tandberg 12-servicemanual 维修电路原理图.PDF

,*;y T).oW,*q r=-r=f-rr5r/ Service manual MNDBERG Tape recorder modell 12 Preface This service manual covers the Tandberg tape recor- der models l2-4 and 12-2.fhe model series l2 is a fully transistorised, three speed stereo, record arrd playback unit with two heads. lt is equipped with separate record and playback preamplif iers and sepa- rate power amplifiers for each channel. The power output amplifiers are rated for l0 watts each. The model 12 -2 is the two-track version while the model I 2-4 is the four-track version. The models 12-2 and )2-4 have exaclly the same mechanical system and operating controls. We hope thot everyone concerned with our products will find this service manual useful. April 1967 1 1 Tr Contents Technicol specificqlion, Tondberg tope recorder models l2-4 ond l2-2 . The function of the conlrols The inpuf ond outpuf lerminols The mechonism, detoiled descripiion ond odiusiment instruciion The operoling lever . . 4.I.1 The moior switch 1.1.2 lhe eccentric segment 4.1.3 The pressure wheel ossembly 4.1.4 The tope broke 4.1.5 The trip bor 4.2 The turnfoble ossemblies 4.2.1 lhe supply turnfoble ossembly r 4.2.2 lhe lope iight lension . 4.2.3 The toke-up turntoble ossembly A.2.4 Horizontsl ond veriicql olignments of the furntobles 1.3 Clulch olignments 4.3.1 Generol 4.3.2 Fost rewind 4.3.3 Fost wind 4.3.4 Normql forword drive . . 4.3.5 Neutrol 4.3.6 Free 4.4 fhe motor pulley 4.4.1 Threoding of the rubber drive belt 4.5 The speed lronsfer wheel 4 . 6 T h e l i f t i n g m e c h o n i s m . . . . . . . . . . . . 1 9 5.2.1 The f unclion selecior swilch 5.2.2 lhe speoker selector swilch . 5.2.3 Monourol recording on CHI or CH2 , . 5.2.4 Mixing during monourol recording 5.2.5 Stereo recording 5.2.5 Monourol ploybock, chonnel I or 2 . .,. 5.2.7 Stereo ploybock 33 5.2.8 Stereo omplifier 33 5.2.9 Add o irock . 33 S.2,l0Sound on sound 34 5.3 Heod olignment ond frock conlrol with Tondberg test tope 34 5.3.I The Models l2-4 and 12-2 . 34 5.3.2 The model l2-2 35 1.0 3t 3l 32 32 33 a? 33 32 35 a 5 35 35 5.5 5.6 35 36 36 36 36 35 36 2.O 3.0 4.O 1.1 e 9 9 t0 l 0 1 2 t 2 t 2 I J l 3 t 4 l 5 15 t5 l 6 l 6 1 7 t 7 l 8 t8 l 8 l 8 JJ JJ A E ) 4.9 The momenlqry stort-stop feoture 4.10 The pressure pqd . . . 4.l l The oulomotic end sfop switch . 4.12 The revolulion counler . 4.13 Assembling the fop cover 5.0 The electronic circuits, detoiled descriplion ond odiusfmenl instruction 5.1.1 lnpuls 5,I .2 The record pre-omplif ier 5.1.3 The FM multiplex-filter 5.1.4 The equolizing omplifier in record posiiion . . 25 5.1.5 The equolizing omplifier in ploybock position . . . 26 5.1.6 The equolizing omplifier in omplifier posilion . . . 27 5.1,7 lhe power oulput omplifier 28 5.1.8 The ploybock pre-omplifier 29 5.1.9 The record level indicotor circuit . 29 5,l.l0The oscillotor, bios ond erose circuit 29 5.l,ll The power supply 30 5.4 Heod olignment without Tqndberg test topes 5.4.1 Demognetizing 5.4.2 The odlustoble tope guides 5.4.3 The record/ploybock heod 5.4.4 The erose heod Trock conlrol, model l2-4 without Tqndberg test lqPes . - 5.5,1 The record/ploybock heod 5.5.2 The erose heqd Trock conlrol, model l2-2 without Tondberg lesi topes . 5.6.1 The erose heod 5.6.2 The record/ploybock heod . . Electrical qdiustments for Tondberg tope recorder models 12-4 ond 12-2 . . 5.7.1 Adiustment of ihe Power outPuf omplifier 5.7.2 Adiusfment of the outpui level 5.7.3 The quiescent currenl . 