"AUTO RADIO INFO."

IN THESE DAY'S OF RAPID CHANGING TECHNOLOGY/ THERE ARE VERY FEW OF US LEFT THAT ARE FAMILIAR WITH THE OLD AUTOMOBILE RADIO OF THE GOLDEN ERA OF RADIO. THE ANTIQUE RADIO'S WE KNOW TODAY, ARE THE RADIO'S I BEGAN SERVICING IN THE MID FORTIES SO I BRING TO THE TABLE SOME FIFTY YEARS OF EXPERIENCE.

  IT HAS BEEN SAID THAT THE BEST PLACE TO START IS THE BEGINNING,SO WE WILL BEGIN WITH THE EARLY RADIO'S OF THE 30'S & 40'S THESE RADIO'S WERE 6 VOLT D.C. (DIRECT CURRENT) THE HEART OF THESE RADIO'S WAS THE VIBRATOR, THE VIBRATOR MADE IT POSSIBLE TO HAVE CAR RADIO'S IN THOSE DAY'S, THE VACUUM TUBES USED THEN, REQUIRED A HIGH D.C. VOLTAGE TO OPERATE. THE VIBRATOR PRODUCED A HIGH A. C. (ALTERNATING CURRENT) ACROSS A POWER TRANSFORMER PRIMARY WINDING, WHICH TRANSFORMED INTO AN EVEN HIGHER A. C. VOLTAGE ACROSS THE SECONDARY WINDING, THIS VOLTAGE WAS THEN CHANGED TO A HIGH D.C. VOLTAGE BY MEA NS OF A RECTIFIER TUBE , AND THEN FILTERED TO A SMOOTH D.C. VOLTAGE BY ELECTROLYTIC CAPACITORS (CONDENSERS) AND THEN USED TO SUPPLY THE TUBES. IF THESE FILTER CAPACITORS DID NOT DO THEIR JOB IT WOULD CREATE A LOUD HUM IN THE SPEAKER EVEN WITH THE VOLUME TURNED ALL THE WAY DOWN. SO IF YOUR RADIO HAS A LOUD HUM FROM THE SPEAKER EVEN WITH THE VOLUME DOWN, YOU CAN BET THE FILTER CAPACITORS ARE DEFECTIVE.

  YOU HAVE TWO VOLTAGE SOURCES THAT SUPPLY THE TUBES, ONE IS THE HIGH D.C. VOLTAGE (250V TO 350V.) WE HAVE ALREADY TALKED ABOUT AND THE OTHER IS THE 6 VOLT BATTERY VOLTAGE THAT SUPPLY'S THE TUBE FILAMENTS TO LIGHT THEM UP, THIS 6 VOLTS ALSO SUPPLIES THE INITIAL VOLTAGE TO THE VIBRATOR. NOW WE HAVE ESTABLISHED THAT WE NEED THESE TWO VOLTAGES, HOW DO WE KNOW WHETHER WE HAVE THEM OR NOT? LET US TAKE THE 6 VOLT SUPPLY FIRST. IS THE SUPPLY THERE ? IS YOUR RADIO WIRED TO A LIVE 6 VOLT SOURCE? IS YOUR FUSE GOOD? IF THE SUPPLY TO YOUR RADIO IS THERE THE TUBE FILAMENTS SHOULD LIGHT UP. YOU WILL BE ABLE TO SEE THE FILAMENTS GLOW. IF THEY DO YOU HAVE ELIMINATED ONE POWER SOURCE FROM BEING THE TROUBLE.

