BellSound-RT204-tape-sm 电路图 维修手册.pdf

PnoToFAcr* FolJ.t $ ao zcl e* o4 laJ .Et fo Hg En e= lll r - la pO 1F irZ o9 $ GENERAL I NFORMAT ION The Bell Model RT-204 is designed to record and play back two tracks of material on standard width recording tape (/ 4), which doubles the playing time of a standard 5r or ?rt reelof tape withno loss of frequencyresponseorquality. Recordings canbe made from a radio, television receiver or phonograph, in addition to those made directly from the microphone. Recordings can be played back through the self-contained speaker or external speaker through use of the External Speaker Jack. The Bell Model RT-204 has two tape speeds, 7 / 2rt and 3 3/ 4tper second. Using both tracks, the recording time is as followed: Size Reel 3 3/ 4rSpeed 7 V 2 Speed 5 (600 ft. ) 7 (1200 ft. ) I hour 2 hours I/ 2 hour I hour The Bell Model RT-204 is designed to operate on 60 cycle, 110-I20 volts, AC supply only Manufactured by: BELL SOUND SYSTEMS, INC. A SUBSIDIARY OF THOMPSON PRODUCTS, INC. 555 MAR ION ROAD COLUMBUS, OH IO fhis molerial compiled ond published by HOWARD W. SAtS thendepress Stop key. Be surekeys arepressed all theway down. Wait forthetape to stopbeforepressing the Play key. FIGURE 2 D I SASSEMBLY I NSTRUCTIONS AD J U STMENTS To Monitor Recordings - Any signal being recorded may be monitored by plugging high or low impedance phones into the Spkr. output jack. An external amplifier may be used to monitor any signals being recorded if connectedto the Amp. jack. An external speaker may also be used. Use Spkr. output jack. To Remove Recorder From Cabinet - Remove the four Phillips-head screws located at the edgesof the top deck plateand lift theunit straight up from the case. Disconnect speaker leads from speaker before lifting unit completely out of case. Head And Pressure Pad Adiustments - To properly check rread azimuth alignment it is necessary to have a pre-recorded 1 mil alighment tape which results in a ?500 cycle per second signal when operated at 7 l/2 inches per second. PIay alignment tape back through recorder with an AC VTVM connected across the speaker or 6Qload. CAUTION: Be sure recorder is in Play position to prevent erasure of alignment tape. Three things can cause low meter readings (pro- viding amplifier and tubes are working properly). These are, dirty headrimproper pressure pad pres - PAGE 4 sure, or wrong head alignment angle. Check these things as follows: 1. Check head to besure there is no dirt on the pole pieces or bakelite portion. Dirt holds the tape away from the pole pieces and lowers output. If head is dirty, clean with head cleaning solvent or alcohol. Wipe dry immediately after cleaning. 2. Check that pressure pads (22 and 23) cover the head pole faces. The pressure at the spring side of the play-record pad (23) should be 30 grams and thepressure at the spring sideoferase pad(22) should be 20 grams. Bend pad springs only when necessary, avoiding odd-appearing kinks in the springs. FIGURE 3 tE etr lll r - ta pO :C irZ oE 5 3. To adjust head alignment by means of tape guide heights without destroying the correct nominal tape height at the head, proceed as follows: Set both left and right tape guides (29) to .486 (at top surface) off of panel. With head fully seated, run the ?500 cycle alignment tape through the machine withthe Volumel and Tone controls full on. Adjust the left tape guide by rotating not more than plus or minus L/2 twn (*.016). If this fails to produce a peak voltage reading on the AC vacuum tube voltmeter, adjust the right tape guide by not more than +1/4 turn (+.008). This amount of adjustment will tilt the tape by morethan the normal head mis-alignment andif no peak is reached either the head is not fully