIANS OUT THERE WHO WRAP THESE BOARDS UP IN TOILET PAPER, NAPKINS, PLASTIC BAGS AND THE LIKE AND THEN TOP IT OFF WITH HALF A ROLL OF ELECTRICAL TAPE ARE KNOWINGLY OR OTHERWISE DOING YOURSELVES AND YOUR CUSTOMERS A GREAT DISSERVICE, AND AT THE SAME TIME PROVIDING QUITE A BIT OF WORK FOR OTHER SHOPS AROUND THE COUNTRY, BECAUSE, AS THEY INVARIABLY DO, THESE THINGS SOONER OR LATER COME INTO A SHOP WHERE THE CUSTOMER COMPLAINS, THE RADIO IS BENCHED, AND 100 TIMES OUT OF 100 THE SOURCE OF HIS COM- PLAINT CAN BE DIRECTLY TRACED TO THE CONNEX BOARD. MOUNT THE BOARD, TAKE YOUR TIME, AND DO IT RIGHT. IF YOU DON'T, WE WILL! #2....I'M SURE THAT ALL OF YOU, AT ONE TIME OR ANOTHER, HAVE RUN INTO ONE OF THESE BOARDS IN A RADIO IN A SITUATION WHERE WHEN THE MIC. GAIN IS FULL ON, THE RADIO TRANSMITS A TYPE OF SQUEAL, BUT HAS ABSOLUTELY NOTHING TO DO WITH THE TALKBACK CIRCUIT. THERE ARE TWO AREAS THAT NEED TO BE INSPECTED. FIRST OF ALL, CHECK TO SEE WHETHER THE OR NOT THE POWER GROUND CONNECTION IS BEING USED. (THE BLACK WIRE RIGHT NEXT TO THE BROWN 8 VOLT DC LEAD. DO NOT CONNECT THIS LEAD TO ANYTHING IN ANY RADIO AT ANY TIME WHATSOEVER.! CUT IT OFF FLUSH AT THE PLUG AND FORGET ABOUT IT!!!) WHEN THIS LEAD IS CONNECTED SIMULTANEOUSLY WITH BOTH THE SHIELD GROUND RETURNS ON THE AUDIO INPUT AND OUTPUT LEADS TO THE BOARD, YOU ARE CREATING A "GROUND LOOP". GROUND LOOPS CAUSE RF FEEDBACK IN THE BOARD AS WELL AS DESTABILIZING THE BUCKET CIRCUITRY, CAUSING OSCILLATION, AS WELL AS A HOST OF OTHER PROBLEMS. THE OTHER AREA THAT NEEDS TO BE DISCUSSED IS THE FACT THAT THIS BOARD IS DESIGN- TO FUNCTION PROPERLY AT 8 VOLTS, + OR -. WE SEE SO MANY RADIOS COME INTO THE SHOP WIRED DIRECTLY TO THE 13.8 VOLT RAIL. FORGET ABOUT THE SERIES DROPPING RESISTORS. I HAVE YET TO FIND A RADIO THAT DOESN'T HAVE A STABLE 8 VOLT SOURCE FROM WHICH TO POWER THE CONNEX BOARD. TAKE YOUR VOLTOHM METER, GROUND THE NEGATIVE LEAD, AND IN TRANSMIT MODE, FIND AN 8 VOLT SOURCE ON THE CHASSIS OF THE RADIO. IT'S THERE, JUST LOOK FOR IT AND FIND IT. WHEN YOU DO, CONNECT THE BROWN WIRE FROM THE CONNEX BOARD TO THAT POINT. SIMPLE! #3....WHEN YOU ARE LOOKING FOR A PLACE TO GROUND THE INPUT AND OUTPUT SHIELDS, (YES, THEY DO NEED TO BE GROUNDED) TWIST THEM TOGETHER AND TIN WITH SOLDER, THEN GROUND THEM AT ONLY ONE OF TWO POINTS. EITHER AN IF RECEIVER CAN IN THE VICINITY OF THE MIC. CONNECTOR OR DIRECTLY TO THE GROUND PIN OF THE MIC CONNECTOR!! YOU WILL FIND THAT IN THE "NEW" COBRAS COMING FROM CHINA, GROUNDING TO AN IF RECEIVER CAN WILL NOT WORK. THE GROUND FOIL ETCH ON THE CIRCUIT BOARDS IN THESE RADIOS IS SO THIN AND INDUCTIVE THAT GROUNDING HERE "WILL NOT WORK". BUT, GROUNDING AT THE MIC CONNECTOR GROUND PIN IS VIRTUALLY FOOLPROOF!!!! #4....ALWAYS BREAK OPEN THE LINE FROM THE MIC. GAIN CONTROL TO THE MIC. CHASSIS CONNECTOR AND WIRE INPUT AND OUTPUT AT THIS POINT ONLY! YOU SAY YOU CAN'T TELL WHICH ONE THAT IS? GRAB THAT VOLTOHM METER AGAIN, SET ON RESISTANCE OR CONTINUITY, TOUCH ONE LEAD TO THE MIC. AUDIO PIN, THEN WITH THE FREE LEAD, PROBE THE THREE PADS OF THE MIC, GAIN CONTROL. THE ONE THAT INDICATES THE LEAST OR NO RESISTANCE IS THE LEAD TO BREAK OUT FOR CONNECTING THE SHIELDED INPUT AND OUTPUT LINES OF THE CONNEX BOARD. AND WHEN YOU CONNECT THE WIRES, FORGET ABOUT THE "ELECTRICAL TAPE" AND USE THE PROPER SIZE HEAT SHRINK TU- BING, IT'S SO MUCH MORE PROFESSIONAL LOOKING, AND IF THE CUSTOMER IS WATCHING, I CAN TELL YOU THAT HE THINKS SO TOO!...................... #5....NOW THIS IS THE ICING ON THE CAKE. TECHNICIANS UNFAMILIAR WITH THE CONNEX BOARD WILL MISS THIS ONE EVERY TIME. LOCATE THE INPUT LINE TO THE CONNEX BOARD. YOU WILL NOTICE A 1K OHM RESISTOR CONNECTED FROM THE CENTER CONDUCTOR OF THE INPUT CABLE TO GROUND, OR THE SHIELD. UNSOLDER THIS RESISTOR FROM THE BOARD, OR SIMPLY CUT IT OPEN. YOU HAVE JUST INCREASED THE INPUT LEVEL FROM THE MICROPHONE TO THE INPUT OF THE CONNEX BOARD BY 3DB. THIS MODIFICATION IS NECESSARY WHEN THE RADIO IS USED WITH MICROPHONES SUCH AS THE RK-56/B OR THE ASTATIC 636L. #6....BEFORE YOU INSTALL THE CONTROL KNOBSET, (YES, YOU WILL FINALLY GET A CHANCE TO USE THAT ROLL OF ELECTRICAL TAPE AFTER ALL) WRAP ENOUGH TAPE AROUND THE FRONT OF THE CONTROL TO COVER THE THREE TAP CONTACTS ON THE FRONT OF THE BAKELITE BOARD TO PROTECT THEM FROM SHORTING TO THE FRAME. NOT TOO TIGHT, EITHER, AS THE TERMINALS CON- NECTING THE WIRE HARNESS COULD SHORT AS WELL. DON'T FORGET TO READ THE FILE TITLED "TALKBK.TXT" FOR TIPS ON INSTAL- LING TALKBACK, AND REMEMBER, IF THE TALKBACK IS SO LOUD THAT YOU CAN'T RUN THE MIC. GAIN WIDE OPEN, ..YOU'RE..NOT..GETTING..OUT!!!!!!!