Califone-5275-tape-sm 电路图 维修手册.pdf

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1、RadioFans.CN 收音机爱 好者资料库 Page 2 SPECIFICATIONS Power 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 c

2、ontinuous (rms) into 9 ohms at less than 5% THD, Less than 0.22% wrms 8Hz to 10kHz +/-3dB. 45 dB minimum unweighted. 0.25 mV sensitivity, for use with microphones with impedance 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.

3、, I,000 ohms impedance 80 Hz to 8,000Hz + / - 5 dB. 500 mV rms referred to 250 nW/m. recorded level 150 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”. Approximat

4、ely 6.0 Ibs. DESCRIPTION OF OPERATION POWER SUPPLY Power can be supplied to the 5275 either via line cord or bat- teries. The unit comes wired for 12OVAC but the wiring can be changed to 230VAC. Contact the factory for details. Q10 is a diode-connected germanium transistor, used to keep AC-de- rived

5、 power from being fed into the batteries while offering the lowest 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

6、is en- gaged. Thedifferent LEDs can be monitored by putting the trans- port into Play and Pause. AUDIO RECORD/PLAYBACK The use of an integrated circuit designed specifically for cassette systems considerably simplifies the circuitry necessary for re- cord and playback of audio signals in the 5275. T

7、his monolithic IC contains a preamplifier circuit, an 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 5275 consists mainly of switching, equalization, and coupling. The only active devices ar

8、e Q12 and Q13, which mute the main amp dur- ing turn-on while the preamp voltages come up and stabilize. Q14, an Aux Out buffer, and Q18, which locks the ALC circuit off in Audio Playback. For recording, the Bias Oscillator is turned on via SW1-5 by bias- ing Q2 to saturation. This provides aground

9、to the emitter of Ql, which starts the Bias Oscillator. With no external inputs connected to the unit, the Internal Micro- phone is automatically connected as a signal input in the Record Mode. Plugging in an Auxiliary Input disconnects the Internal Mike; connecting an External Microphone disconnect

10、s either the Internal Mike or the Aux Input. The Internal Loudspeaker is dis- connected in the Record Mode to eliminate acoustic feedback. The signal being recorded can be monitored via the External Speaker Jack by headphones or by a loudspeaker placed far enough from the signal source to prevent ac

11、oustic feedback. CAUTION: Always be sure the Red Cue (Sync) Rec/Erase light is OFF when playing an audio-only tape with material recorded on both sides. When playing back prerecorded tapes, it is possible, under the following circumstances, to erase the side of the tape you are not listening to: 1.

12、Sync Rec/Erase On 2.Erase Prevention Tab for other side is in place (affects home- made tapes: commercial tapes come with this tab removed). The reason for this is that the Sync Track recorded by the 5275 corresponds to the “other side” of a normal audio-only cassette. Thus if you take a cassette yo

13、u have recorded and play it on the 5275 with the Sync Record Switch on, you will erase the side you are not listening to unless me small plastic tab at the rear right has been pushed out. If the tab has not been removed, SW8 will dose. allowing SW5 to turn on the Sync Record/Erase circuitry. Commerc

14、ial tapes are not subject to this problem as they come with no tab in place. SYNCTONERECORDANDPLAYBACK The 5275 has circuitry for sensing and recording 150 Hz and 1 kHz tones for making and using ANSI Standard synchronized slide programs using one or two slide projectors or one slide pro- jector wit

15、h a Sync (Cue) Tone to stop the cassette motor. The fol- lowing description primarily concerns itself with the 150 Hz sens- ing circuit; the 1 kHz circuit is identical in theory, differing only in time constants, except as noted. The heart of the circuit is a twin-T network in the feedback of IC3D.

16、This network has medium Q and makes the IC a sensitive filter. When the Q issufficientlyincreased, the IC bewmes an os- cillator. The combination of R132 and R163 makes the network have 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

17、 3 SYNC PLAYBACK SECTION Lets follow does a prerecorded Sync Tone of 150 Hz through the unit, noting the difference between what a 150 Hz and a 1 kHz tone In the Playback Mode, RL-3 is off, leaving the Sync Track Erase and Record/Playback Heads connected as shown in the schematic. The signal comes o

18、ff the head and is mixed with 2.3V DC from voltage divider RlO7, R108, R111 This DC voltage biases IC2A for midpoint operation. The signal is amplified and equalized by IC2A, further amplified by Q15, and goes through SW4-1 and the Sync Out Jack. The 2.3V DC level is present at the output of IC2A, a