seated or the head mounting plate (1a) is bent, or the head itself is worn. Tape position must be such that, when playing back a tape having the opposite track recorded to normal level no crosstalk will be audible in the play - back (slight crosstalk may be audible in ideal listening conditions). ReeI Platform Adjustment - The reel platforms (2 and 3) must clear the deck plate by l/32 minimum - t/16 maximum and both reel platforms must be the same height on a given machine. Adjustment is made by loosening set screw (a) and positioning reel platform (2) or (3) to the cor- rect height. After adjustment is made, tighten set screw (4). Hum Adjustments - The hum balance control (R3) on the amplifier should be adjusted first for minimum amplifier hum but wiII probably have to be slightly re-adjusted for Iowest overall hum, i.e., the hum voltage will help cancel hum induction into the head from the power transformer and motors. Minimum hum voltage in playback is obtained by correctly polarizingthe power transformer and motors, correctly polarizing the line cord plug, adjusting the hum balance pot for minimum hum, and selectingthe pre-amp tube (V1) if necessary. Procedure for Motor Fhasing - in PIay Position But Without Tape. 1. With aII motors disconnected and the head shorted, the amplifier should have only a 10 to 15 mv hum output. With the head connected, hum is from the power transformer and should be under 50 mv. This can be reduced by shimming the transformer mounting spacers to tilt the transformer (only neces- sary in extreme cases). 2. PIug inthe take-up motor (45) inthe direction giving lowest hum. Check hum balance control (R3). 3. Plug in capstan motor (62) in the direction givinglowest hum - donot change take-up motorcon- nections. Check hum balance control (R3). Brown wire on common should be minimum. 4. Plug in rewind motor (a1) in the direction giving lowest hum. This motor will introduce l2O cycle hum which willnot be helped by the humbalance control, however it sometimes affects hum balance stightly and the hum control should be adjusted after this last motor is connected. Measure hum Volume control minimum. output voltage across 6O load, maximum and Tone control PAGE 5 A PHOTOFACTEXPLODED VIEY Howard 7. Sams never use carbon tetra- chloride rvhen cleaning any rubber driving surface. CAUTION: Topreventscratchingthe headpolepieces, never use a metal tool when cleaning the play-record-erase head (13). LUBRICATION 3. Apply one drop of #10 motor oil to the top and bottom capstan bearings. Caution: Afteroiling these bearings be certain that no oil seeps onto the rubber idlers (5? and 72) or onto the portion of the capstan shaft which extends above the top deck plate. 4. Apply one drop of#10 motor oil tothe pres- sure roller bearing (17). NOTE: Only a very small amount of oil is needed on each bearing. It is desirable to use too little rather than too much for Iess trbuble is likely to result. OiI onthe rururing surfacesbetween the motor pulleys and the rubber idlers is often a cause for poor or no drive as well as excessive wow and flutter. AND REMED IES operating the recorder in the 3 3/4 inch per second speed position. Replace spring (61). Take-Up ReelWill Not Take Up Tape In Play Or Record Position - 1. Set screw (4) in take-up reel platform (3) loose, causing the reel platform to slip on the motor shaft. Tighten the set screw. 2. Resistor (R26) open. Replace. Recorder Will Not Rewind Tape - 1. Set screw (4) in supply reel platform (2) loose, causing the reel platform to slip on the rewind motor shaJt. Tighten the set screw. Dynamic Brakes Do Not Frnction Properly - 1. Check selenium rectifier (M1). 