Roberts-A901-tape-sm 维修电路原理图.pdf

crl!-d6a=+Er l- r+lL ViROBERTS MODELS A.9OI.9q, gO-C,9O-S7 L/ 2l:psL/ 2 HourI Hour5o .i,tnod6o.)sd|JlEgood,noEtElaiEoFola&PI9GENERAL INFO RMAT IONRoberts Models 90, 90-S, and 90-C tape recorders consist of two basic sections - atape-transport mechanism and a record-playback amplifier.The Model 90 is a monaural tape recorder. Models 90-S and 90-C are stereo tape re-corders. Stereo can be recorded by connecting a Roberts Model A-901 stereo amplifier tojack 2 on the stereo tape recorders. On the Model 90-C, a preamplifier is included for thelower channel.The mechanical controls are interlocked to prevent accidental selection of an incorrectoperating mode. rThe Roberts tape recorders have two speeds, 7 L/ 2 and 3 3/ 4 ips. With both monauraltracks, the recording times are as follows:Reel Size5 (600 ft. )? (1200 ft. )3 3/4IpsI Hour2 HoursThese models are designed to operate on 60 cycles, lI0-120 volts AC only.Supplied by:Roberts Electronics, lnc.1028 North La Brea AvenueHollywood 38, CaliforniaThis msterial compiled and pvblished byHOWARD f. SAtnS & CO., lNC., INDIANAPOtIS 6, INDIANAcQ40?Copyright 1960 . All Rights Reservedc-2Frl-f5L.IC.5r-reFEFrl-dc+DATE 2 - $OsET 473F00ER 13IPnoroFAcr FolJth&gn+*:.1*Y.;ffi-ffiRadioFans.CN 收音机爱 好者资料库l.2.Remove lid from camying case.Remove microphone and AC supply cord fromstorage compartment on left side of canying0n-0ff SwitchOn the Model g0, tis is a 2-position switch.When it is in the On position, power is turned on tothe amplifier and tape deck. On the Models g0-S and90-C, it is a 3-position switch. When the switch ispushed to the AII On position, power is turned on tothe amplifier and tape deck. When it is in the Amp Offposition, power is applied to the tape deck only. TheOff position turns the power off to the entire unit.Vol umeTurning this control clockwise increases thevolume in either record or playback. Turning itcounterclockwise decreases the volume in either re-cord or playback.ToneThis control firnctions inplayback only. Turningit clockwise from position 5 will increase the trebleresponse; turning it counterclockwise from position bwill attenuate tie response.Play-Record and Record LockThis is a 3-position control: Stop, play, andOPERAT INGThreading the Tapel. Place a full reel of tape on feed reel spindle(6?), making certain the reel slots engage theprotrusions on the pan. place an empty reelon take-up spindle (2?), again making certainthe slots engage the protrusions on thJpan.2. Unwind about 14 inches of tape from the supplyreel. Hold a section of tape taut and insert intothe tape slot, making sure the dull-coated sidefaces the rear of the recorder.3. Insertthe freeendof thetape intooneofthe slotsinthe hub of the take-up reel. While holding theend in place, turn the reel two orthree times tosecure tte tape to the reel.To Make a Monaural RecordingI. P-lug a microphone into the Microphone jack, orplace a signal from some other sburce into treLine Input jack.2. Depress the Record Lock and simultaneouslyturn the Play-Record control to ttre Record po_sition.3. Adjust the Volume control until the averagereading on the VU meter is -b.Page 2P REPAR ING FO R O PERAT IONcase.3. Make certain alltion-controls are in the Stop posi-FUNCTIONS OF CONTROLSRecord. Turning this control clockwise from the Stopposition places the unit in ptay. Depressing the RecordLock and turning the control to the Record position atthe same time, places the unit in Record.NOTE: This control is interlocked with the Wind-Rewind control. It must be in the Stop positionbef ore ttte Wind -Rewind c ontrol can be op e rated.Wind-RewindTurning this controlto the left places tlreunit inttte Wind position; to the right, in the Rewind position.NOTE: This