Technique George NI Myers Receiver Repairs HAVE DECIDED am primarily flier Building airplanes repairing models radios something out necessity Therefore have fix radio try simple ways first workbench has oscilloscope vacu um-tube voltmeter assorted signal genera tors other gadgets like special probes above Probably yours doesnt therefore would useless describe techniques require follow ing discussion will emphasize procedures require tools normally found model-builders shop dont have multi-tester Volt-Ohm Meter please get $20 should enough buy good local electronics supply house mail-order shop important thing look DC Voltage scales about 15 6 12 volts full scale sensi tivity 20000 ohms/volt should also have resistance ohms scale shows about 50 ohms center arc has multipliers selec tor switch Xl X 10 X 100 X 1000 XlK Lets begin assuming radio system inoperative did get way radio working fine until crash know enough begin looking crash-type damage check broken crystal broken wires missing antenna other things nature other hand everything working fine last month now wont play begin checking battery packs open shorted cells checking charger make sure its doing its job looking dirt corrosion prevents switch plugs making con tact Whatever do systematically keep records try head can sure will waste time Suppose cant find anything obviously wrong system smart thing to eliminate possibili ties time transmitter putting out signal several ways find out could switch listen scream Im hit dont think flying buddies would appreciate test technique Get frequency pin clothespin same colors flag antenna find somebody set same frequency yours Ask him turn receiver turn transmitter See can make servos move controlled man ner Check ground range should about same used have receiver transmitter fine control functions may show up different places example aileron Norm Page owndesign Mach 1 Rossi 60 power World Championship team 1973 placed fifthtop us position rudder may exchange positions transmitter sticks perfectly acceptable various manufacturers dont always agree pulse comes first did buddy can plug servo receptacle receiver pleases him finding con trol function out place nothing worry about home can bring transmitter antenna near operating transistor portable radio Tune receiver up down dial should hear brrrrr sound between stations Check turning transmitter off sound goes away transmitter putting out signal Another test bring trans mitter next TV operating VHF channel 2 27-MHz transmitters channel 4 72 MHz should hear brrr sound loudspeaker see horizontal black-and-white bars picture may necessary discon nect TV antenna temporarily attach 36-in piece wire TV antenna terminal both see effect have outside tenna TV Another simple check tum transmitter look meter manufacturer supplied needle should its normal position transmitter working Its really surprising people never look meter result forget Transmitter OK System Inoperative Wrap receiver antenna turn around transmitter antenna turn thing can now control ser vos chances receiver crystal broken Remove receiver airplane disconnect everything gather up hold dangling wires remove foam padding hold receiver near ear shake receiver may hear faint tinkle broken crystal positive proof problem replacement crystal can obtained about $8 Make certain replace ment crystal correct receiver because crystals alike though same frequen cy Some receivers use second overtone crystals others use third overtone par ticularly 72-MHz enough variations inhibit trying list Removing replacing crystal simple job anyone has ever done work printed circuit board crystal non-directional may serted either way Retuning may neces sary 98 times 100 isnt usual cautions apply Use 60/40 lead/tin solder rosin-cored 27- 40-Watt 6500F iron minimize heating time avoid creating cold joint pre vious sentence means nothing dont soldering receiver until have built Heathkit some kind some other manufacturers kit Electronic kits usually have very good soldering structions practice get build ing kit will go long way toward protecting investment RC sys tem first kit would suggest Heath IM-18 VTVM about $40 Schlumberger Products Corp PO Box 167 Saint Joseph MI 49085 build wont need multitester de scribed above Back crystal solder new crystal advised September 1976 9 -I Radio Technique can break again being too hasty wire cutter cut off excess pin length Crystals shocksensitive simply bite off end pin dull wire-cutter re sulting shock may snap new crystal inside case Take several small nips working around pin Use sharp tool reasonably careful set will work fine Lets say wrapped receiver antenna around transmitter antenna set still wouldnt play Before doing anything drastic make sure battery voltage getting set Use VTVM multitester expanded-scale volt meter voltage-indicating pilot light Model Aviation April 1976 pg 9 et seq determine voltage available servo receptacles above 44 volts DC Customarily red lead goes k lead goes ining servo pigtail should use same orientation leads test instrument Its unlikely will damage anything get wrong however no voltage getting through check voltage battery plug switch place switch pigtail enters receiver wire may broken along path battery servo See columns Model viation Feb June 76 some hints repairs least likely place find break inside receiver case because red wires black