Califone-5275-tape-sm维修电路原理图.pdf

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1、RadioFans.CN 收音机爱 好者资料库Page 2SPECIFICATIONSPower output:Wow and Flutter:Audio Frequency Response:Signal to Noise Ratio:Mic Input:Aux Input:Aux Output:Sync Track Frequency Response:Sync Input/Output:Sync Tones:Fast Forward/Rewind Time:Speaker:Power Source:Dimensions:Weight:2 watts continuous (rms) in

2、to 9 ohms at less than 5% THD,Less than 0.22% wrms8Hz to 10kHz +/-3dB.45 dB minimum unweighted.0.25 mV sensitivity, for use with microphones withimpedance ratings between 50 and 5,000 ohms.250 mV sensitivity at 15,000 ohms impedance.500 mV from 0 dB reference tape, 250 nW/m.,I,000 ohms impedance80 H

3、z to 8,000Hz + / - 5 dB.500 mV rms referred to 250 nW/m. recorded level150 Hz Tape Stop/Restart, 1,000 Hz Slide advance.100 seconds for C-60 cassette.5” round.12OV 50-60 Hz AC (240V 50-60 Hz option available)or four D-size batteries.1 1” x 1 1” x 3 -1/2”.Approximately 6.0 Ibs.DESCRIPTION OF OPERATIO

4、NPOWER SUPPLYPower can be supplied to the 5275 either via line cord or bat-teries. The unit comes wired for 12OVAC but the wiring can bechanged to 230VAC. Contact the factory for details. Q10 is adiode-connected germanium transistor, used to keep AC-de-rived power from being fed into the batteries w

5、hile offering thelowest forward voltage drop from the battery supply. D21 pre-vents battery voltage from charging C97, eliminating the possibil-ity of capacitor leakage causing the battery to rundown.SW9 switches on the power whenever the tape transport is en-gaged. Thedifferent LEDs can be monitore

6、d by putting the trans-port into Play and Pause.AUDIO RECORD/PLAYBACKThe use of an integrated circuit designed specifically for cassettesystems considerably simplifies the circuitry necessary for re-cord and playback of audio signals in the 5275. This monolithicIC contains a preamplifier circuit, an

7、 automatic level control cir-cuit, a bridged power amplifier, and a meter drive circuit. Con-sequently, the external circuitry for the audio portion of the 5275consists mainly of switching, equalization, and coupling. The onlyactive devices are Q12 and Q13, which mute the main amp dur-ing turn-on wh

8、ile the preamp voltages come up and stabilize.Q14, an Aux Out buffer, and Q18, which locks the ALC circuit offin Audio Playback.For recording, the Bias Oscillator is turned on via SW1-5 by bias-ing Q2 to saturation. This provides aground to the emitter of Ql,which starts the Bias Oscillator.With no

9、external inputs connected to the unit, the Internal Micro-phone is automatically connected as a signal input in the RecordMode. Plugging in an Auxiliary Input disconnects the InternalMike; connecting an External Microphone disconnects either theInternal Mike or the Aux Input. The Internal Loudspeake

10、r is dis-connected in the Record Mode to eliminate acoustic feedback.The signal being recorded can be monitored via the ExternalSpeaker Jack by headphones or by a loudspeaker placed farenough from the signal source to prevent acoustic feedback.CAUTION: Always be sure the Red Cue (Sync) Rec/Erase lig

11、htis OFF when playing an audio-only tape with material recordedon both sides.When playing back prerecorded tapes, it is possible, under thefollowing circumstances, to erase the side of the tape you are notlistening to:1. Sync Rec/Erase On2.Erase Prevention Tab for other side is in place (affects hom

12、e-made tapes: commercial tapes come with this tab removed).The reason for this is that the Sync Track recorded by the 5275corresponds to the “other side” of a normal audio-only cassette.Thus if you take a cassette you have recorded and play it on the5275 with the Sync Record Switch on, you will eras