5.7.4 Adiustment of the FM MX-filter 5.7.5 Control of lhe frequency response in omp position 5.7.6 The boss conlrol 5.7.7 The ireble control 5.7.8 ,Adiusfment of the record currenf ond the eleclronic beqm indicotor circuits . The electronic beqm indicolors The record current. Adivstment of the osc, frequency ond the bios . Dislortion Bolonce odiustment of lhe pre-omP ouiPuts Adiusiment of the equolizoiion coils Ll ond L2 . Control of the recording curves . Control of the ploybock curves . Control of the lotol frequency resPonse Power oulpul control . Speed test 36 36 5.7 1.7 1.9 The flywheel with ihe copston 4.7,1 The broke for the flywheel The speed chonge mechonism . . . 20 21 ) O 2l 22 22 22 22 24 24 25 25 36 1A 37 38 2 a J d 39 39 39 5.7.9 5.7. r 0 5.7 .t I 5.7.12 5.7.13 5.7.1 4 5.7.15 5.7.16 5.7.17 5.7.18 5.7.19 l ,1 i .t t t T t tI tt 5.8 Electricol modificotions introduced to the tope recorder m o d e l 1 2 . . . . . . . . 4 0 5,9 Modificolions from four-trock to iwo-frock models . . . . . . 41 5.10 Modificofions from 220 volts 50 c/s to ll0 volfs 60 c/s . 4l 6 . 0 P o r t s l i s t . . . . . . . 4 l 6.0.1 Mechonicol ports 4l 6.0.2 Elecrricol ports . 46 1.0 Technical specification, Tandberg tape recorder models 12-4 and122 Power requirements: 220 volts 50 c/s. Power consumption: 58 watts at 2 X 1 ,25 watts output power. i 00 watts aI 2 X .l 0 watts output power. Motor: Four pole. Tapespeed: 71/2,33/t and l7/e inches per second. The amplifiers are equalized to conform with NAB standards. Playing time: Four-track recordings on 1200 ft. of tape: Model l2-4 Tape speed 7Vz i.p.s.: Stereo 2 X 32 min. Mono 4 X 32 min Tapespeed 37+ i.p.s.: Stereo 2X 64 min. Mono 4X 64min. Tape speed l7/o i.p.s. Stereo 2x 128 min. Mono 4 X i 28 min. Model l2-4: Two-track recordings on 1200 ft. of tape: Tape speed 7t/z i.p.s.: Stereo 32 min. Mono 2 X 32 min. A Tape speed 3% i.p.s.: Stereo 64 min. Mono 2 X 64 min. Tape speed 17/6 i.p.s.: Stereo .l28 min. Mono 2 X .I28 min. Fast wind and rewind: The fast wind or rewind of .l200 ft. of tape takes approx. 2 minutes. Tape path: The tape moves from left to right. The heads are positioned with the air gaps pointing towards the f ront of the tape recorder. Recording tape: Maximum reel diameter 7. Good quality recording tape is recommended. Automatic slop: The auiomatic stop operaies during record or playback as well as during fast wind or rewind modes. Heads: Model l2-4: Quarter-track erase head. Quarter-track combined record and playback head. Air gap: .003 mm (.O012). Model I2-2: Half-track erase heao. Half-track combined record and playback head. Air gap: .003 mm (.00012). Frequency response: 7 l, i.p.s. 30-20.000 c/s (l 2 dB 40- 16.000 c/s). 33/a i.p.s. 30- I 3.000 cls (-r 2 dB 50- I 0.000 c/s). 17/a i.p.s. 30- 2.000 c/s (+2 dB 60- 5.000 c/s). ln AMPLIFIER oosition: t 2 dB 30-.l6.000 c/s. Distortion: The distortion from the record amplifiers is less than .5 %. The distortion from the playback amplifiers is less than .5 %. i Signal to noise ratio Model l2-4: The signal to noise ratio is better than 55 dB when the tape is recorded to optimum recording level, i.e. nearly closing of the electronic beam indicator (5% disloriion from the tape). Model 12-2 The signal io noise ratio is better ihan 58 dB when the tape is recorded to optimum recording level, i.e. nearly closing of the electronic beam indicator (5 % distortion from the tape). Crosstalk: The crosstalk reiection is better than 60 dB at 400 c/s. Wow and f lulter: Better ihan .I % at 7t/z i.p.s. tape speed. I Better than .15 % at 33/+ i.p.s. tape speed. Belter than .25 Y al l/o i.p.s. tape speed. Erase and bias frequency: The erase and bias frequency is 85,5 kcls. The even harmonic distortion in the bias current is less than .5 %. Recording level indicaior The electronic beam indicators are equipped with damping circuits. The indicator range is 25 dB, plus overload. The indicators are closing at optimum recording level (5 % distortion from the tape). lnputs: 2 Microphone inpu?s (ch. I and ch,2l: lmpedance,200 ohms unbalanced. Sensitivity: l50pV. Dynamic range *40d8. Contacts: 5 pin DIN contacts. 