wires usually joined together Transmitter OK Battery Voltage Continuity OK System Inoperative Begin testing servos can use servo stimulator such offered Peter T Walters MA April 76 pp 20-22 can plug another similar set Note word similar cant check World Engines servo Proline system because plugs wont match use different types control signals Servo repairs will dealt later column Everything Else Working Must Receiver Now come hard part trouble receiver isnt broken wire crystal isnt much else simple identify repair specialized tools knowledge can obvious things Ill list 1 Check antenna proper length Usually length about 37 what ever should measure set new write cover owners manual Often piece tenna will lost crash place antenna exits fuselage should always checked because wire often breaks inside insulation spoils tuning reduces sensitivity lets lot interference can easily replace antenna providing have wire same guage same DigiVue tachometer kit discussed article costs $4950 whereas components alone typical commercial tachometers run approxi mately $60 readout digits number strands know length Retuning rarely necessary Most hobby stores electronic supply stores can provide wire need 2 Inspect circuit board jewel er s loupe thing screws eye socket study things up close Look loose components cracks circuit board Most loose components result cold solder joints worked loose due vibration can easily re paired resoldering connection Loose components frequently cause intermittent good bad performance difficult find Patient study strong magnifying glass rock components lightly finger-tip eraser pencil will discover rewards such discovery very gratifyinginstant good performance cracked circuit board acts like loose component because crack usually breaks printed circuit lines gives intermittent connection point fix case solder short piece wire across broken printed wire Once again simple repair very gratifying 3 Tuning least 40 years ago first heard technician say Let novice inside radio screwdriver first thing will tighten screw sight know what Theyre still saying receiver circuit board will observe two cardboard tubes have coils copper wound around outsides little things look like setscrews inside antenna tuning coils will also see three metal boxes similar setscrews acces sible through hole top box intermediate frequency amplifier transformers can adjusted slightly time need im prove sensitivity interference re jection receiver Whether can good adjusting questionable set correctly factory usually sealed bees wax would take tremendous amount vibration disturb great kit-built receivers have examined have rendered useless builders insisted adjusting single time receiver case opened reason builders detailed tuning instructions particular receiver presumably knew what over- doing Now really want tune receiver Let make point usual reason retuning receiver some com ponents have replaced have effect tuning resistors condensers transistors adjustable components themselves Explaining identify need replace such components beyond scope have set partic ular article therefore would please readers would promise resist migh li ly powerful temptation adjust tuning will wont Please continued Digivue Tachometer Ever since digital calculators became cheap people have attracted idea components could re assembled tachometer would continued page 94 10 Model Aviation Slotted heads tuning purposes set screws tightenedthough novice thinks Manufacturer sets correctly usually seals beeswax Radio Technique/Myers continued page 10 read out digits larger number significant digits currently avail able analog instruments Several folks have developed prototype instruments seen mainly around pylon meets commercial digital tachometers available prices around $175 price barrier has hard break since components scratch-built tach ometer usually cost neighborhood $60 order make profit relatively small number sales RC fraternity offers price would larger price RC systems things sat until Modelcraft Electronics PO Box 970 Lomita CA 90717 offered Digivue Tach ometer kit $4950 good friend Bob Aberle W2QPP offered use recently opportunity use field found instrument fits easily hand indicates rpm large bright display Digits about 7/16 high 1/4 wide can seen under lighting conditions except high noon clear sky time some shade wrist necessary can see well enough fly tachometer can see well enough read propeller rpm although found trouble making up its mind under overcast sky discussed problem manufacturer told make sure tachometer could look light-colored background FF Old-Timers/Haught continued page 45 hour needs ten min utes win wind coming up Balsa Board Foot Poring over favorite Old-Timer plan sometimes results some strange least scarce used low-light conditions tried it helped Im sure unit will compared well-proven Heathkit Thumb Tach compared Thumb Tach calibrated 200 rpm units low scale Digivue Tach indicates 100 rpm uncer tainty 50 Id rate about equal margin going Heathkit high scale Heathkit calibrated 1000 rpm units Digivue remains 100 rpm 1 100 Clearly Digivue has accomplished its purpose offers significant digit Heathkit low-light condi tions Heathkit either indicates cor rect rpm nothing Digivue capable locking up wrong answer must exercise some care doubt people would misled once gained some familiarity instrument Heathkit