13、e the side youare not listening to unless me small plastic tab at the rear righthas been pushed out. If the tab has not been removed, SW8 willdose. allowing SW5 to turn on the Sync Record/Erase circuitry.Commercial tapes are not subject to this problem as they comewith no tab in place.SYNCTONERECORD

14、ANDPLAYBACKThe 5275 has circuitry for sensing and recording 150 Hz and 1kHz tones for making and using ANSI Standard synchronizedslide programs using one or two slide projectors or one slide pro-jector with a Sync (Cue) Tone to stop the cassette motor. The fol-lowing description primarily concerns i

15、tself with the 150 Hz sens-ing circuit; the 1 kHz circuit is identical in theory, differing only intime constants, except as noted.The heart of the circuit is a twin-T network in the feedback ofIC3D. This network has medium Q and makes the IC a sensitivefilter. When the Q issufficientlyincreased, th

16、e IC bewmes an os-cillator. The combination of R132 and R163 makes the networkhave only medium Q; when Q8 shunts R163, the circuit oscil-lates, generating a Sync Tone.RadioFans.CN 收音机爱 好者资料库Page 3SYNC PLAYBACK SECTIONLets follow doesa prerecorded Sync Tone of 150 Hz through the unit,noting the diffe

17、rence between what a 150 Hz and a 1 kHz toneIn the Playback Mode, RL-3 is off, leaving the Sync Track Eraseand Record/Playback Heads connected as shown in theschematic. The signal comes off the head and is mixed with 2.3VDC from voltage divider RlO7, R108, R111 This DC voltagebiases IC2A for midpoin

18、t operation. The signal is amplified andequalized by IC2A, further amplified by Q15, and goes throughSW4-1 and the Sync Out Jack. The 2.3V DC level is present atthe output of IC2A, and is fed through R128 to the emitter of Q4and through R141 to the base of Q5. SW4-1 is set to either TapeStop or Proj

19、 2 for Sync use; the center CM position is used whenplaying a standard audio tape so that a 150 Hz audio tone on thecassette will not command a Motor Stop. When an output istaken from the Sync Out Jack, the Sync Tone does not proceedthrough the 5275, ensuring that a Motor Stop command can notstop th

20、e motor when a program tape is being copied.VR3 adjusts the level of the Sync signal going into the ToneSense and Projector/Motor Control circuits. The signal is fed tothe non-inverting input of IC3D, which is biased by RI20 andRl35. The twin-T network feeds back to IC3D all but the SyncTone. causin

21、g the Sync Tone to be greatly amplified. Q16 is onduring normal playback, so the signal proceeds to a rectifier andfilter circuit which turns on IC2D, a comparator with hysteresisset to trigger with any input greater than one signal diode drop(approx. 0.2V DC). At this point several things can happe

22、n in the150 Hz circuit; in the 1 kHz circuit, Cl3 turns on RL-1, advancingProjector 1 one frame.In the 150 Hz circuit. Q6 is turned on when IC2D comes high. If ”SW4 IS in the Proj 2 position, this turns on RL1, advancing Pro-jector 2 by one frame. If SW4 is in the Tape Stop position, Q6brings the em

23、itter of Q5 low in comparison with the 2.3V DC de-rived from lC2A, turning on Q5. The charge on C96 (at the motor)is then shunted to ground through RI 64, Q5, SW4, and Q6, turn-ing off Q1 , and the motor stops. As the charge on C67 drops tozero volts, C102 discharges and Q16 turns off. Current flows

24、through Q4 to the base of Q6, keeping the motor off until SW7,the Tape Stop/Restart Switch, is activated.When SW7 is activated, 5V DC is fed through D6 to the base ofQ4. D25, connected from RI74 and C63 to the motor (which isnow off and effectively at ground), shunts this voltage away fromthe 150 Hz

25、 generating circuit described in the Sync Record sec-tion below, thus keeping the motor from being turned off againduring the restart process. Bringing up the base of Q4 turns it off,turning off Q6, turning off Q5, allowing C96 to charge, turning onQ11 and the cassette motor. Q1 6 is already turned