control is interlocked with the play-Record control. It must be in the Stop positionbefore the play-Record control can be operated.PauseWhen this lever is raised, pressure is removedfrom the drive capstan, and the take-up reel is dis_engaged. This permits spot editing and momentarystops.NOTE: This control is not on the Model g0.INSTRUCTIONSCAUTION: Do not connect a speaker or other low-impedance load to the Output jack while makinga recording.To Make a Stereo Recordingl. Connect the interconnecting cable from theChannel-2 head jack to the stereo channel intheModel 4-901 amplifier.2. Move the On-Off switch on the tape recorder toAII On. Move the On-Off switchon theamplifierto On.3. Turn the Volume control until the VU meterreads -5.4. PIug microphones into the Microphone Inputjacks, orplace signals from another sourceintotte Line Input jacks.5. Depress the Record Lock and simultaneouslyturn the Record-play control on the tape trans_port to Record.6. PlacethePlay-Record switchon A-g0Iamplifierin Record.?. On Model 90-C, turn the switch on the built_inpreamplifier, on bottom of the case, to Out.RadioFans.CN 收音机爱 好者资料库FIG. I TOP VIEW OF MECHANISM WITH ESCUTCHEON REMOVED.FoEtTta8gFourti 7FIt/lonaural Playback1. Thread the tape (see Threading the Tape).2. Turn the unit on and allow a few seconds for itto warm up.3. Turn the Play-Record control to Play.4. Adjustthe volume andtone to thedesired listen-ing leveI.Stereo Playbackl. Thread the tape (see Threading the Tape).2. Turn the tape recorder switch to Alt On. Turnthe A-90I amplifier switch to In.3. Connect the interconnecting cable from theChannel-2 jack of the tape recorderto the Stereojack on the amplifier.4. Make certain the Play-Record switch on theamplifier is in Play.5. Turn the Play-Record controlon the tapetrans-port to Play.6. Adjust theVolume controls onthe tape recorderand amplifier to a balanced output.Speed ChangeTo change the tape from 7 V 2 to 3 3/ 4 ips, re-move the thumbscrew and bushing from the capstan.When the bushing is not being used, store it on thebushing post.lndex CounterAfter atape is threaded onthe recorder, set theIndex Counter to 000. The index numbers can thenbe noted at the beginning of each selection, for futurereference.External SpeakerAn external speaker may be plugged into theOutput jack. The internal speakerwill be fusconnectedwhen using an external speaker.Erasing TapeTo erase one track of a tape, turn the knob ontop of the head clockwise. This raises the erase headtothe half-track position. To erase both tracks at thesame time, turn the knob counterclockwise. ThisIowersthe erase headto the full-track position. Whenthe unit is in the Record position, the erase head isautomatically positioned before a new recording ismade. To erase the tape without putting a new re-cording on it, turn the volume to minimum and thePlay-Record control to Record.To Use the Second Track (ltylonauralll. Turn the Play-Record control to Stop.nOInu)Page 3II2.3.Remove the reel containing the tape, and placeit on the left (supply) reel spindle.Place the empty reel on the right (take-up) reelspindle.To Remove Tape Transport Mechanisn from CaseI. Remove the two screws in the spindle pans (onein each pan),2. Remove the two screws holding tle dress plate,and remove the dressplate.3. Remove one screw on the right side of the es-cutcheon and the 7 V2-tps bushlng from the leftside.Remove the pressure roller.Remove the Play-Record and Wind-Rewindknobs.Remove the escutcheon.Remove the four screws holding the tape trans-port to the case.Unplug all connections to the tape transport andspeaker, and lift the tape transport from thecase.9. To reassemble, reverse the foregoing proce-dure.To Remove Amplifier from Casel. Remove the four screws holding