can switched left standing its builtin support use both hands something else As supplied Digivue has switch must held dont like its easy change Overall market tachometer feel either units good buy case hope have now explained benefit have requested schematic diagram digital tachometer dont plan offer column cant beat price boys have requests items would like see column address 70 Froehlich Farm Rd Hicksville NY 11801 balsa sizes times odd sizes further complicated lengths over four ft Perhaps lumber list dream ship runs figures wallet cannot accommodate possible solution problem could looking local lumber yard cities moderate size exists lumber yard carries balsa logs willing special order logs really logs rough sawn boards 4 4 approximately 5 average price locally such log under $5 Densities vary sometimes defect will render portion board unusable part consider able balsa good quality can obtained boards moderate price cut board usable and/or cus tom sizes first have two opposite sides trued up thickness planer Dimensional stock can now cut ordinary table saw using hollow ground blade may have cut both sides thicker pieces avoid overloading saw cut stock slightly oversize finish sanding disc table saw will get considerable balsa dust over thing operation its good cause wont run balsa suppliers out business cutting own will find awkward sizes no longer problem splicing length forgotten curse Scraps make good wing tip blocks other filler pieces dont throw away Old-Timer Event Month020 Replica If have never flown OldTimer before idea kind intrigues 020 Replica painless way try wings speak 020 Replica categorized special event Soci ety Antique Modelers offered nearly Old-Timer contest often included Old-Time event AMA contests SAM defines 020 Replica model gas model kitted plans published prior January 1943 Power restricted 020 engines no minimum weight rules fine kits available through commercial sources Old-Timer possible subject scaled down event fact some old class-A ships al ready right size about 36-in span need beefing down structurally ideal Keep structure same reduce wood sizes save weight Most old class-A ships Y8-in sq 3/16-in sq longerons 3/32-in q will suffice 020 Replica popularity event readily ap parent observing entry lists con tests offering class Some designs course competitive others models have appearing greater numbers Some contests late have dividing Old-Timer Antique categories order provide better com petitive base has move right direction Antique models would defined designed published prior De cember 31 1938 classic designs popularized during period few match later pylon ships would surprised 020 Replica continues grow see further break down between cabin pylon models 020 Replicas usually easy adjust fly require large building benches consume large amounts materials supplies conven ient transport flying field beware contagious truly great way get Old-Timer Just received word Bill Hale Con test Coordinator 10th Annual Na tional Old-Timer Championships held Dayton OH July 31 through August 2 bean fest evening fore July 30 Contact Bill 334 N Remington Rd Columbus OH 43209 enter separate events B C Cabin Pylon plus 30-second Antique 020 Replica Scale Combined Rubber 049 Old-Timer Power free fighters Radio Control events Texaco Antique Class B C Ohio just place years family vaca tion Keep sending cards letters RouteS Box 16 Coeur dAlene ID 83814 94 Model Aviation Lower timer commercial Tatone microswitch added Upper timer DT made ordinary 1-hr kitchen timer Reduces worry
Edition: Model Aviation - 1976/09
Page Numbers: 9, 10, 94
Technique George NI Myers Receiver Repairs HAVE DECIDED am primarily flier Building airplanes repairing models radios something out necessity Therefore have fix radio try simple ways first workbench has oscilloscope vacu um-tube voltmeter assorted signal genera tors other gadgets like special probes above Probably yours doesnt therefore would useless describe techniques require follow ing discussion will emphasize procedures require tools normally found model-builders shop dont have multi-tester Volt-Ohm Meter please get $20 should enough buy good local electronics supply house mail-order shop important thing look DC Voltage scales about 15 6 12 volts full scale sensi tivity 20000 ohms/volt should also have resistance ohms scale shows about 50 ohms center arc has multipliers selec tor switch Xl X 10 X 100 X 1000 XlK Lets begin assuming radio system inoperative did get way radio working fine until crash know enough begin looking crash-type damage check broken crystal broken wires missing antenna other things nature other hand everything working fine last month now wont play begin checking battery packs open shorted cells checking charger make sure its doing its job looking dirt corrosion prevents switch plugs making con tact Whatever do systematically keep records try head can sure will waste time Suppose cant find anything obviously wrong system smart thing to eliminate possibili ties time transmitter putting out signal several ways find out could switch listen scream Im hit dont think flying buddies would appreciate test technique Get frequency pin clothespin same colors flag antenna find somebody set same frequency yours Ask him turn receiver turn transmitter See can make servos move controlled man ner Check ground range should about same used