2. Check resistors (R25 and R2?). If either of these resistors is open, there wiII be no hold-back tension on the reurind reel when in the PIay or Record mode. 3. If, when going from Rewind to Stop, tape spills from the take-up reel(3), check resistor (R25). 4. If, when goingfrom Fast Forwardto Stop, tape spills from the rewind reel (2), check resistor (R2?). Normal DC voltages for selenium reqtifier (M1) and motors (41) and (45) are as follows: Selenium rectifier (M1), lPlay position - 30 volts DC. Rewindmotor (41),Flay or Record- 8 volts DC. Rewind motor (41) in Stop after Flay or Record - 28 volts DC. Take-up motor (45)in Stop after Play or Re- cord - 1? volts DC. 1. Check aII tubes, inspect wiring and function switch (Mb) for poor or open connections. 2. Test all four jacks for open or shorted cir- cuits. These jacks mustnot groundagainstcover plate (e). 3. Refer to schematic for all voltage and re- sistaJrce readings. 4. Test bias oscillator as follows: Connect a AC vacuum tube voltmeter across the erase head wind- ing atthe play-record-erase head socket. Due to high frequency, use unshieilded wiring. Place recorder in Record position. Voltage should be 50 to 68 volts. Check bias and erase frequency with a signal generator and scope. This should be 58 to 65 kc. AMPLIFIER TESTS AND REPAIRS EI.TCTRICAL PARTS LIST Check bias voltage across play-record head winding at the play-record-erase head socket. A. 30 to 50 volts atl L/2 inches per second. B. 10 to 1? volts at 3 3/4 inches per second. 5. The play-record-erase head may be tested for continuity ii suspected of being open. The erase winding should be approximately 10 ohms and the play- record winding about 160 ohms. CAUTION: Whenever the headis tested for continuity it willbecome magnetized to some extent. Therefore, always demagnetize head aJter testing. En (,tr mr l -o :C pz o9 5 Ref. No.Part No.Description Ref. No.Part No.De6cription V1 v2 V3 v4 C1A c1B c1c c2A c28 czc c3 cq c5 c9 c10 c11 cl2 c13 c14 cl5 c16 c17 c18 cl9 R1 R2 c6 c7 C8 R3 R4 R5 R6 R? R8 R9 B-20048P28 B-20048P28 B-2004?P98 B-20047P14 B-20t4tPt B-20047P81 B-20049P87 B-2004?P86 B-20047P81 B-2004?P86 B-20047P1? B-2004?P96 B-20049P98 B-20047P81 B-20049P87 B-20047P81 B-20047P1? B-20049P? B-20049P64 B-20066P106 B-20066P108 B-20066P72 12AX?, Pre-Amp. 6SN?GT, Bias Osc,-AF Amp. 6V6GT, Audio Output 6X5GT, Rectifier Cap., Elect., 20 mfd. 450 V. Cap., Elect., 20 mfd. 450 V. Cap., Elect., 50 mfd. 50 V. Cap., Elect., 20 mfd, 450 V. Cap., Elect., 20 mfd. 450 V. Cap., Elect., 50 mfd. 50 V. Cap., Molded Tub., .1 mfd. 200V Cap., MoldedTub., .0013 mfd. 400 v. Cap., Ceramic Disc, 101000 mmi 500 v. Cap., Molded Tub., .05 mfd.400 V. Cap., Mica, 4?0 mmf. 500 V. Cap., MoldedTub.,.005 mfd. 400 v. Cap., MoldedTub., .05 mfd. 400 V Cap.,Molded Tub, .005 mfd.400 V Cap.,Molded Tub., .002 mfd,400 V. Cap.,Molded Tub., .1 mfd. 400 V. Cap.,Mica, 150 mmf. 500 V. Cap.,Molded Trb., .05 mfd. 400 V Cap., Mica, 470 mmf. 500 V. Cap., Molded T!b., .05 mfd. 400 V. Cap., Molded Trb., .002 mfd. 400 v. Cap., Mica, 100 mmf. 500 V. Cap., Mica, 2?0 mmf. 500 V. Volume Control, 1 meg. Tone Cont. and On-Off Switch, 500 KC. Ilum Adj. Cont., 100O Resistor, 470K O, l/2 walt Resistor, 1500 f, 1/2 watt Resistor, 10 K o, 1/2 Watt Resistor, 4.7 meg.,L /2 Watt Resistor, 68 K r, 1/2 Watt Resistor, 4.7 meg., l/2 Watt R10 R11 R12 R13 R14 Rl5 Rl6 R17 R18 R19 R20 R21 F.22 R23 R24 R25 R26 P21 R28 R29 R30 R31 R32 R33 T1 T2 sP1 L1 M1 M2 M3 M4 M5 M6 M7 M8 M9 Ml0 Ml1 Ml2 B-20256P18 B-20256P16 B-20256p1? B-20256P15 B-20366 B-20352 B-201 11P29 B-23704 B-2010?