4 Oulputs: Spea kers, Bass control: Treble control: Momentary start/stop tever: Counter: Tubes models l2-4 and l2-2: Tra nsi stors: Rectif iers: Dimensions: Weight: 2 line inputs (ch. I and ch. 2): HIGH LEVEL: Impedance: I Mohm. Sensitivity: 75 contacts and DIN connector marked LOW LEVEL: mV. Dynamic range +40 dB. Contacts: Phono CR PHONO (pin No. 3 and 5). lmpedance: .l00 kohms. Sensitivity: 7,5 mV. Dynamic range *40 dB. Contacts: Phono contacts and DIN connector marked RADIO (pin No. I and 4). FM-Multiplex inpuls: The model l2 tape recorder is furnished with a FM-Multiplex switch which switches the multiplex filter in or oui. The switch controls all inputs. Playback Preamplifier oulpul: lnternal impedance is 5 kohms. Open circuit output voltage 750 mV, independent of the setting of all switches and controls during playback. Two phono contacts (ch. I and ch.2) are furnished for connection to external power amplifiers. low lmpedance oulpul: External impedance is 4 ohms. Two standard telephone iacks (ch. I and ch. 2) in parallel with two DIN loudspeaker contacts are furnished for connection to external loudspeakers. Cenler Channel oulpul: lmpedance is 82 ohms from each amplifier. Output voltage in record posi- tion is 75O mY open circuit. Output voltage in playback position and amplifier position (AMP) is maximum 3 volts open circuit. One standard telephone iack in parallel with one DIN loudspeaker contact are furnished for connection to head- pnones. Power ouipul: Maximum output power is I0 watts in each channel. Two standard telephone iacks (ch. I and ch.2) in parallel with two DIN loudspeaker contacts are furnished for connection to external speakers. Two speakers 7 X 4. The bass response can be continuously increased approx. l2db at 80 c/s during playback or in amplifier mode. This increase of the low frequency amplification will only be presented on fhe channel which is set for playback or amplification even when the other channel is connected for recording. The treble response can be continuously decreased approx. 1 5 dB at I 5 kc/s during playback or in amplifier mode. Minimum bass and maximum treble correspond to f lat f requency response. The momeniary start/stop lever starts or stops the recording or playback instantly. The 4 digit counter shows the number of revolutions of the take-up turntable. 2 EAM 86. 2 pairs of complementary lransistors AC 127, AC 128 (alternatively AC 127, AC r52). 2 pairs of matched transistors AD 150 (alternatively AD 149 or STF 213). l0ea BC 1098, 2 ea BC 114, 6 ea BC 113, 2 ea BC 1078, 2 ea SE6002, i ea Tl 3030, 4 ea 284812. Bridge rectifiers: I ea B 40 C 3200. I ea B 250 C 75/30 KP. In teak cabinet l5 I u long, I l f ,u wide and 67/u high. Approx. 23 lbs. 2.0 The function of the controls l. Treble control: 2. Bass control: 3. Volume controls: 4. Record level ind icators: 7. Microphone inputs: Front and rear trim covers: Momentary start/ stop lever: Function selector switch, channel l: ,+1 Fig. l. The operoling conlrols. Decreases the treble continuously. Maximum treble decrease is approx. l5 dB at l5 kcis. The treble control is operative during playback and in AMP position. lncreases the bass continuously. Maximum bass increase is approi. l2 dB at 80 c/s. The bass conirol is operative during playback and in AMP position. Conirols the recording gain in record mode and the output volume in playback mooe. Upper knob: Channel 1 (Upper track). Lower knob: Channel 2 (Lower track). lndicates the recording level. Optimum recording level is obtained when the electronic beam indicators are nearly closed. Left indicator: Channel i (upper track). Right indicator: Channel 2 (lower track). Low impedance inputs (200 ohms) channel I and channel 2. Remove the trim covers to clean or demaqnetize the heads. Stops the recording or playback instantly when the lever is moved to the right position. The record or playback will start immediately when the lever is moved to left posiiion. 