the amplilierand escutcheon to the case.2. Unplug all connecting plugs.Record-Playback Head Alignment With StandardAlignment Tapel. Thread the tape (see Threading the Tape).2. Connect a 0.5-volt AC voltmeter to a standardphono plug, and insert the plug into the Outputjack.3, Turn the Tone control to maximum.4. Remove thetwoscrews fromthehead cover, andremove the head cover.5. Insert a screwdriver, through the hole in thehead shield, into the alignment screrr.6. Play back thetape at full volume, and rotate the4. Thread the tape, and proceed with the recordingas described under To Make a Monaural Re-cording. D ISASSEMBLYADJUSTMENTSLU BR ICAT IONLift the amplifier from the case.To reassemble, reverse the foregoing proce-dure.To Renove Prean:p fron Case on A4odel 90-Cl. Remove the two screws from the bottom of thecase,2. Unplug aII connecting plugs.3. Lift the preamp from the case.4. To reassemble, reverse the foregoing proce-dure.To Remove Model A-901 Anplifier fron, Casel. Remove the four screws holding the amplifierto the case.2. Remove the four screws holding the speakercover on,3. Disconnect the speaker.4. Feed theAC cord throughthe hole inthe storagecompartment.5. Lift ttre amplifier from the case.6. To reassemble, reverse the foregoing proce-cure.3.4.4.5.6.t -8.alignment screw in either direction until the10,000-cycle note givesthe highest meter read-ing.Record-Playback Head Alignment With Con mercialMusic Tape1. Thread the tape (see Threading the Tape).2. PLay back the tape at a normal listening level,and adjust the head alignment screw for maxi-mum clarity of high-pitched instruments.Brake ShoesWhen brake shoes (34) and (80) become worn,loosen the mounting screws and rotate the shoes afew degrees until a new braking surface is exposed.Lubricate the following parts every three monthsPage 4in heavy service, every six months in moderate ser-ffi-ii,:.,_.rN,tvrtl.:.:!F.-lffii:-;i-,.,.1r,:#;*:. . . .f* - rrlr :.-L&+ff*. tt,ilrffiffi,fr# $o$ &#F IG. 2 BOTTOM V IEW OF MECHAN I SM.FotptTlaisFolatit p9vice, or once a year in light service, as follows:l. Feed and take-up reel spindle shafts, with twodrops of light machine oil on each shaft.2. Rewind idler bearing and wind take-up idlerbearing, with two drops of Iight machine oil oneach bearing.3. Apply a liberal amount of light machine greaseto drive idler bearing bore.Saturate thefelt washer in the chrome retainingcup of.the drive capstan with light machine oil.Apply a liberal amount of light machine greaseto each roller on all levers and cams.Themotor bearings are lubricated andsealed atthe factory and need no further lubrication.4.5.6.Most defects, other than wear or breakage, canbe traced todirty surfaces. The recording head, cap-stan, and pinch wheel (4) may accumulate tape coatingresidue, which is worn off the tape as it passes theseparts. Remove this accumulation periodically, be-cause it may cause faint recording and poor playback.Clean these parts with a soft cotton swab soaked inalcohol.CLEAN INGTROUBLE CHARTSYMPTOMCAUSEREMEDYMotordoes notrun, and pilotlight does not light.AC cord disconnected.Fuse blown.Connect AC cord.Replace fuse.I.tl.2.Distorted recordings andpoor erase.I. Bias oscillator tube defec-tive.l. Replace bias oscillator tube.Pilot light lights, motor runs,but no record or play.t. Speaker wires disconnectedor broken.l. Connect or replace speakerwires.Ocfnt)I/Speaker hum at fuII volume.I. Head cable disconnected.t. Reconnect head cable.Page 5TROU BLE CHART (CONT )SYMPTOMCAUSEREMEDYMotorruns. pilotlightlights, I. Defective rectifier tube. I. Replace rectifier tube.no record or playback, no; speaker hum, and VU meter 2. Defective output tube. 2. Replace output tribe.does not read on record.No record or playfack, but l. Preamplifier tube defective. I. Replace preamplifier tube.slight speaker hum variablewith volume control.Noisy playbackor poorhigh- I. Heads misaligned. I. See Head Alignment. frequency response.2, Heads magnetized. 