have receiver transmitter fine control functions may show up different places example aileron Norm Page owndesign Mach 1 Rossi 60 power World Championship team 1973 placed fifthtop us position rudder may exchange positions transmitter sticks perfectly acceptable various manufacturers dont always agree pulse comes first did buddy can plug servo receptacle receiver pleases him finding con trol function out place nothing worry about home can bring transmitter antenna near operating transistor portable radio Tune receiver up down dial should hear brrrrr sound between stations Check turning transmitter off sound goes away transmitter putting out signal Another test bring trans mitter next TV operating VHF channel 2 27-MHz transmitters channel 4 72 MHz should hear brrr sound loudspeaker see horizontal black-and-white bars picture may necessary discon nect TV antenna temporarily attach 36-in piece wire TV antenna terminal both see effect have outside tenna TV Another simple check tum transmitter look meter manufacturer supplied needle should its normal position transmitter working Its really surprising people never look meter result forget Transmitter OK System Inoperative Wrap receiver antenna turn around transmitter antenna turn thing can now control ser vos chances receiver crystal broken Remove receiver airplane disconnect everything gather up hold dangling wires remove foam padding hold receiver near ear shake receiver may hear faint tinkle broken crystal positive proof problem replacement crystal can obtained about $8 Make certain replace ment crystal correct receiver because crystals alike though same frequen cy Some receivers use second overtone crystals others use third overtone par ticularly 72-MHz enough variations inhibit trying list Removing replacing crystal simple job anyone has ever done work printed circuit board crystal non-directional may serted either way Retuning may neces sary 98 times 100 isnt usual cautions apply Use 60/40 lead/tin solder rosin-cored 27- 40-Watt 6500F iron minimize heating time avoid creating cold joint pre vious sentence means nothing dont soldering receiver until have built Heathkit some kind some other manufacturers kit Electronic kits usually have very good soldering structions practice get build ing kit will go long way toward protecting investment RC sys tem first kit would suggest Heath IM-18 VTVM about $40 Schlumberger Products Corp PO Box 167 Saint Joseph MI 49085 build wont need multitester de scribed above Back crystal solder new crystal advised September 1976 9 -I Radio Technique can break again being too hasty wire cutter cut off excess pin length Crystals shocksensitive simply bite off end pin dull wire-cutter re sulting shock may snap new crystal inside case Take several small nips working around pin Use sharp tool reasonably careful set will work fine Lets say wrapped receiver antenna around transmitter antenna set still wouldnt play Before doing anything drastic make sure battery voltage getting set Use VTVM multitester expanded-scale volt meter voltage-indicating pilot light Model Aviation April 1976 pg 9 et seq determine voltage available servo receptacles above 44 volts DC Customarily red lead goes k lead goes ining servo pigtail should use same orientation leads test instrument Its unlikely will damage anything get wrong however no voltage getting through check voltage battery plug switch place switch pigtail enters receiver wire may broken along path battery servo See columns Model viation Feb June 76 some hints repairs least likely place find break inside receiver case because red wires black wires usually joined together Transmitter OK Battery Voltage Continuity OK System Inoperative Begin testing servos can use servo stimulator such offered Peter T Walters MA April 76 pp 20-22 can plug another similar set Note word similar cant check World Engines servo Proline system because plugs wont match use different types control signals Servo repairs will dealt later column Everything Else Working Must Receiver Now come hard part trouble receiver isnt broken wire crystal isnt much else simple identify repair specialized tools knowledge can obvious things Ill list 1 Check antenna proper length Usually length about 37 what ever should measure set new write cover owners manual Often piece tenna will lost crash place antenna exits fuselage should always checked because wire often breaks inside insulation spoils tuning reduces sensitivity lets lot interference can easily replace antenna providing have wire same guage same DigiVue tachometer kit discussed article costs $4950 whereas components alone typical commercial tachometers run approxi mately $60 readout digits number strands know length Retuning rarely necessary Most hobby stores electronic supply stores can provide wire need 2 Inspect circuit board jewel er s loupe thing screws eye socket study things up close Look loose components cracks circuit board Most loose components result cold solder joints worked loose due vibration can easily re paired resoldering connection Loose components frequently cause intermittent good bad performance difficult find Patient study strong magnifying glass rock components lightly finger-tip eraser pencil will discover rewards such discovery very gratifyinginstant good performance cracked circuit board acts like loose component because crack usually breaks