LET US LOOK AT IT FROM ANOTHER ANGLE, SUPPOSE YOUR 6 VOLT SOURCE IS GOOD, THE FUSE IS GOOD, AND THE FILAMENTS OF THE TUBES DO NOT LIGHT UP, THEN YOU PROBABLY HAVE A BAD ON-OFF SWITCH OR A BROKEN 6 VOLT CONNECTION FROM THE SWITCH TO THE TUBE FILAMENTS. IS YOUR VIBRATOR WORKING? IS IT MAKING A VIBRATING SOUND? IF IT IS YOUR SWITCH IS O.K., YOU PROBABLY HAVE A BAD OR BROKEN CONNECTION TO THE FILAMENTS ONLY. IF THE FILAMENTS LIGHT UP AND THE VIBRATOR DOES NOT WORK THEN THE VIBRATOR IS PROBABLY DEFECTIVE. NOW IF THE VIBRATOR IS WORKING AND THE TUBES LIGHT UP, HOW DO WE FIND OUT WHETHER WE HAVE THE HIGH D.C. VOLTAGE SUPPLY (B+) TO THE TUBES? VERY SIMPLE { WITH OUT A VOLTMETER}. FIND THE TUBE LAYOUT CHART USUALLY ON THE INSIDE OF ONE OF THE RADIO CHASSIS COVERS LOCATE THE AUDIO OUTPUT TUBE, ON MOST 6VOLT RADIO'S THE OUTPUT TUBE IS A (6V6), )6K6)--(6F6) SOME OF THE EARLY MODELS USED A # 41-42 TUBE. ONCE YOU HAVE FOUND THE RIGHT TUBE WITH THE RADIO TURNED ON ( GIVE TUBES A FEW SECONDS TO LIGHT UP, SLOWLY PULL TUBE FROM ITS SOCKET, LISTEN FOR A POP FROM THE SPEAKER, IF YOU HEAR A POP FROM THE SPEAKER YOU HAVE DETERMINED SEVERAL THINGS, #1 THE HIGH D.C. SUPPLY VOLTAGE IS THERE,#2 THE SPEAKER IS GOOD, #3 THE OUTPUT TRANSFORMER IS GOOD AND #4 THE OUTPUT TUBE IS WORKING. ON THE OTHER HAND IF YOU DO NOT GET A POP FROM THE SPEAKER WHEN YOU PULL THE OUTPUT TUBE, THEN YOU HAVE SEVERAL POSSIBLE CAUSES. #1 THE SPEAKER COULD BE DEFECTIVE (OPENED VOICE COIL) CHECK OR SUBSTITUTE A KNOWN GOOD SPEAKER, #2 THE OUT PUT TRANSFORMER COULD BE DEFECTIVE ( POSSIBLE) BUT NOT LIKELY, THEY GAVE VERY LITTLE TROUBLE.#3 THE OUTPUT TUBE COULD BE DEFECTIVE, CHECK AND REPLACE. #4 THE HIGH D.C. VOLTAGE THAT SUPPLIES THE TUBES IS MISSING, THIS IS A TECHNICAL PROBLEM AND WOULD REQUIRE TEST EQUIPMENT.

HOWEVER, LET'S NOT GIVE UP YET. ONE POSSIBILITY REMAINS THAT IS WORTH CHECKING (THE RECTIFIER TUBE) THE TUBE THAT CONVERTS THE A. C. VOLTAGE FROM THE POWER TRANSFORMER TO D.C. VOLTAGE TO SUPPLY THE TUBES. THIS TUBE COULD BE DEFECTIVE. THE RECTIFIER TUBE IN MOST RADIO'S OF THIS ERA WAS #80_#84-#6Z4-#6X5-#OZ4. LET US SUPPOSE EVERYTHING WE HAVE CHECKED SO FAR IS O.K. THE TUBES LIGHT UP, THE VIBRATOR WORKS, WE GET A GOOD POP FROM THE SPEAKER, WHEN WE PULL THE OUTPUT TUBE, AND OUR RADIO STILL DOES NOT PLAY. LET US GO TO THE NEXT STAGE ON YOUR TUBE CHART, LOCATE THE AUDIO DETECTOR TUBE, EARLY RADIO'S (30'S & 40'S) POPULAR TUBES FOR THIS APPLICATION WERE # 75--#6Q7--#6J7----MID TO LATE 40'S #6SQ7. WHEN LOCATED PULL FROM SOCKET IN SAME MANNER AS YOU DID THE OUTPUT TUBE AND LISTEN FOR THE POP FROM SPEAKER  ( AT THIS POINT MAKE SURE THE VOLUME CONTROL IS TURNED ALL THE WAY TO THE LOUDEST POSITION). IF YOU HEAR THE POP IN THE SPEAKER GO TO THE NEXT TUBE. WORK YOUR WAY THROUGH THE REST OF THE TUBE COMPLIMENT. WHEN YOU COME TO A TUBE WHERE YOU DO NOT HEAR A POP IN THE SPEAKER, CHECK THAT TUBE OR REPLACE IT. IF YOU GO THROUGH ALL THE TUBES AND GET A POP FROM EACH ONE OF THEM ,, CHECK THE 1ST. R. F. TUBE, 6K7, 6SK7. 77. 78.CHECK OSCILLATOR TUBE, 6A7----6A8---6SA7, IF THEY CHECK O.K. CHECK THE ANTENNA, OBVIOUSLY, THIS WILL NOT FIND EVERY PROBLEM SOMETIMES THERE WILL BE A CIRCUIT PROBLEM WHICH REQUIRES TECHNICAL SKILLS, AND TEST EQUIPMENT. HOWEVER THIS TECHNIQUE WILL FIND MOST OF THEM------ KEEP VISITING MY WEB SITE, I WILL BE UPGRADING THIS REPORT FROM TIME TO TIME AND WILL GIVE DETAILS AND TECHNICAL INFORMATION ON CHECKING CIRCUITRY ON THESE OLD RADIO'S WITH A VOLT-OHM METER.

