Gibson_ga_40_55_later 电路图 维修原理图.pdf
en l Z 0, - ,. -:I: u - 0 0 N <: <: .J <: . U Z - Z 0 en m - 0 C) 0 0 . IN ., - 收音机爱好者资料库 Ra d i o Fa n s .CN ) 10 j10k 170 k. .0; II- 10 lOOK 收音机爱好者资料库 Ra d i o Fa n s .CN - _J FIGUREA OPERATIONOFINSTRUMENT Whenoneor twoinstrumentsarepluggedintothejacksmarked Instruments,threestagesof.amplificationare.used.Thetotal gainof bothcircuitsbeingset=withthecontrolmarkedInstruments. ThetwojacksmarkedMICROPHONEor INSTRUMENTSmayalsobe usedwithanyof theGIBSONelectricalinstruments.Whenused thiswaya carefulsettingof the volumecontrolmarkedMICROPHONE mustbe madeto avoidoverloadandconsequentdistortion.This adjustmentcanbeeasilymadeby turningthevolumecontrolon the guitaror otherinstrumentallthe wayon andsettingtheMICROPHONE controlat thepointwherenodistortionoccurswhenthestrings arestruckwithmaximumforce.Byutilizingthe MICROPHONEsocket in thiswaytwomoreinstrumentscanbepluggedin, making_total of fourelectricalinstrumentswhichmaybeusedandblended) Thevoicingcontrolcircuitforthisamplifierhasbeen! s4.=gnedive. t-pWay.erc:<an<ext-rcell1ed:dgona.l_c:9r:rr coloring. OPERATIONOF THEMICROPHONE Becauseof thehighpoweroutput,highgainandhighfidelity characteristicsof theGIBSONGA-40Amplifierit makesanexcep- tionallyfinepublicaddresssystemwhenusedwitheitherthe crystal,dynamicor velocitytypesof microphones. Whiletheamplifierwilloperateverywellwithanyofthe crystal.mediumor highimpedancedynamicor velocity(ribbon) microphones,it is recommendedthat.beforeinvestingin a micro- phone.youconsultyourGIBSONdealer.AuthorizedGIBSONdealers cansupplyyouwitha microphonewhichhasbeenselectedand matchedtothe amplifier,thusinsuringthe mostfaithfulrepro- ductionof voiceand music. Whenusinga microphoneit is importantthattheGIBSON75A orsimilarshieldedplugbeattachedtothecord.Theordinary phoneplug withbakeliteor othernon-shieldedcoveris notsuit- ablebecausetheleadsfromthemicrophonemustbecompletely shielded.Otherwiseobjectionablehum willresult.FigureA illustratestheproperwaytoconnecttheplugto themicrophone cable.Tousethemicrophone,nserttheplugin the MICROPHONE jackandadvancethe MICROPHONEvolumecontroluntila feedback squealor howlis producedintheloudspeaker.Reducethevolume controltojustbelowthefeed-backpoint.Thissettingwill varyconsiderablydependinguponthesizeof theroom.itsacousti- calpropertiesandthedistancebetweenthemicrophoneandloud- speaker.Feedbackis thelimitingfactorin allpublicaddress (over) 收音机爱好者资料库 Ra d i o Fa n s .CN OPERATIONOF THEMICROPHONE(Contd) installationsandis causedwhenthelevelofsoundfromtheloud- speakersis sufficientto actuatethe microphone.Thegeneralrule whensettinguptheequipmentis to placetheloudspeakerasfar fromthe microphoneaspossible. ThevolumecontrolsINSTRUMENTSand ICROPHONE,beingcom- pletelyindependentof eachother,allowtheinputsfromthevariou sourcesto be mixed or blended.Becauseofthisflexibilitymany unusualeffectscanbeeasilyworkedout. Ifthe MICROPHONEjacksarenotin useturnthe MICROPHONE volumecontrolallthe wayoff. TREMOLO Thetremoloeffectis turnedon andoffby meansofa foot switchof thepushbuttontype.TheTremolofrequencyofthe amplifieris controlledbythepointerknobmarkedFrequency. Theminimumandmaximumspeedhasbeencarefullysetto covera wide rangeof tremoloeffects.Thedepthof thetremolomaybevaried bythepointerknobmarkedDepth. GENERAL Amplifiersarecarefullypackedto preventdamageinshipment. However,uponreceiptof theamplifier,lookit overcarefullyto makesuretherehasbeennobreakageof tubesor parts.If you findthatdamagehasoccurredduringshipment,wesuggesttheTrans- portationCompanybe calledimmediately,anda claimplaced. CAUTION Damageto theamplifierwillresultifit is connectedto an improperpowersource.Thisamplifieris designedto beoperatedon 105-125volt,50-60cyclealternatingcurrentonly.Makesurethe voltagefromthepowerlinesis notover125,andthatthefrequency of thecurrentis either50or 60 cycles.Whenreadytoturnon power,plugthepowercordintotheelectricoutletandturnon theswitch.Waitapproximatelyone minuteforthetubesto heat, andtheamplifieris readyforuse. TUBES Besuretubesarein theirproperpositionsbeforeplacing theamplifierin operation.Alltubeshavebeentestedandproved satisfactorybeforeshipment. SERVICE If theamplifieris in needof servicing,wesuggestit be takentoa reliableradioman.Theelectricaldiagramattached shouldbe showntherepairmanto assisthimin servicingtheamplifier. * Thefuseusedin theGA-40amplifieris a typeAGofthreeampere rating.DONOTUSEFUSESOFHIGHERRATING.