printed circuit lines gives intermittent connection point fix case solder short piece wire across broken printed wire Once again simple repair very gratifying 3 Tuning least 40 years ago first heard technician say Let novice inside radio screwdriver first thing will tighten screw sight know what Theyre still saying receiver circuit board will observe two cardboard tubes have coils copper wound around outsides little things look like setscrews inside antenna tuning coils will also see three metal boxes similar setscrews acces sible through hole top box intermediate frequency amplifier transformers can adjusted slightly time need im prove sensitivity interference re jection receiver Whether can good adjusting questionable set correctly factory usually sealed bees wax would take tremendous amount vibration disturb great kit-built receivers have examined have rendered useless builders insisted adjusting single time receiver case opened reason builders detailed tuning instructions particular receiver presumably knew what over- doing Now really want tune receiver Let make point usual reason retuning receiver some com ponents have replaced have effect tuning resistors condensers transistors adjustable components themselves Explaining identify need replace such components beyond scope have set partic ular article therefore would please readers would promise resist migh li ly powerful temptation adjust tuning will wont Please continued Digivue Tachometer Ever since digital calculators became cheap people have attracted idea components could re assembled tachometer would continued page 94 10 Model Aviation Slotted heads tuning purposes set screws tightenedthough novice thinks Manufacturer sets correctly usually seals beeswax Radio Technique/Myers continued page 10 read out digits larger number significant digits currently avail able analog instruments Several folks have developed prototype instruments seen mainly around pylon meets commercial digital tachometers available prices around $175 price barrier has hard break since components scratch-built tach ometer usually cost neighborhood $60 order make profit relatively small number sales RC fraternity offers price would larger price RC systems things sat until Modelcraft Electronics PO Box 970 Lomita CA 90717 offered Digivue Tach ometer kit $4950 good friend Bob Aberle W2QPP offered use recently opportunity use field found instrument fits easily hand indicates rpm large bright display Digits about 7/16 high 1/4 wide can seen under lighting conditions except high noon clear sky time some shade wrist necessary can see well enough fly tachometer can see well enough read propeller rpm although found trouble making up its mind under overcast sky discussed problem manufacturer told make sure tachometer could look light-colored background FF Old-Timers/Haught continued page 45 hour needs ten min utes win wind coming up Balsa Board Foot Poring over favorite Old-Timer plan sometimes results some strange least scarce used low-light conditions tried it helped Im sure unit will compared well-proven Heathkit Thumb Tach compared Thumb Tach calibrated 200 rpm units low scale Digivue Tach indicates 100 rpm uncer tainty 50 Id rate about equal margin going Heathkit high scale Heathkit calibrated 1000 rpm units Digivue remains 100 rpm 1 100 Clearly Digivue has accomplished its purpose offers significant digit Heathkit low-light condi tions Heathkit either indicates cor rect rpm nothing Digivue capable locking up wrong answer must exercise some care doubt people would misled once gained some familiarity instrument Heathkit can switched left standing its builtin support use both hands something else As supplied Digivue has switch must held dont like its easy change Overall market tachometer feel either units good buy case hope have now explained benefit have requested schematic diagram digital tachometer dont plan offer column cant beat price boys have requests items would like see column address 70 Froehlich Farm Rd Hicksville NY 11801 balsa sizes times odd sizes further complicated lengths over four ft Perhaps lumber list dream ship runs figures wallet cannot accommodate possible solution problem could looking local lumber yard cities moderate size exists lumber yard carries balsa logs willing special order logs really logs rough sawn boards 4 4 approximately 5 average price locally such log under $5 Densities vary sometimes defect will render portion board unusable part consider able balsa good quality can obtained boards moderate price cut board usable and/or cus tom sizes first have two opposite sides trued up thickness planer Dimensional stock can now cut ordinary table saw using hollow ground blade may have cut both sides thicker pieces avoid overloading saw cut stock slightly oversize finish sanding disc table saw will get considerable balsa dust over thing operation its good cause wont run balsa suppliers out business cutting own will find awkward sizes no longer problem splicing length forgotten curse Scraps make good wing tip blocks other filler pieces dont throw away Old-Timer Event Month020 Replica If have never flown OldTimer before idea kind intrigues 020 Replica painless way try wings speak 020 Replica categorized special event Soci ety Antique Modelers offered nearly Old-Timer contest often included Old-Time event AMA contests SAM defines 020 Replica