4, 6. 8. Activates the electronic circuits for record, playback or amplifier mode, channel l. 9. Funclion seleclor switch channel 2: l0. Automatic end stop switch: I l. Speaker selector switch. 12. Tape counter: 13. Operating lever: 14. Re-set push button: ; 15. Power switch: I 6. Speed selector: Activates the electronic circuits for record, playback or amplifier mode, channel 2. Stops the motor when the tape runs out or if the tape breaks. EXT: External speakers only. EXT* INT: External and internal speakers. INT: Internal speakers only. CHI EXT, CH2 INT: The output from CHI is connected to both external speaker terminals. The output from CH2 is connected to both internal speakers. CH2 EXT, CHI INT: The output from CH2 is connected to both external speaker terminals. The output from CHI is connected to both internal speakers. Indicates the position of the tape. Activates the mechanism in the lape recorder for the different modes of operalion. Re-sets the tape counter fo zero. Switches the mains on or off . Selects the required tape speed. 3.0 The input and output terminals The input and outpul terminals together with the FM-MX filter and the pre-amplifier balance adiust- ment are located at the rear of the tape recorder ref. fiq. 2 and 3. MX-FILTER SWITCH cH.z cR cH.1 LOW PHONO RADIO LOW Fig. 2. The input terminols ond the FM-MX filter switcn. PREAMP. BALANCE 4 OHMS OUTPUT CH.1 ADJ. SPKR. CH.2 cH.1 HIGH CH.2 HIGH HEAD. 4 OHMS PHONES SPKR. CENTER CH. CH.1 a PREAMP. 4 OHMS CENTER 4. OHMS OUTPUT CH.2 SPKR cH.2 CH. SPKR cH.1 iqi $;rii :,1 i! I Fig.3. The output terminols ond the bolonce odiustment. MICROPHONE INPUT5 The model series l2 is available with two different microphone contacts. The European version is furnished with DIN connec- tors ref . fig. 4. The US version is furnished with standard telephone iacks ref . fig. 5. Both versions have the same specification: Inpul impedance 200 ohms unbalanced, input sensitivity 150 trv. Fig. 4. Fig.5. A (.t ) t/ cH2 ) V cHt 200 n Mtc 4.0 The mechanism, detailed description and adiustment instruction The main f unction of the mechanical system is to drive the turntables and the capstan in the different modes of tape molion. The mechanical function is activated by the operating lever. + , $ ass a F Fig. 6. Top view, wilh lop cover removed. 4.I THE OPERATING LEVER The operating lever (54.1) has five positions and is located at fhe right front corner of the tape recorder: Normal forward drive, fast forward drive, fast rewind, free, and neutral. The operating lever activates the following parts: The motor switch (33.2): disconnects the power to the motor (14.1) in neutral or free position of the operating lever, and activates the elec- tronic beam indicator in nor- mal forward drive, when the fape recorder is set to record mode. ) ; The eccentric segment (59.17)l guides the pressure wheel assembly (5.l.3) and the lift- ing arm (59.i8). activafes the clutches under both turntables (65.1 , 65.2). ) The trip bar (52.I): 4.1.1 The motor switch The microswitch (33.2) is located on the bracket (54.9) for the operating lever, ref. fig. 7. The switch is con- nected in series with lhe motor current and is activated by the operating lever (54.i)to shut off the motor in neutral or free position. The motor switch also dis- iF connects the power to the electronic beam indicafors in neuiral o