IN THE EARLY FIFTIES THE TUBE COMPLIMENT OF THEIR VIBRATOR POWERED RADIO CHANGED. MOST MODELS CHANGED TO A MINIATURE TUBE SERIES, { 6BA6, 6BE6, 6AV6, 6V6} THE SAME CHECKING PROCEDURES AS THE THIRTIES, AND FORTIES APPLY.


                                           A MAJOR CHANGE !

AUTOMOBILE MFG'S MADE A CHANGE IN THE MID 50'S. DO YOU KNOW WHAT IT WAS? 6 VOLT SYSTEMS WERE OUT, 12 VOLT SYSTEMS WERE IN. NOW VIBRATORS WERE 12 VOLT, TUBES WERE 12 VOLT, BUT THE METHOD FOR CHECKING I DESCRIBED FOR THE 30'S & 40'S, AND EARLY 50'S STILL APPLY. (SIMPLE SO FAR HUH?)

IN 1957 THINGS BECAME A LITTLE MORE COMPLICATED. GENERAL MOTORS, FORD, AND CHRYSLER CAME OUT WITH A HYBRID RADIO IN THEIR PUSHBUTTON MODELS IT USED AN AUDIO POWER TRANSISTOR FOR AUDIO OUTPUT, AND A NEW SERIES OF TUBES THAT WOULD OPERATE ON 12 VOLTS, THEY NO LONGER NEEDED THE HIGH (250V. TO 350V.) B+ TO SUPPLY TUBE ELEMENTS, UP UNTIL THIS TIME THE VIBRATOR POWERED RADIO'S COULD BE HAZARDOUS TO SERVICE , BECAUSE OF ELECTRICAL SHOCK. YOU HAD TO BE CAREFUL WHERE YOU PUT YOUR FINGERS WHILE SERVICING. BUT WITH THE NEW 12. VOLT (ONLY) HYBRID RADIO THIS HAZARD WAS MINIMIZED IF NOT TOTALLY ELIMINATED. SINCE THE POWER TRANSISTOR REQUIRED NO WARM UP TIME, YOU COULD TELL IF YOU HAD A POP FROM THE SPEAKER BY SIMPLY TURNING ON THE ON-OFF SWITCH. IF YOU HEAR A POP FROM SPEAKER WHEN YOU TURN THE SWITCH ON, THEN YOU KNOW THE 12VOLT SOURCE, THE SPEAKER, AND THE AUDIO OUTPUT TRANSISTOR IS WORKING. IF YOU DO NOT HEAR A POP, CHECK TO SEE IF THE TUBES ARE LIGHTING UP, IF THEY ARE, CHECK THE SPEAKER IF DEFECTIVE REPLACE. IF TUBES ARE NOT LIGHTING UP CHECK 12VOLT SUPPLY SOURCE. IF THE TUBES ARE LIGHTING UP THE SPEAKER CHECKS O.K. AND YOU STILL HAVE NO POP WHEN TURNING ON THE SWITCH THEN PROBABLY THE POWER TRANSISTOR IS DEFECTIVE. NOW IF YOU HAVE A GOOD POP FROM THE SPEAKER THE TUBES ARE LIGHTING UP AND THE RADIO STILL DOES NOT PLAY. USE THE SAME TECHNIQUE AS DESCRIBED PREVIOUSLY FOR EARLIER RADIO'S. PULL TUBES ONE AT A TIME AND LISTEN FOR POP IN SPEAKER. THESE HYBRID RADIO'S WERE AROUND THROUGH 1961. NOT ALL RADIO'S DURING THIS TIME WERE HYBRID MOST MANUAL MODELS (NO PUSHBUTTONS) STILL USED VIBRATOR POWER THROUGH 1958.