26、off, so any re-maining Sync Tone on the tape can not restop the motor. Thecollector voltage of Q6 is pulled up by R R144and Tape Stop LED0 D18.C C102 on Q16 i isis meanwhile slowly charging; about onesec-ond is necessary to charge this capacitor and enable the circuitto tum the motor off again.In th

27、e Playback Mode, any external Sync In is shunted to groundthrough Rl45, bias trap C73 and L4, and RL-3. The Sync OutJack disconnects the sync signal from the Sync Tone Sense cir-cuitry whenever a connector is plugged into the SyncOut Jack sothat a Motor Stop command on the tape will not stop the mot

28、orwhile a tape is being copied.During Audio Record, a large amount of Bias frequency signal isinduced in the Sync Playback head; Q17 shunts this to ground inthe Audio Record Mode to keep the electronics from being over-whelmed by this unwanted Bias signal.SYNC RECORD SECTIONSW5 and SW6 enable the Sy

29、nc (Cue) Tone Erase/Record cir-cuitry when they are closed, biasing IC2B for midpoint operation,turning on RL-3 and Dl6, and biasing Q2 into saturation, whichstarts the Bias Oscillator by providing a ground for the emitter ofQ1. (For audio recording, the biasoscillator is turned on by SW1-5 whether

30、Sync Record is on or off.) SW6 is located in the tapetransport, behind the right side of the cassette. It closes when theErase Prevention Tab of the cassette is in place. (See the Cau-tion in the Audio Playback section regarding accidental erasureof prerecorded tapes.) SW5 is the front panel Sync Re

31、cordSwitch.When SW5 and SW6 are both closed and the transport is en-gaged. Sync Tones are recorded on the cassette wheneverSW6, Slide Advance (Proj I), or SW7, Tape Stop/Restart (or Proi2), is closed. Sync tones are audible through the loudspeakerduring the Sync Record due to magnetic coupling betwe

32、en thetwo halves of the Record/Playback Head.Lets follow the signals through the record circuitry of the 150 Hzsection, noting the differences between the 150 Hz and 1 kHzsections. The 150 Hz section is chosen for this example as it isthe more complicated circuit.When RL-3 closes, its terminals 9 an

33、d 15 shunt to ground the 2.3V DC bias on the non-inverting input of IC2A. This brings the DClevel of IC2As output to ground, removing this voltage from theemitter of Q4 and the base of Q5. As a result, the Sync Tonesgenerated by the 150 Hz oscillator can not turn off the motor inthe Sync Record Mode

34、.When the unit is in Audio Record, magnetic coupling betweenthe two halves of the Record Head induces a very low current 60kHz Bias voltage into the input of IC2A. Q17 shorts any resultantoutput to ground so that it can not be fed into the tone sense cir-cuitry.Momentary closure of Tape Stop/Restart

35、 Switch SW7 (or short-ing pins 3 and 5 of the Remote Plug via a remote control unit) ap-plies 5V DC to R174 and D8. C63 makes this into a pulse whichis fed through D15 and R171 into IC3C, a one-shot with about a0.5 second on-time. The positive output from IC3C turns on Q8,shorting R163 and greatly i

36、ncreasing the Q of the twin-T network.turning IC3D into an oscillator. The output of IC3D goes into IC2Bthrough a mixing network and level set rheostat VR4. The outputof IC2B is fed through the Sync In Jack. If no plug is in this jack,the signal proceeds through bias trap C73, L4 directly to the re-

37、cord head. Record bias is fed to the Record head through C51andRll4.The outputs of IC3D and IC3A are also fed into their respectiverectifier networks and IC2D. It is therefore normal for Projector 1relay RL-1 to close whenever a 1 kHz Sync Tone is recorded onthe tape. If SW4 is in the Proj 2 positio

38、n, RL-2 will close whenevera 150 Hz tone is recorded on the tape.When an external Sync source is used, Sync In Jack J7 preventsany internally generated tones from reaching the Record Head.External Sync In senstivity is nominally 500mV. Connecting aplug to Sync Out Jack J6 prevents Sync Tones recorde

