Bell-RT75-tape-sm 电路图 维修手册.pdf

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1、PrtoroFAcr* FolJt SPEED CIANGE ON-OFF CONTROL RfdV IND- TONT CONTROL g RECORD BUTTON FAST FORWARD RUNSTOP CONTROL VOLUMT CONTROL MODEL R.T-75 3.SPEED TAPE RECORDE R AND PLAY BACK UNIT Manufactured by: BELL SOUND SYSTEMS, INC. A Subsidiary of Thompson Products, lnc. 555 Marion Road Columbus, 0hio fhi

2、s moleriol compiled ond published by HOWARD W. SAltS these same buttons act as Volume and Tone controls. Two output jacks permit use of an external speaker or high fidelity amplilier system. Aterminal stripinsidethe amplifier isavailable for 500 ohm out- put, at 30dbm level. A removable cover plate

3、on the bottom of the cabinet allows easy access to tubes, motor, fan, hum adjustment, and 500 ohm output terminal. Built in interlocks prevent the operator from placing the machine in more than one mode at a time. This prevents tape brealage, spillage, or accidental erasure. Page 2 SPECIFICATIONS Si

4、ze: 16 3/ 8 x 15 x 9 V 8 less hardware. Weight: 35 lb. approx. Power Required: 110-120 volts 60 cycle A. C. only - td-6wffi- Overall Frequency Response: 30 to 10,000 cycles at ?-luT. trs:- fier - TV. Push buttons provide for Fast Forward and Inputs (three): 2 microphones, I radio-phono-ampli- Output

5、s (two): External Speaker, actual impedance 3. 2 ohms - use any speaker 4 to 16 ohmsl External Amplilier, high impedance. Power Output: 3 watts. Speeds (three): Play or Record. 7 I/2, 3 3/ 4, or i-?/8-Effis per second. Fast Forward: 1200 ft. in 90 seconds. Fast Rewind: 1200 ft. in 70 seconds. Wow an

6、d Flutter: Less tian .25% at ? V 2 I. P. S. Speaker: 6rr x 9r heavy duty oval, RadioFans.CN 收音机爱 好者资料库 Type of Erase and Bias: Iligh Frequency (A. C. ) 60KC. Tube Complement: 1-12AY7 or ECC-83, l-12AX7, 1-6C4, l-6V6cT, 1-6X5cT. Controls: 1. Speed Change, On-Off Control. 2. Run-Stop Control. 3. Recor

7、d Push.Button. 4. Tone and push button rewind. 5. Volume and push button fast forward. OPERATI NG INSTRUCTIONS Preparing The Bell For Recording- 1. Place the recorder on a flat surface and remove the eover. Make certain that the Run-Stop control is in the Stop position and that the Speed control is

8、in the Off position. 2. Insert the A. C. power cord plug into a con- venient 110-120 volt, 60 cycle A. C. outlet. Threading The Tape- 1. Place a reel of rtA, wind tape on the supply reelsupport (6) and an empty reel of the same size on the taleup reel support (8). 2. Unwindabout two feet of tape. Ho

9、ld a section oftapestraightwith both hands and insert the tape into the tape slot. Insert the free end of the tape into one of the radialslots in the hub of the empty reel. Rotate reel counter clockwise three of four turns to secure and take up all slack between reels. To Record From Microphone- 1.

10、Turn recorder on by placing speed control knob (1) in tte speed position desired. Allow approxi- mately 30 seconds for the unit to warm up. Insert the microphone plug into the Mic. I input jack. Use Mic. 2 input jack only when using two microphones or when mixing with Radio, Phono., or TV programs.

11、If microphone is set on a hard surface, place sponge rubber or several thicknesses of cloth underneath it to absorb any vibrations, Set record level before recording by depressing the red record button and observing the flash of the neon record level indicator. While sound source is striking microph

12、one, carefully adjustthe volume control so thatthe levellamp flashes on peak passages. NOTE: Correct recording volume is very important. If the neon level lamp flashes all the time, the recordingwill be overloaded and distorted on playback. If level lamp does not flash at all, playback will be weak

13、and contain high background noise. 2. After level adjustment has been set, turn the run-stop control (2) to Run. Thetape is now moving and any sound entering the microphone will be re- corded on the tape. When recording is finished, turn control (2) to Stop. To Record From Radio. Phono. Or TV- Recor

14、dings can be made from a radio or tele- vision reeeiver by placing the microphone near the loudspeaker, howeverthis type of recording is usually not satisfactory beeause of background noises picked up by the microphone and lack of good quality. A better recording can be made by connecting the Radio

15、inputof the recorderto the radio or TV voice coil ter- minals, In the case of an AM-FM Tuner, connect to the tuner output. Dual Track Operation- NOTE: Recordings are made on half the width of the tape at one time. Since it is impossible to edit and splice one track without affecting the other, recor