 

 

Most major automobile mfg's, from the fifties through the ninties used a negative battery ground.

1962 USHERED IN THE ALL TRANSISTOR RADIO, CHECKING AND SERVICING BECAME MORE DIFFICULT. THESE RADIO'S HAD PRINTED CIRCUIT BOARDS AND SOLDERED COMPONENTS. A FEW THINGS YOU COULD CHECK FROM A LAYMAN 'S PERSPECTIVE. FROM WHAT YOU COULD SEE AND WHAT YOU HEAR.. IS THERE A POP FROM THE SPEAKER WHEN YOU TURN THE RADIO ON? WHAT DOES THAT TELL YOU? IF THERE IS IT, TELLS YOU THAT YOU HAVE POWER TO THE RADIO, THE OUTPUT IS WORKING, AND THE SPEAKER IS WORKING. IF THE POP IS NOT THERE, EITHER LACK OF POWER SOURCE, FAULTY POWER TRANSISTOR, OR A DEFECTIVE SPEAKER. I WORKED ON THESE RADIO'S DURING THESE YEARS AND BELIEVE YOU ME WE HAD LOTS OF SPEAKER TROUBLE, THE SPEAKERS WERE MOUNTED ON TOP OF THE DASH, AND THE SUN CERTAINLY TOOK IT'S TOLL. SO THE SPEAKER SHOULD BE ONE OF THE FIRST THINGS TO CHECK..

IF YOU ARE A RESTORER OF OLD AUTOMOBILES, AND DO NOT HAVE A VOLT-OHM METER I WOULD SUGGEST YOU OBTAIN ONE, IF YOU HAVE A RESTORED AUTO, OR ARE IN THE PROCESS OF RESTORING ONE YOU WILL FIND MANY USES FOR ONE. NOT FOR JUST CHECKING THE RADIO, BUT FOR CHECKING THE REST OF THE CARS ELECTRICAL SYSTEMS. YOU CAN CHECK THE CONTINUITY OF THE ANTENNA, BY SETTING THE METER TO THE OHMS SCALE AND CHECKING FROM THE TIP OF THE ANTENNA LEAD WHERE IT PLUGS INTO THE RADIO TO THE ANTENNA MAST, OR FOR A SHORTED ANTENNA, BY CHECKING FROM THE ANTENNA TIP WHERE IT PLUGS INTO THE RADIO TO CHASSIS GROUND, ( YOU SHOULD HAVE NO READING ON METER) IF YOU DO YOUR ANTENNA IS SHORTED. ANOTHER USE IS TO USE THE METER ON THE LOW OHMS SCALE TO CHECK THE VOICE COIL OF THE SPEAKER. PLACE LEADS ON SPEAKER TERMINALS A READING ON THE METER INDICATES THAT THE SPEAKER VOICE COIL IS O.K.. ANOTHER USE IS TO CHECK 6VOLT & 12VOLT SOURCES, ON THE VOLTMETER , SELECT D.C. VOLTS ON THE FUNCTION SWITCH, AND SET THE RANGE SWITCH TO A RANGE JUST ABOVE 12VOLTS. THEN WITH THE GROUND LEAD OF THE METER (THE BLACK LEAD) ATTACHED TO THE CHASSIS (BODY) OF THE CAR OR RADIO CASE. TAKE THE POSITIVE LEAD OR (RED LEAD) AND CHECK VOLTAGES ANYWHERE IN THE RADIO OR ANY OTHER OF THE CARS ELECTRICAL CIRCUITS.