39、d on thetape from reaching the sensing circuitry. Sync Out signals arealso nominally 5OOmV.Page 6TROUBLESHOOTING THE 5275TROUBLESHOOTING SECTIONSThe Troubleshooting Information on the following pages has been dividedinto three sections with subsections in order to make it easier for the techni-cian

40、to find the particular section of interest. It is recommended that the fol-lowing outline be used for troubleshooting:1.2.3.4.Try out the unit, preferably with the customers tape, until the malfunc-tion occurs.If the motor works, skip Section I, Power Supply, and go directly to therelevant section.N

41、ote that the subsections are in functional order; for instance troub-leshooting a problem with Audio Record means that Audio Playbackmust first be verified.The Sections are as follows:I. Power Supply and Motor IIA. Audio Playback IIIA. Sync Tone GeneratorIIB. Audio Record 111B. Sync RecordIIIC. Sync

42、 PlaybackIIID. Sync and Audio RecordDirections: Follow each test in order. The correct voltage or terminal, which is located on the left side of the unit and has awaveform will lead you to the next step; an in correct rneasure- black wire connected to It.ment will lead you to the defective component

43、(s). From Step All voltages given are nominal, and may be 10% above or2 on, the ground connectiin is taken from the negative battery below the stated voltages.1. POWER SUPPLY AND MOTORPage 7IIMost of the following tests are concerned with components to outside circuitry, so improper voltages on thes

44、e pins, if ex-connected to ICl. If, at any point, there is a performance ternal pads are good. suggest replacement of the IC:PINS 2,problem and all external components check good, recheck 3,4,6,8,13,17.18,19,20.the DC voltages on IC1 The following pins are all AC coupledIIA. AUDIO PLAYBACKIIB AUDIO

45、RECORDPage 8Review the Sync Tone Record and Playback section of the After Step 1, the following text deals directly with the 150 HzGeneral Description; your troubleshooting will be facilitated section. Component designations for the 1 kHz section are inby understanding the description of operation g

46、iven there. parenthesis where the two sections have common parts.IIIA. SYNC TONE GENERATORSPage 9Page 10ISWITCH DESIGNATIONS TRANSISTOR FUNCTIONSQ 1 Bias OscillatorQ 2 Bias Oscillator EnableQ 3 Projector 1 Relay DriveQ 4 Motor Restart0 5 Motor Stop ControlQ 6Projector 2 Relay Drive, Motor StopQ 7 1

47、kHz Oscillator StartQ 8 150 Hz Oscillator StartQ 9 5.OV DC RegulationQ10 Battery DiodeQ11 Motor Supply Regulation/ShutoffQ12Power-up Audio Mute CircuitQ13Power-up Audio Mute CircuitQ14 Aux Out BufferQ15 Sync PlaybackQ16Motor Restart Tone InterruptQ17 Sync Out ShuntQ18 Playback ALC DefeatSW FunctionS

48、W1 REC/PLAY, shown in PlaySW2 PASW3 ALCSW4 Tape Stop/Off/Proj. 2SW5 Sync Record/EraseSW6 Slide (1) AdvanceSW7 Tape Stop/Restart,Slide (2) AdvanceSW8 Anti-Sync RecordSW9 Main PowerLocationMain PC BoardFront PanelFront PanelJack PanelFront PanelFront PanelFront PanelTransport, right rearTransportINTEG

49、RATED CIRCUIT FUNCTIONSICl TA7224P Preamp, ALC, Main Amp,Meter DriveIC2 TA75324P A:Sync Playback/EQB:Sync Oscillator Outc:Proj 1 Drive ComparatorD:Proj 2 Drive Comparator1 kHz Filter/Oscillator1 kHz Oscillator Start150 Hz Oscillator Start150 Hz Filter/OscillatorIRELAY FUNCTIONSIRL 1 Projector 1 AdvanceRL 2 Projector 2 AdvanceRL 3 Sync RecordIC3 TA75324P A:B:c:D:I IBAllmYBLOCK DIAGRAM5275