19、nd is fed through R128 to the emitter of Q4 and through R141 to the base of Q5. SW4-1 is set to either Tape Stop or Proj 2 for Sync use; the center CM position is used when playing a standard audio tape so that a 150 Hz audio tone on the cassette will not command a Motor Stop. When an output is take

20、n from the Sync Out Jack, the Sync Tone does not proceed through the 5275, ensuring that a Motor Stop command can not stop the motor when a program tape is being copied. VR3 adjusts the level of the Sync signal going into the Tone Sense and Projector/Motor Control circuits. The signal is fed to the

21、non-inverting input of IC3D, which is biased by RI20 and Rl35. The twin-T network feeds back to IC3D all but the Sync Tone. causing the Sync Tone to be greatly amplified. Q16 is on during normal playback, so the signal proceeds to a rectifier and filter circuit which turns on IC2D, a comparator with

22、 hysteresis set to trigger with any input greater than one signal diode drop (approx. 0.2V DC). At this point several things can happen in the 150 Hz circuit; in the 1 kHz circuit, Cl3 turns on RL-1, advancing Projector 1 one frame. In the 150 Hz circuit. Q6 is turned on when IC2D comes high. If ” S

23、W4 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, Q6 brings the emitter 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,

24、 SW4, and Q6, turn- ing off Q1 , and the motor stops. As the charge on C67 drops to zero volts, C102 discharges and Q16 turns off. Current flows 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 t

25、o the base of Q4. D25, connected from RI74 and C63 to the motor (which is now off and effectively at ground), shunts this voltage away from the 150 Hz generating circuit described in the Sync Record sec- tion below, thus keeping the motor from being turned off again during the restart process. Bring

26、ing up the base of Q4 turns it off, turning off Q6, turning off Q5, allowing C96 to charge, turning on Q11 and the cassette motor. Q1 6 is already turned off, so any re- maining Sync Tone on the tape can not restop the motor. The collector voltage of Q6 is pulled up by R R144and Tape Stop LED 0 D18.

27、C C102 on Q16 i isis meanwhile slowly charging; about onesec- ond is necessary to charge this capacitor and enable the circuit to tum the motor off again. In the Playback Mode, any external Sync In is shunted to ground through Rl45, bias trap C73 and L4, and RL-3. The Sync Out Jack disconnects the s

28、ync signal from the Sync Tone Sense cir- cuitry whenever a connector is plugged into the SyncOut Jack so that a Motor Stop command on the tape will not stop the motor while a tape is being copied. During Audio Record, a large amount of Bias frequency signal is induced in the Sync Playback head; Q17

29、shunts this to ground in the Audio Record Mode to keep the electronics from being over- whelmed by this unwanted Bias signal. SYNC RECORD SECTION SW5 and SW6 enable the Sync (Cue) Tone Erase/Record cir- cuitry when they are closed, biasing IC2B for midpoint operation, turning on RL-3 and Dl6, and bi

30、asing Q2 into saturation, which starts the Bias Oscillator by providing a ground for the emitter of Q1. (For audio recording, the biasoscillator is turned on by SW1- 5 whether Sync Record is on or off.) SW6 is located in the tape transport, behind the right side of the cassette. It closes when the E

31、rase Prevention Tab of the cassette is in place. (See the Cau- tion in the Audio Playback section regarding accidental erasure of prerecorded tapes.) SW5 is the front panel Sync Record Switch. When SW5 and SW6 are both closed and the transport is en- gaged. Sync Tones are recorded on the cassette wh

32、enever SW6, Slide Advance (Proj I), or SW7, Tape Stop/Restart (or Proi 2), is closed. Sync tones are audible through the loudspeaker during the Sync Record due to magnetic coupling between the two halves of the Record/Playback Head. Lets follow the signals through the record circuitry of the 150 Hz

33、section, noting the differences between the 150 Hz and 1 kHz sections. The 150 Hz section is chosen for this example as it is the more complicated circuit. When RL-3 closes, its terminals 9 and 15 shunt to ground the 2.3 V DC bias on the non-inverting input of IC2A. This brings the DC level of IC2As

34、 output to ground, removing this voltage from the emitter of Q4 and the base of Q5. As a result, the Sync Tones generated by the 150 Hz oscillator can not turn off the motor in the Sync Record Mode. When the unit is in Audio Record, magnetic coupling between the two halves of the Record Head induces

35、 a very low current 60 kHz Bias voltage into the input of IC2A. Q17 shorts any resultant output to ground so that it can not be fed into the tone sense cir- cuitry. Momentary closure of Tape Stop/Restart Switch SW7 (or short- ing pins 3 and 5 of the Remote Plug via a remote control unit) ap- plies 5