NOW LET ME ATTEMPT TO TEACH YOU TO BE A TECHNICIAN. WOULD' NT IT BE NICE TO BE ABLE TO CHECK D.C. CIRCUITS OF AN ALL TRANSISTOR CAR RADIO? TO BE ABLE TO KNOW IF EACH TRANSISTOR WAS CONDUCTING (WORKING) THE EARLY TRANSISTOR RADIO'S 1962 THROUGH THE LATE 60'S USED A GERMANIUM MATERIAL TO CONSTRUCT THE TRANSISTOR. MOST OF THE SIGNAL PATH TRANSISTORS WERE PNP (POSITIVE--NEGATIVE--POSITIVE) MATERIAL THESE TRANSLATED INTO THE ELEMENTS OF THE TRANSISTOR , THESE WERE THE EMITTER, BASE, AND COLLECTOR, THESE RADIO'S USED A CIRCUIT BOARD ALL PARTS ON ONE SIDE OF THE BOARD, ONLY PRINTED CIRCUIT ON THE OTHER. THE PRINTED CIRCUIT SIDE IS WHERE WE WILL DO OUR CHECKING. SINCE YOU CAN NOT SEE THE TRANSISTORS FROM THIS SIDE HOW DO WE KNOW WHERE THE CONNECTIONS FOR THE EMITTER, BASE AND COLLECTOR ARE LOCATED. SOME SETS YOU WOULD HAVE TO HAVE A SCHEMATIC DIAGRAM, AND CIRCUIT BOARD PICTURE TO SHOW LOCATION OF THESE POINTS, BUT LUCKILY MOST CUSTOM AUTO RADIO MFG'S (G. M. FORD, CHRYSLER, A. M. C. , MOTOROLA,  BENDIX  ETC. ) MARKED THESE POINTS ON THE CIRCUIT BOARD WITH "E" "B" "C". WITH THAT INFORMATION IN MIND WE CAN BEGIN OUR CHECKING. REMEMBERING, THAT ALL MAJOR MFG'S (ALL TRANSISTOR RADIO'S WERE 12 VOLTS, TAKE YOUR VOLT-OHM METER, SET TO D.C. VOLTS SET RANGE TO VOLTAGE JUST ABOVE 12 VOLTS. NOW WE WILL BEGIN OUR CHECK.

FIRST FIND THE 12 VOLT SOURCE ON THE PRINTED CIRCUIT BOARD. TO FIND THIS SOURCE, TAKE THE NEGATIVE (BLACK LEAD) OF THE METER CLIP IT TO THE RADIO CHASSIS (CASE). TAKE THE RED OR POSITIVE LEAD OF THE METER FIND A PLACE ON THE CIRCUIT BOARD WHERE METER READS AROUND 11 TO 12 VOLTS. THE BEST PLACE TO FIND THIS IS WHERE THE FILTER CAPACITOR COMES THROUGH THE CIRCUIT BOARD, ONE OF THESE CONNECTIONS WILL BE 11 TO 12 VOLTS. HOLD THE RED (POSITIVE) LEAD ON THIS CONNECTION, TAKE THE BLACK (NEGATIVE) LEAD AND PLACE IT ON ONE OF THE POINTS MARKED "E" IT DOES NOT MATTER WHICH ONE YOU START WITH, WE ARE GOING TO CHECK EACH ONE TO SEE IF IT IS CONDUCTING. WHAT WE ARE DOING IS MEASURING THE VOLTAGE DROP ACROSS THE EMITTER RESISTOR. IF YOU MEASURE A READING OR A DROP ACROSS THE RESISTOR THE STAGE IS CONDUCTING IF NO READING AT ALL THEN THE STAGE IS NOT CONDUCTING. WITH RED LEAD ON 12VOLT SOURCE. TAKE BLACK LEAD AND CHECK ALL POINTS MARKED "E" WHEN YOU FIND ONE WHERE THERE IS NO READING . THAT MEANS THE STAGE IS NOT CONDUCTING, REPLACE THAT TRANSISTOR. NOW THERE ARE MANY OTHER THINGS INVOLVED IN THE CONDUCTION OF A STAGE, WHAT I HAVE DONE IS GIVE YOU A WAY TO ISOLATE A STAGE, AND IN MOST CASES A NEW TRANSISTOR WILL CURE YOUR PROBLEM.