-P10 B-20043P31 B-25251 A-25342 B-20209P30 B-20209P20 B-20209P32 B-20209P32 Resistor, 4.7 meg.,l/2 Watt Resistor, 4?0 K O, l/2 watti+s% Resistor, 4?0 K f,l, l/2 Watt Resistor, 33 K A, 1/2 Watt Resistor, 820 A, l/2 Watt Resistor, ?500 O, 1/2 Watt Resistor, 1 meg., 1/2 Watt Resistor, 1500 A, l/2 Watt; +5$ Resistor, 470 K f, l/2 Watt Resistor, 100 K f, L/2Waft Resistor, 390 A, 1 Watt Resistor, 2.2 meg.,l/2 Watt Resistor, 2?0 K O, 1/2 Wtt Resistor, 100 K O, l/2 Watt Resistor,6 f, 4 Watt Resistor, 150 A, 5 Watt Resistor, 200 O, 10 Watt Resistor, 50 O, 5 Watt Resistor, 21 K A, l/ 2 Watt Resistor, 10 K C, 1/2 Watt Resistor, 4?0 Q, 1 Watt Resistor, 470 Q, 1 vratt Resistor, 27 O, l/2 Watt Resistor, 47 K A, l/2 Watt Power Transformer O:tput Translormer Spealcer, P.M.; 5 l/4 inch Round Bias Osc. Coil Selenium Rectifier Fuse, Pig-Tail - 3 Amp.GJV Pilot Lamp, #4? Neon Lamp, #NE-51 !nction Switch Leaf Switch, Memory Br4king Switch Motor Socket, I Pin Head Socket,4 Pin Mic. Input Jack Radio Input Jack Ext.AmpI. Ortput Jack Ext. Spkr. Ortput Jack PAGE 9 AMPLIFIER - FRONT VIEW 65N7GT I2AX76X5GT 6V AMPLIFIER - REAR VIEW PAGE IO ;H Etr tnt IUl nO e $2 oe I tr) * (o cO -_ ogd; ; 3e E E FE aE E= s =EEEi : EE:5 EEE =ef.-*EFis !e =E; F fra 5 H= H E g ! iE; scs E g E gEE i:E E :E =E5; BFEP:;E ;frEEEE: -; iri.cri < T UEET U ci U F 2 (9 Itt I4J 6 lai r/, = c, u !F o t/l tt u J z J z. o =tn o o- 5 l =z. u !z F ttt F =z =o uF 9 #18 =a= u o= I -;- -; b,6666 2 : E ts UI CL -. Jl z. o F (-) U VI F =o e. L 5 o- !< o 6 )tcil =o F a(-) 96 tt l- z. o e. r Ir, z o o= d ir <ii =(/roaF oz. Lcle, 5 Ir 2 o =E =Yr UF Ezo d L -r11, -l I I (o F x$l () lr)Ct qt e. o F d)O = -o F (l J -o c)9a LF,-z =ol/)o rU LZ. oo IF =2. vo E 2 o 6F ezl ol I /a tNt e=,/ E E o N ifit 6q G)E -,lF I o : = o ts -f = o ts -t o r) x e o -Cl- 6., z8 6- EE N; i; F! gAs F LJo <I $o o Ic el vl !zlrl I R6 F g OF <= da_ 6= z o - a- l ol ll - z. O AF e(J gfr UF e. z. c - o to (t o ro 6t IE IE lo IN L$l, = ts sl *AF xE sE * -+a-r E /6 g-E =-Jv4. )/ .o 3r J- !z o N /i, o o z. o F c) l4I v, F =o e. r PAGE II MECHANICAL PARTS LIST Ref. No-Part No.Dese.ription Ref. No.Part No.Description 1 2 3 4 5 6 7 8 I 10 11 12 13 t4 15 16 t1 18 19 20 2l 22 23 26 21 28 29 30 31 32 33 34 35 36 24 25 A-25328 A-25328 B-25292 B-20148P51 B-20148P51 D-25291 A-25264 A-2531 I 9-23721P2 A-25402 A-23822 A-23?63P2 A-23518P1 B-20089P48 A-25315 A-25270 B-2540? A-25334P1 A-25331 B-25332 A-25265 A-25391 A-25269 A-25268P1 #14 Crutch Iip, l/4 r.D, Reel Platform, Supply Reel Platform, Ta.keup #8-32X 3h6 Set Screw, Bristol Cup Point Head Cover #6X1/4 Sheet Metal Screw Tone Control On-Off Knob Volume Control Knob Cover Plate #8lL/4 Sheet Metal Screw Head Retaining Spring Head Cover Bracket Play-Record-Erase Head Head Plate Retaining Ring Nylon Washer Pressure Roller Assembly #6 - 32)l / 4 Screw, Phillips Binder Head Flat Washer SIide Bearing Pressure Roller Spring Erase Pressure Pad Assy Record Pressure Pad Assy Felt Pad Lock$rasher nE42Xl/4 Phillips Rd, IId. Mach. Screw Presaure RoUer Actuator Assy Hex. Hd. SeIf Tapping Screw Cover Plate Retaining Clip Tape Guides Record Latch Assy #6-32X1/4 Philtips Flat Hd. Mach. Screw Tinnerman Push Nut Shaft Key (6 used) Stop-Rewind- Forward Key Actuator Play-Record Key Actuator 3? 38 39 40 4t 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 6l 62 63 64 65 66 67 68 69 ?0 7t 72 ?3 74 75 76 77 A-25268P2 B-20089P58 D-25340 B-25400P1 B-25400P2 A-25399 A-25394 A-25389 B-20089-P26 B-25386P1 A-25397P1 B-25388 A-25395 B-20025P23 B-20029P41 A-25397P2 A-25382 A-25406 B-25386P2 B-25381 A-25257 Record Key (red) Fibre Washer (13 used) Deck Plate Assembly #6-32 X 1 Hex. Hd, Mach. Screw Rewind Motor I-ockwasher #6 Hex. Nut #6-32X1 Hex. Hd. Mach. Screw Take-up Motor Lockwasher .#6 Hex. Nut Gasket Motor and Capstan Mtg. Housing #S-32XL/4 IIex. Screw Capstan Lever WeId Assy Spring Washer Shoulder Washer #6 Hex. Nut. Capstan Shaft FeIt Washer Capstan Drive Wheel, 1 l/2 l.P.S. RoII Pin #6-32X1 f/4