36、V DC to R174 and D8. C63 makes this into a pulse which is fed through D15 and R171 into IC3C, a one-shot with about a 0.5 second on-time. The positive output from IC3C turns on Q8, shorting R163 and greatly increasing the Q of the twin-T network. turning IC3D into an oscillator. The output of IC3D g

37、oes into IC2B through a mixing network and level set rheostat VR4. The output of 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- cord head. Record bias is fed to the Record head through C51 andRll4. The outputs of IC

38、3D and IC3A are also fed into their respective rectifier networks and IC2D. It is therefore normal for Projector 1 relay RL-1 to close whenever a 1 kHz Sync Tone is recorded on the tape. If SW4 is in the Proj 2 position, RL-2 will close whenever a 150 Hz tone is recorded on the tape. When an externa

39、l Sync source is used, Sync In Jack J7 prevents any internally generated tones from reaching the Record Head. External Sync In senstivity is nominally 500mV. Connecting a plug to Sync Out Jack J6 prevents Sync Tones recorded on the tape from reaching the sensing circuitry. Sync Out signals are also

40、nominally 5OOmV. RadioFans.CN 收音机爱 好者资料库 Page 6 TROUBLESHOOTING THE 5275 TROUBLESHOOTING SECTIONS The Troubleshooting Information on the following pages has been divided into three sections with subsections in order to make it easier for the techni- cian to find the particular section of interest. I

41、t 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 the relevant section. Note that the subsections are in fun

42、ctional order; for instance troub- leshooting a problem with Audio Record means that Audio Playback must first be verified. The Sections are as follows: I. Power Supply and Motor IIA. Audio Playback IIIA. Sync Tone Generator IIB. Audio Record 111B. Sync Record IIIC. Sync Playback IIID. Sync and Audi

43、o Record Directions: Follow each test in order. The correct voltage or terminal, which is located on the left side of the unit and has a waveform will lead you to the next step; an in correct rneasure- black wire connected to It. ment will lead you to the defective component(s). From Step All voltag

44、es given are nominal, and may be 10% above or 2 on, the ground connectiin is taken from the negative battery below the stated voltages. 1. POWER SUPPLY AND MOTOR Page 7 II Most of the following tests are concerned with components to outside circuitry, so improper voltages on these pins, if ex- conne

45、cted 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 coupled IIA. AUDIO PLAYBACK IIB AUDIO RECORD Page 8 R

46、eview the Sync Tone Record and Playback section of the After Step 1, the following text deals directly with the 150 Hz General Description; your troubleshooting will be facilitated section. Component designations for the 1 kHz section are in by understanding the description of operation given there.

47、 parenthesis where the two sections have common parts. IIIA. SYNC TONE GENERATORS Page 9 Page 10 I SWITCH DESIGNATIONS TRANSISTOR FUNCTIONS Q 1 Bias Oscillator Q 2 Bias Oscillator Enable Q 3 Projector 1 Relay Drive Q 4 Motor Restart 0 5 Motor Stop Control Q 6Projector 2 Relay Drive, Motor Stop Q 7 1

48、 kHz Oscillator Start Q 8 150 Hz Oscillator Start Q 9 5.OV DC Regulation Q10 Battery Diode Q11 Motor Supply Regulation/Shutoff Q12Power-up Audio Mute Circuit Q13Power-up Audio Mute Circuit Q14 Aux Out Buffer Q15 Sync Playback Q16Motor Restart Tone Interrupt Q17 Sync Out Shunt Q18 Playback ALC Defeat

49、 SW Function SW1 REC/PLAY, shown in Play SW2 PA SW3 ALC SW4 Tape Stop/Off/Proj. 2 SW5 Sync Record/Erase SW6 Slide (1) Advance SW7 Tape Stop/Restart, Slide (2) Advance SW8 Anti-Sync Record SW9 Main Power Location Main PC Board Front Panel Front Panel Jack Panel Front Panel Front Panel Front Panel Transport, right rear Transport INTEGRATED CIRCUIT FUNCTIONS ICl TA7224P Preamp, ALC, Main Amp, Meter Drive IC2 TA75324P A:Sync Playback/EQ B:Sync Oscillator Out c:Proj 1 Drive Comparator D:Proj 2 Drive Comparator 1 kHz Filter/Oscillator 1 kHz Oscillator Start 150 Hz Oscillator Start 150 Hz