16、dings which are to be edited should be limited to one track. l. After a reel of tape has been recorded, a second track may be recorded on the same reel (without rewinding) by removing the full reel from the right hand spindle, turning it over, tten placing on the left hand spindle. Placethe emptyree

17、l onthe right hand spindle. 2. Rethreadthe tape andproceedwiththe record- ing as previously described. 3. Afterthesecondtrack has been recorded, the first track is ready to be played without rewinding, by changing reels as described in Step #1 above. To Rewind- After a recording is made, tape maybe

18、rewound by pushing Rewindrrknob downpositively. Itwill lock in position Fo it is unnecessary to hold down. When desired portion of tape is rewound, push down and release IFast Forwardrr knob. This will stop ttre tape. When rewinding a complete or large portion of a reel, it is better to take tape ou

19、t of slot and run straight across from reel to reel. Thissaves wearonthe head and is somewhat faster since it eliminates the drag set up by the tape running through the head slot. To Play A Recording- l. To play back recordings, place reels on reel supports and tlread as previously described. Turn t

20、he speed control pointer (1) to the correct speed; this alsosupplies power tothe motor and amplifier. Plaee the run- stop pointer (2) in the Run position and adjust the Volume and Tone controls for desired listening level. If speed of tape is unknown, the speed control pointer (l) can beturned after

21、the unitis playing. After the recordings have been played, return the run-stop pointer (2) to the Stop position. This releases the pressure roller (22) from the capstan and stops te tape. 2. After the first track has been played, the second track may be played, without rewinding, by turn- ing the re

22、els over and placing them on opposite reel platforms. This may be done at any time during playback. NOTE: When recordings are played back thru the built-in speaker, remove anyphone plug which may be inserted in either the External Speaker or High-Z output jacks. These jacks, when used, disconnect th

23、e built-in speaker. Fast Forward- In playback, it is sometimes desirable to skip portions of tape to a particular spot. To do this, push down and hold Fast Forward knob until tape arrives i =/ =o Hr FrlF nF I lrr Page 3 RadioFans.CN 收音机爱 好者资料库 Figure 2 at desired spot. To stop tape, release the Fast

24、 Forward knob. To prevent unnecessary head wear, tape should be taken out of head slot when large por- tions of a reel are to be skipped. D I SASSEMBLY I NSTRUCTIONS Top-Deck Plate- To service parts located directly under the top- deck plate (5) it is not necessary to remove the unit from the case.

25、Remove top-deck plate as follows: Remove four screws (one in each corner of the turned down flange) and use a #10 spline wrench to remove the two pointer knobs. Lift top-deck plate straight up. To Remove Recorder From Cabinet- To remove recorder from cabinet, first remove the top-deck plate (5). Nex

26、t, removethe three screws fromtherearof the cabinet located just above the vent grille. Remove four screws from the bottom of the case and liJt recorder straight up. Remove speaker leads before lifting recorder completely out of case. To Remove Amplifier From Transport Mechanism- For some mechanical

27、 adjustments on the bottom of the tape transport mechanism, it will be necessary to irst remove the amplifier. Remove as follows: Remove three sheet metal (hex. head) screws from each side plate. Remove four hex. head screws fromthe jackand lamp brackets, 2 each side. Remove Page 4 head plug and mot

28、or plug from their sockets. Loosen the three Phillips head screws in the right hand side plate so that the amplifier and power cord will miss flanges as the mechanical unit is lifted straight up. Tighten the three Phillips head screws in the right hand side plate and place the mechanical unit on a f

29、lat surface. ADJUSTMENTS When the amplifier is removed from the mechani- cal unit, tape may be placed on the unit and driven in anymodelbyusinganAC power cord with a socket that willfit the motor plug. On units with serial #14, 000 to 15,200 use a Bell part #B-20209P19 socket. On units above serial

30、#15,200, use a Bell part #B-20209P29 socket. Rewind Belt Adjustment- Leave 12 to 15 turns of tape on the take-up reel (right hand) and push rewind button all the way down. Tape should start in motion. Il the recorder meets this test, shutoff the motor with speed control pointer (1). Place run-stop p

31、ointer (2) in the run position. Now start the motor by placing speed control pointer (l) in the 7 I/2I.P.S. position. The motor shoutd starttapeunderload, not stall. If motor stalls, re,vind belt (6?) is too tight. If machine fails to rewind last few turns of tape, rewind belt (6?) is too loose. Mak

32、e adjustment as follows, if necessary. Remove the reels and loosen the two screws (l/ 2 turn) which mount the rewind idter pulley assembly (66). To loosen belt, reach under bottom plate and slide the rewind idler pulley assembly (66) toward the Figure 3 front and to the left. To tighten belt, move i

33、dler as- sembly (66) toward the rear and to the left. Move the idlerassemblyaboutl/ 32, at a time, theninstall reels and re-make tests. Fast Forward Adjustment- Leave 12 to l5 turns of tape on the left hand (supply) reeland push fast forward button all the way down and hold. Tape should start to win