NOT ALL TRANSISTOR CONDUCTION PROBLEMS ARE AS SIMPLE AS THE TRANSISTOR NOT CONDUCTING SOMETIMES THEY WILL CONDUCT BUT NOT PROPERLY. SOME TIMES THEY WILL CONDUCT TOO HIGH, SOMETIMES TOO LOW. ALL HAVING TO DO WITH THE BIAS OF THE TRANSISTOR. THE GERMANIUM TRANSISTOR OF THE 60'S SHOULD HAVE A BIAS( BIAS BEING THE VOLTAGE DIFFERENCE BETWEEN THE EMITTER AND THE BASE CONNECTIONS OF THE TRANSISTOR YOU CAN CHECK THIS BIAS BY MEASURING WITH YOUR VOLT METER ON A LOW VOLTAGE SCALE, ACROSS THE EMITTER &BASE TERMINALS ON THE CIRCUIT BOARD . THE BIAS REQUIRED FOR THESE TRANSISTORS TO CONDUCT WAS .2 (TWO TENTHS) OF A VOLT. IF THE READING IS VERY CLOSE TO THIS YOUR BIAS IS O.K. NOW THERE IS A RULE OF THUMB HERE IF THE BIAS IS NORMAL AND THE TRANSISTOR IS NOT CONDUCTING( SEE PREVIOUS PARAGRAPH) THEN THE TRANSISTOR IS BAD. IF THE BIAS IS HIGH OVER TWO TENTHS OF A VOLT, AND THE CONDUCTION IS HIGH THEN THE TRANSISTOR IS DOING WHAT IT IS TOLD TO DO, THE TROUBLE IS ANOTHER COMPONENT IN THE CIRCUIT. LIKE WISE IF THE BIAS IS LOW AND THE CONDUCTION IS LOW THE TRANSISTOR IS DOING WHAT IT .IS TOLD TO DO AND IS O.K. SOME OTHER COMPONENT IS AT FAULT.

WELCOME TO THE 70'S

THE 70'S BROUGHT IN THE SILICON TRANSISTOR MADE FROM A SILICON MATERIAL. REQUIRING A DIFFERENT APPROACH. THE SIGNAL PATH TRANSISTORS IN MOST RADIO'S WERE N. P. N. (NEGATIVE--POSITIVE--NEGATIVE) CHECKING CONDUCTION SINCE THE EMITTER IS NOW NEGATIVE, WITH RESPECT TO THE COLLECTOR, IS NOW DIFFERENT. ON THESE RADIOS SOME TIMES THE EMITTER OF THE TRANSISTOR IS GROUNDED. SO TO CHECK CONDUCTION WE WILL MEASURE THE  VOLTAGE  DROP ACROSS THE COLLECTOR LOAD RESISTOR. TO DO THIS SET YOUR METER TO D. C. VOLTS, RANGE TO LOW 1. 5 VOLT TO 3 VOLT SCALE. FIND YOUR 12VOLT D.C. SOURCE VOLTAGE PLACE YOUR RED POSITIVE LEAD ON THIS POINT TAKE THE BLACK NEGATIVE LEAD AND CHECK FROM ALL TRANSISTOR COLLECTOR "C" CONNECTIONS A READING INDICATES THAT YOU HAVE A DROP ACROSS THE COLLECTOR LOAD RESISTOR INDICATING THAT THE TRANSISTOR IS CONDUCTING. MAKE THIS CHECK ON ALL TRANSISTOR COLLECTORS WHEN YOU FIND ONE THAT DOES NOT HAVE A READING, THAT STAGE IS DEAD, CHANCES ARE THE TRANSISTOR IS DEFECTIVE. BY THE WAY THE BIAS IS DIFFERENT ON THE SILICON TRANSISTORS ALSO. INSTEAD OF BEING TWO TENTHS OF A VOLT LIKE THE GERMANIUM TRANSISTORS. OF THE PAST. THE BIAS OR (DIFFERENCE BETWEEN EMITTER AND BASE VOLTAGE) ON THE SILICON IS SIX TENTHS (. 6VOLT) BIAS AND CONDUCTION CHECKS SHOULD REFLECT THIS DIFFERENCE.