model gas model kitted plans published prior January 1943 Power restricted 020 engines no minimum weight rules fine kits available through commercial sources Old-Timer possible subject scaled down event fact some old class-A ships al ready right size about 36-in span need beefing down structurally ideal Keep structure same reduce wood sizes save weight Most old class-A ships Y8-in sq 3/16-in sq longerons 3/32-in q will suffice 020 Replica popularity event readily ap parent observing entry lists con tests offering class Some designs course competitive others models have appearing greater numbers Some contests late have dividing Old-Timer Antique categories order provide better com petitive base has move right direction Antique models would defined designed published prior De cember 31 1938 classic designs popularized during period few match later pylon ships would surprised 020 Replica continues grow see further break down between cabin pylon models 020 Replicas usually easy adjust fly require large building benches consume large amounts materials supplies conven ient transport flying field beware contagious truly great way get Old-Timer Just received word Bill Hale Con test Coordinator 10th Annual Na tional Old-Timer Championships held Dayton OH July 31 through August 2 bean fest evening fore July 30 Contact Bill 334 N Remington Rd Columbus OH 43209 enter separate events B C Cabin Pylon plus 30-second Antique 020 Replica Scale Combined Rubber 049 Old-Timer Power free fighters Radio Control events Texaco Antique Class B C Ohio just place years family vaca tion Keep sending cards letters RouteS Box 16 Coeur dAlene ID 83814 94 Model Aviation Lower timer commercial Tatone microswitch added Upper timer DT made ordinary 1-hr kitchen timer Reduces worry
Edition: Model Aviation - 1976/09
Page Numbers: 9, 10, 94
Technique George NI Myers Receiver Repairs HAVE DECIDED am primarily flier Building airplanes repairing models radios something out necessity Therefore have fix radio try simple ways first workbench has oscilloscope vacu um-tube voltmeter assorted signal genera tors other gadgets like special probes above Probably yours doesnt therefore would useless describe techniques require follow ing discussion will emphasize procedures require tools normally found model-builders shop dont have multi-tester Volt-Ohm Meter please get $20 should enough buy good local electronics supply house mail-order shop important thing look DC Voltage scales about 15 6 12 volts full scale sensi tivity 20000 ohms/volt should also have resistance ohms scale shows about 50 ohms center arc has multipliers selec tor switch Xl X 10 X 100 X 1000 XlK Lets begin assuming radio system inoperative did get way radio working fine until crash know enough begin looking crash-type damage check broken crystal broken wires missing antenna other things nature other hand everything working fine last month now wont play begin checking battery packs open shorted cells checking charger make sure its doing its job looking dirt corrosion prevents switch plugs making con tact Whatever do systematically keep records try head can sure will waste time Suppose cant find anything obviously wrong system smart thing to eliminate possibili ties time transmitter putting out signal several ways find out could switch listen scream Im hit dont think flying buddies would appreciate test technique Get frequency pin clothespin same colors flag antenna find somebody set same frequency yours Ask him turn receiver turn transmitter See can make servos move controlled man ner Check ground range should about same used have receiver transmitter fine control functions may show up different places example aileron Norm Page owndesign Mach 1 Rossi 60 power World Championship team 1973 placed fifthtop us position rudder may exchange positions transmitter sticks perfectly acceptable various manufacturers dont always agree pulse comes first did buddy can plug servo receptacle receiver pleases him finding con trol function out place nothing worry about home can bring transmitter antenna near operating transistor portable radio Tune receiver up down dial should hear brrrrr sound between stations Check turning transmitter off sound goes away transmitter putting out signal Another test bring trans mitter next TV operating VHF channel 2 27-MHz transmitters channel 4 72 MHz should hear brrr sound loudspeaker see horizontal black-and-white bars picture may necessary discon nect TV antenna temporarily attach 36-in piece wire TV antenna terminal both see effect have outside tenna TV Another simple check tum transmitter look meter manufacturer supplied needle should its normal position transmitter working Its really surprising people never look meter result forget Transmitter OK System Inoperative Wrap receiver antenna turn around transmitter antenna turn thing can now control ser vos chances receiver crystal broken Remove receiver airplane disconnect everything gather up hold dangling wires remove foam padding hold receiver near ear shake receiver may hear faint tinkle broken crystal positive proof problem replacement crystal can obtained about $8 Make certain replace ment crystal correct receiver because crystals alike though same frequen cy Some receivers use second overtone crystals others use third overtone par ticularly 72-MHz enough variations inhibit trying list Removing