34、d in forward direction. . Next, holdright hand (take up) reel from turning (do not press down). Observe the take-up belt (?3), it must be turning and clutch plate (9) must be slipping against the take-up reel support (8). when the fast forward button is held down. If take-up belt (?B) does not turn,

35、 it is too loose. Male adjustment as follows, if necessary: Loosen the fast forward adjustment screw (see Figure 2) about I/ 2 twn. Totighten belt, reach under bottomplate and slide the fast forward and play pulley assembly (71) away from the take-up reel support (8). Move very little at a time as t

36、his adjustment is very critical. After adjustment is made, tighten screw. Check adjustment as follows: 1. Do not load tape on recorder. 2. Place run-stop pointer (2) in the Stop po- sition. 3. Place speed control pointer (l) in one of the three speed positions. 4. Graspthemajorbrake assembly(12) and

37、 pivot it toward the front of the recorder. The take-up reel support (8) mustnotturnwhen the bra-kes are released. lf reel support (8) turns, belt (?3) is too tight. Brake Adjustments - (Refer To Figure 5)- Check brake operation as follows before making adjustments: l. Placeafull ? reeloftape on the

38、 take-up reel support (8) and an empty reel on the supply reel support (6). Do not place tape in head slot but run straight across from reel to reel. Place recorder in Rewind position andwhen tape is up tofastest speed, stop tape by depressing the Fast Forward button. Release immediately. Tape must

39、not spill or throw loops. 2. Place nearly a full reel on the supply reel support (6) and thread tape straight across from reel to reel (not through head slot). Placerun-stopcontrol in the IRun position (this eliminates holdingfast for- ward button down). When tape has reached fastest speed, place ru

40、n-stop control in the ilStoptposition. Tape must not spill or throw loops. If brakes require adjustment, do so as follows: 1. (Forunitswith serial #14,000 to 15,200 only). Checkthetwo dimensions as shown in Figure b. Mea- sure from inside bottom plate flange to edge of brale pivotbracket. This shoul

41、d measure 2l/4,. Toadjust for both dimensions, loosen the two screws (A) and re-position the brake pivot bracket. 2. (This adjustment is for allunits). Check space between brake lever cam and brake lever (35). There should be some play, about I/ 64. Also check to see thatthebrakelevercam is approxim

42、ately in the center of the control arm slide (45). Test brake release in Fast Forward, Rewind, and Run. Brakes must release in all three positions. =o Hr Fll| F VF I gt Page 5 Figure 4 To change clearance betweenbrakelever (35) and brake lever cam, loosen scretvs (B) holding brake lever bracket, Mov

43、e bracket forward or backward. to obtain t:.e I/ 64 spacing. Use this same adjustment to center cam in control arm slide (45). Move bracket to right or left to obtain correct spacing. NOTE: (Forunits with serial #14, 000 to 15, 200 only). If brakes release more in one direction than another, that is

44、 more in fast forward than in rewind or visa versa, this can be equalized bysliding the brake lever bracket to the rlght or left after loosening screws (B). Speed Slide Cam And Damper Adjustment- ;ure r-)= l. (For units with serial #14,000 to 15,200 and for units with serial numbers beginning with 2

45、5,000, 35,000 and 45,000). Speed cams (40), (41), and (42) must clear the control pins (point C Figure 2) by approximately V 16 when that particular slide is en- gaged. Positionof motor on motor mounting plate and positionof motor mounting plate on spacers will effect this. See paragraph on motor mo

46、unting. The control pins (point C Figure 2) must be in the center of the speed cam notch(40), (41), or (42), when that particular slide is engaged. To adjust, loosen set screw and turn cam. Spacing betrveen the phenolic slides should be such that they are parallel Page 6 to top and bottom plates. If

47、 a phenolic ryasher is used above cam, spacebetween cam and slide is about .008 inch, if no rfasher, about .025 inches. Slide cam (40), (41), and (42) up or down to adjust. Adjust bottom cam (42) first. 2. (For units with serial #14, 000tol5,200only). The phenolic slides must clear the sides of spee

48、d slide bracket (44) when that particular slide is engaged. Speed slide bracket (44) should be located as near the motor pulley and pressure roller (22) as the mounting slots will permit. This will allow ful1 use of the slide springs, 3, (This applies to all units). The speed slide dampers (point D

49、Figure 2) must press down firmly on the phenolic slides to hold idler wheels in position when engaged. However, this damper spring must not interferewiththesmooth operation of the slide against its spring tension. Adjust damper springs carefully with mounting screws on side of speed slide bracket (44). Capstan Actuating Cam (30) Adjustment- The capstan actuating cam (30) must have some end play between top plate (2a) and the capstan pres- sure arm (27). Also, there must be some play between cam (30) and flywheel (29). To adjust, turn run-stop control (2) to Run. Loosen set screw in