IN 1978 WE BEGAN TO SEE DIGITAL DISPLAY RADIO'S. THEY DISPLAYED FREQUENCY AND CLOCK AND THE CIRCUITRY FOR THESE WAS MOSTLY INTEGRATED CIRCUIT ( CHIPS) VERY LITTLE A LAYMAN COULD DO WITH THESE RADIO'S. YOU COULD CHECK SPEAKERS, ANTENNA AND BY WHAT YOU SAW OR DID NOT SEE WHAT YOU COULD HEAR OR COULD NOT HEAD YOU MIGHT PIN IT DOWN TO A SECTION OR A CERTAIN CHIP. BUT THERE AGAIN WITHOUT SOME EXPERIENCE AND EQUIPMENT EVEN IF YOU LOCATED A DEFECTIVE CHIP, IT WOULD BE VERY DIFFICULT TO REPLACE WITHOUT THE RIGHT EQUIPMENT. A LITTLE LATER IN THE 80'S THE DESIGNERS WENT TO A MICROPROCESSOR CHIP, WHICH RECEIVED INFORMATION FROM THE A.M. --F. M. RECEIVER SECTION OF THE RADIO, PROCESSED IT AND SENT IT TO THE DIGITAL DISPLAY MODULE. WHICH TRANSLATED INTO A VISUAL DISPLAY OF THE INFORMATION, EITHER FREQUENCY OR TIME. BY THE WAY THE RECEIVER SECTIONS OF THESE RADIO'S ARE CHECKED THE SAME WAY AS THE 70'S SETS WE DISCUSSED IN EARLIER PARAGRAPHS. THE DATA INFORMATION TO THE MICROPROCESSOR WAS PROVIDED BY MODE, AND FUNCTION SWITCHES OR CONTROLS. FOR EXAMPLE ( VOLUME, TUNING, PUSHBUTTON, SEEK, SCAN AND TIME SET. SERVICE ON THE PROCESSOR SECTION OF THESE RADIOS IS VERY DETAILED AND REQUIRE SOME KNOWLEDGE OF THE THEORY BEHIND THEM.

AM--FM RADIO'S

THE AM--FM RADIO CAN BE DIVIDED INTO THREE SECTIONS ( A.M.) CONSISTS OF A.M. RECEIVER INCLUDING R. F. OSCILLATOR, AND I.F ( INTERMEDIATE FREQUENCY) SECTIONS. THE (F. M.) CONSISTS OF F. M. RECEIVER INCLUDING F. M. R. F. (RADIO FREQ.), FM OSCILLATOR, AND FM I. F. SECTIONS. ( AUDIO) THE AUDIO SECTION IS COMMON TO BOTH AM & FM IN OTHER WORDS THE A.M. AND THE F. M. SECTIONS USE THE SAME AUDIO, SWITCHING IS ACCOMPLISHED BY THE AM--FM. SWITCH. NARROWING THE SEARCH TO A SECTION CAN BE RELATIVELY EASY. IF EITHER THE A.M. OR F. M. PLAY THEN YOU KNOW THE AUDIO SECTION IS GOOD. IF NEITHER PLAY THE 12.VOLT SOURCE IS MISSING OR THE AUDIO SECTION IS DEFECTIVE. IF A.M. PLAYS BUT F. M. DOES NOT TROUBLE IS IN THE F. M. SECTION, IF F. M. PLAYS AND A.M. DOES NOT, THE FIRST PLACE TO CHECK IS THE ANTENNA. ( F. M. WILL PLAY ON STRONGER LOCAL STATIONS WITH A DEFECTIVE ANTENNA ( SHORTED OR OPEN CONNECTION). SO IF THE A.M. IS DEAD AND THE F. M. PLAYS ON LOCAL STATIONS, CHANGE THE ANTENNA, IF A.M. PLAYS AND THE F. M. DOES NOT, TROUBLE THEN HAS TO BE IN THE F. M. SECTION CHECK F. M. SECTION AS PER PREVIOUS INSTRUCTIONS FOR ALL TRANSISTOR RADIO'S.