replacing crystal simple job anyone has ever done work printed circuit board crystal non-directional may serted either way Retuning may neces sary 98 times 100 isnt usual cautions apply Use 60/40 lead/tin solder rosin-cored 27- 40-Watt 6500F iron minimize heating time avoid creating cold joint pre vious sentence means nothing dont soldering receiver until have built Heathkit some kind some other manufacturers kit Electronic kits usually have very good soldering structions practice get build ing kit will go long way toward protecting investment RC sys tem first kit would suggest Heath IM-18 VTVM about $40 Schlumberger Products Corp PO Box 167 Saint Joseph MI 49085 build wont need multitester de scribed above Back crystal solder new crystal advised September 1976 9 -I Radio Technique can break again being too hasty wire cutter cut off excess pin length Crystals shocksensitive simply bite off end pin dull wire-cutter re sulting shock may snap new crystal inside case Take several small nips working around pin Use sharp tool reasonably careful set will work fine Lets say wrapped receiver antenna around transmitter antenna set still wouldnt play Before doing anything drastic make sure battery voltage getting set Use VTVM multitester expanded-scale volt meter voltage-indicating pilot light Model Aviation April 1976 pg 9 et seq determine voltage available servo receptacles above 44 volts DC Customarily red lead goes k lead goes ining servo pigtail should use same orientation leads test instrument Its unlikely will damage anything get wrong however no voltage getting through check voltage battery plug switch place switch pigtail enters receiver wire may broken along path battery servo See columns Model viation Feb June 76 some hints repairs least likely place find break inside receiver case because red wires black wires usually joined together Transmitter OK Battery Voltage Continuity OK System Inoperative Begin testing servos can use servo stimulator such offered Peter T Walters MA April 76 pp 20-22 can plug another similar set Note word similar cant check World Engines servo Proline system because plugs wont match use different types control signals Servo repairs will dealt later column Everything Else Working Must Receiver Now come hard part trouble receiver isnt broken wire crystal isnt much else simple identify repair specialized tools knowledge can obvious things Ill list 1 Check antenna proper length Usually length about 37 what ever should measure set new write cover owners manual Often piece tenna will lost crash place antenna exits fuselage should always checked because wire often breaks inside insulation spoils tuning reduces sensitivity lets lot interference can easily replace antenna providing have wire same guage same DigiVue tachometer kit discussed article costs $4950 whereas components alone typical commercial tachometers run approxi mately $60 readout digits number strands know length Retuning rarely necessary Most hobby stores electronic supply stores can provide wire need 2 Inspect circuit board jewel er s loupe thing screws eye socket study things up close Look loose components cracks circuit board Most loose components result cold solder joints worked loose due vibration can easily re paired resoldering connection Loose components frequently cause intermittent good bad performance difficult find Patient study strong magnifying glass rock components lightly finger-tip eraser pencil will discover rewards such discovery very gratifyinginstant good performance cracked circuit board acts like loose component because crack usually breaks printed circuit lines gives intermittent connection point fix case solder short piece wire across broken printed wire Once again simple repair very gratifying 3 Tuning least 40 years ago first heard technician say Let novice inside radio screwdriver first thing will tighten screw sight know what Theyre still saying receiver circuit board will observe two cardboard tubes have coils copper wound around outsides little things look like setscrews inside antenna tuning coils will also see three metal boxes similar setscrews acces sible through hole top box intermediate frequency amplifier transformers can adjusted slightly time need im prove sensitivity interference re jection receiver Whether can good adjusting questionable set correctly factory usually sealed bees wax would take tremendous amount vibration disturb great kit-built receivers have examined have rendered useless builders insisted adjusting single time receiver case opened reason builders detailed tuning instructions particular receiver presumably knew what over- doing Now really want tune receiver Let make point usual reason retuning receiver some com ponents have replaced have effect tuning resistors condensers transistors adjustable components themselves Explaining identify need replace such components beyond scope have set partic ular article therefore would please readers would promise resist migh li ly powerful temptation adjust tuning will wont Please continued Digivue Tachometer Ever since digital calculators became cheap people have attracted idea components could re assembled tachometer would continued page 94 10 Model Aviation Slotted heads tuning purposes set screws tightenedthough novice thinks Manufacturer sets correctly usually seals beeswax Radio Technique/Myers continued