2. Dernagnetize heads.Wow or flutter at? L/2-ips 1. Speed change bushing slip- l. Tighten screw (120).speed. ping on shaft.lnsufficientdrive at? L/ 2-or I. Defective main drive idler l. Replace main drive idler3 3/4-ips speeds. wheel (3i). wheel (3I).2. Oil on capstan. 2. See Cleaning. 3. Main drive belt (8) defec- 3. Replace main drive beft (IlB).tive.4. Drive motor(I24)or starting 4. Replace drive motor (I24) orcapacitor defective. starting capacitor.Tape spills when going f rom I. Reel diameters unequal. l. Tape reels mustbave the samewind or rewind to stop. diameter.2. Brake shoes (34) and (80) 2. Replace oradjust brake shoesworn or out of adjustment. (3a) and (80).lndex Counter does not I. Counter belt (I27) worn or l. Replace counter belt (127).function. broken.MECHANICAL PARTS LISTRef .No-PartNo.DescriptionI234567I9l0nt2l3t4l5r6l?t8l92020A2T90-50-4390-50-r590-50-4790-50-6490-52-2790-50-1690-3890-50-2290-50-r?90-50-3090-50-8990-50-7990-50-8190-50-8090-52-2390-52-r290-50-9490-50-32Reel Table Screw(2)Reel Table (2)Pinch Wheel ScrewPinch Wheel-Models 90 & 90-SPinch Wheel-Model 90-CTransport Deck PanelRecord-Play KnobSet ScrewWind-Rewind KnobTransport Deck Panel, Head &ControlsTake-up Spring Post BrackelBracketWind-Take-up Slide Bar Spring-Models 90 & 90-SBracketRetaining RingTake-up Brake Link LeverTake-up Brake SpringTake*up Brake Bar LeverPause Lever-Model 90-CPause- Lever Load Spring-Model90-cWind-Rewind Operating CamSet ScrewSteel Ball.Ref.No.PartNo.Description2223242526272829303t32333435363?38394090-50-8690-50-9090-50-?890-50-8?90-50-2590-50-2490-50-3690-50-?290-50-9290-50-8290 -50-7?90-50-5r90-50-3990-50-9190-52-4390-50-93Rewind-Take-up Control PivotRollerTake-up Brake Link SpringMain-Brake Pivot Bar LeverWind-Take-up Control PivotLever-Models 90 & 90-SDeck Baseplate (State Model)Take-up SpindleSplined RollerRetaining RingWasherMain-Drive Idler WheelDrive Idler Load SpringWind-Take-up ldler Pivot BarLeverBrake Shoe, SmallMain-Drive Idler Pivot LeverScrewSpindle Mounting PlateRoller Securing ScrewDrive Idler Pivot Lever-Models 90 & 90-SDrive Idler Pivot Lever-Model 90-CRollerPlav-Record Operating CamPage 64l424344irs46474B49505I525354606l62636465666?6?A6B69?0?i72?374?5?617?8?9808i82B384.8586-1MECHAN ICAL PARTS LIST (CONT. )90-52-2190-52-0890-51-?90-5r-0690-50-5?90 -52-0490 -52-0?90-52-2690 -52-tI90-50-4890-5r-9690-5r-?390-51-1890-50-5590-3190-5r-6490-51-?290 -5I-9590-52-0590-52-1390-52-r090-50-4490-50-4590-50-6390-52-4690-50-0290-52-0690-52-4290-50-3690 -50-3990-50-6590-50-?790-50-?590-50-7690-50-0?90-50-3990-50-33Ch. 2 Shorting SwitchRewind Activating LeverRecord Lock ButtonRecord Lock SpringRecord Lock ScrewLockwasherInsulatorInsulatorRewind Idler WheelRewind Positioning LeverTape-Drive Idler Load SpringRewind Intermediary-Idler LoadSpringHead Cover ScrewHead Cover-Model 90-CHead Cover-Model 90-SHead Cover-Model 90Head ScrewMichigan Mag. Head Assy.,Stereo-Model 90-SHead Assy. , Monaural-Model 90Head Ass y., Stereo-Model 90-SMultierase Head Assy. ,Stereo-Model 90-CRetaining RingWasherRewind Intermediary-Idler WheeModel 90-CIntermediary-Idler Spring LeverScrewIntermediary-Idler Spring LeverRewind-Idler Release SpringTape -Guide BalI-Bearing ScrewTape-Guide Top PlateTape-Guide !trasherTape-Guide BaII BearingFeed-Reel Spindle Assy. -Model90-C Includes Items 6? thru 72Feed-Reel Spindle Assy. BeltRewind-Models 90 & 90-SRubber Rewind Drive Ring-Model 90-CConical Spindle SpringWasherRetaining RingSplined RollerWasherSpindle Housing ScrewSpindle Mounting PlateTake-up Spindle SpringWa