WONDER BAR RADIO'S

WONDER BAR RADIO'S ARE CHECKED THE SAME WAY AS ALL THE CHECKING PROCEDURES WE HAVE MENTIONED, ACCORDING TO THE YEAR AND MODEL. ANY OTHER PROBLEM WOULD BE MECHANICAL.

I HAVE REALLY ENJOYED WRITING AND SHARING THIS INFORMATION I AM EXCITED ABOUT THE FACT THAT I CAN HELP YOU WITH INFORMATION THAT WILL ANSWER SOME OF YOUR QUESTIONS, AND ASSIST YOU IN SOLVING SOME OF YOUR RADIO TROUBLES. KEEP CHECKING MY WEB SITE FOR UPDATE INFORMATION. FEEL FREE TO PRINT AND SAVE ALL INFORMATION FOR FURTHER  REFERENCE. IF YOU HAVE ANY QUESTIONS ABOUT DIFFICULT SERVICE RELATED PROBLEMS, PLEASE CONTACT ME @  dcosby1@cox.net

INFORMATION, ON CHECKING FOR SHORTS ON VIBRATOR POWERED

If you have a radio that blows fuses regularly you have a overload or direct short, there is a difference a direct short will blow the fuse immediately. where an overload short will blow the fuse after a few seconds or several seconds depending on the current draw. a direct short can be an pinched wire some where in the power lead or internally in the radio or most probably stuck points on the vibrator. one way to find out which is unplug the vibrator if the short clears the vibrator is at fault. however if the short is still there look for shorted wires from the source to the base of the vibrator. Now! if you have an excessive current short, one that takes a few seconds to blow the fuse, you can tell the vibrator is working with this type of short until the fuse blows. If this is the case, check for a shorted buffer condenser across pins 3&5 of the rectifier tube. cut one lead loose and see if the short disappears, if it does replace the buffer condenser. If not the vibrator or power transformer is probably shorted and will have to be replaced. now sometimes the short is in the B+ circuit but to create a short that would blow the fuse the rectifier tube or the first filter capacitor would have to be shorted, but a shorted first B+ filter would destroy th rectifier tube before blowing the fuse. so if the radio is still shorted after you change the vibrator, buffer condenser and rectifier tube the problem is usually the vibrator transformer. the rectifier tube on most of the old sets were the following, OZ4,6X5,80/84 GOOD LUCK !

Some of you have shown an interest in 6volt to 12volt conversion. In radio's prior to 1955 for general motors cars and 1956 for ford the radios were 6volt. many restorers are changing the 6volt system to 12volts. for the convenience of replacement parts and less current drain for accessories and general compatibility with today's system. My information will be directed toward the radio. first replace the 6volt tubes with 12 volt tubes of the same type and number.

replace the 6volt vibrator with a 12volt vibrator, you can obtain these through "antique electronic supply" in Tempe AZ. just specify whether your car is (negative or positive ground) be sure you do this because they will not interchange. replace the dial light to 12volt, most times you can get by with the 6volt vibrator transformer, but sometimes it has to be changed also. another remedy could be a 12volt to 6volt dropping resistor assembly. this is a good remedy if you can find a resistor block that dissipates the heat and is mounted far enough away from any material in the car that would cause a fire hazard