page 10 read out digits larger number significant digits currently avail able analog instruments Several folks have developed prototype instruments seen mainly around pylon meets commercial digital tachometers available prices around $175 price barrier has hard break since components scratch-built tach ometer usually cost neighborhood $60 order make profit relatively small number sales RC fraternity offers price would larger price RC systems things sat until Modelcraft Electronics PO Box 970 Lomita CA 90717 offered Digivue Tach ometer kit $4950 good friend Bob Aberle W2QPP offered use recently opportunity use field found instrument fits easily hand indicates rpm large bright display Digits about 7/16 high 1/4 wide can seen under lighting conditions except high noon clear sky time some shade wrist necessary can see well enough fly tachometer can see well enough read propeller rpm although found trouble making up its mind under overcast sky discussed problem manufacturer told make sure tachometer could look light-colored background FF Old-Timers/Haught continued page 45 hour needs ten min utes win wind coming up Balsa Board Foot Poring over favorite Old-Timer plan sometimes results some strange least scarce used low-light conditions tried it helped Im sure unit will compared well-proven Heathkit Thumb Tach compared Thumb Tach calibrated 200 rpm units low scale Digivue Tach indicates 100 rpm uncer tainty 50 Id rate about equal margin going Heathkit high scale Heathkit calibrated 1000 rpm units Digivue remains 100 rpm 1 100 Clearly Digivue has accomplished its purpose offers significant digit Heathkit low-light condi tions Heathkit either indicates cor rect rpm nothing Digivue capable locking up wrong answer must exercise some care doubt people would misled once gained some familiarity instrument Heathkit can switched left standing its builtin support use both hands something else As supplied Digivue has switch must held dont like its easy change Overall market tachometer feel either units good buy case hope have now explained benefit have requested schematic diagram digital tachometer dont plan offer column cant beat price boys have requests items would like see column address 70 Froehlich Farm Rd Hicksville NY 11801 balsa sizes times odd sizes further complicated lengths over four ft Perhaps lumber list dream ship runs figures wallet cannot accommodate possible solution problem could looking local lumber yard cities moderate size exists lumber yard carries balsa logs willing special order logs really logs rough sawn boards 4 4 approximately 5 average price locally such log under $5 Densities vary sometimes defect will render portion board unusable part consider able balsa good quality can obtained boards moderate price cut board usable and/or cus tom sizes first have two opposite sides trued up thickness planer Dimensional stock can now cut ordinary table saw using hollow ground blade may have cut both sides thicker pieces avoid overloading saw cut stock slightly oversize finish sanding disc table saw will get considerable balsa dust over thing operation its good cause wont run balsa suppliers out business cutting own will find awkward sizes no longer problem splicing length forgotten curse Scraps make good wing tip blocks other filler pieces dont throw away Old-Timer Event Month020 Replica If have never flown OldTimer before idea kind intrigues 020 Replica painless way try wings speak 020 Replica categorized special event Soci ety Antique Modelers offered nearly Old-Timer contest often included Old-Time event AMA contests SAM defines 020 Replica model gas model kitted plans published prior January 1943 Power restricted 020 engines no minimum weight rules fine kits available through commercial sources Old-Timer possible subject scaled down event fact some old class-A ships al ready right size about 36-in span need beefing down structurally ideal Keep structure same reduce wood sizes save weight Most old class-A ships Y8-in sq 3/16-in sq longerons 3/32-in q will suffice 020 Replica popularity event readily ap parent observing entry lists con tests offering class Some designs course competitive others models have appearing greater numbers Some contests late have dividing Old-Timer Antique categories order provide better com petitive base has move right direction Antique models would defined designed published prior De cember 31 1938 classic designs popularized during period few match later pylon ships would surprised 020 Replica continues grow see further break down between cabin pylon models 020 Replicas usually easy adjust fly require large building benches consume large amounts materials supplies conven ient transport flying field beware contagious truly great way get Old-Timer Just received word Bill Hale Con test Coordinator 10th Annual Na tional Old-Timer Championships held Dayton OH July 31 through August 2 bean fest evening fore July 30 Contact Bill 334 N Remington Rd Columbus OH 43209 enter separate events B C Cabin Pylon plus 30-second Antique 020 Replica Scale Combined Rubber 049 Old-Timer Power free fighters Radio Control events Texaco Antique Class B C Ohio just place years family vaca tion Keep sending cards letters RouteS Box 16 Coeur dAlene ID 83814 94 Model Aviation Lower timer commercial Tatone microswitch added Upper timer DT made ordinary 1-hr kitchen timer Reduces worry