Scott-LT-111-Operation-Manual 电路图 维修手册.pdf

《Scott-LT-111-Operation-Manual 电路图 维修手册.pdf》由会员分享，可在线阅读，更多相关《Scott-LT-111-Operation-Manual 电路图 维修手册.pdf（16页珍藏版）》请在收音机爱好者资料库上搜索。

1、ANUA:C SCOTI STEREO TUNER RadioFans.CN 收音机爱 好者资料库 LOOK HOW EASY IT IS TO OPERATE YOUR 3708/LT-lll STEREO TUNER This simplified photo-guide shows how to use your new tuner. A similar guide on the inside back cover shows how to connect the tuner to the rest of your music system. However, TUNING INDICA

2、TOR - For best listening, adjust the tuning dial so that the vertical dark band in the center is nar- rowest. (see pages 5 and 8) i!LEC:101 tlt SP iJi?FT SELECTOR Off -turns the tuner off (see page 7) Mono-To receive FM mono- phonic broadcasts (see page 10) Stereo -To receive FM stereo broadcasts (s

3、ee page 9) we strongly suggest that you read the complete instruction book thoroughly. Only then will you get the utmost enjoy- ment and maximum performance from this superb instrument. FM TUNING DIAL - To select an FM station (see page 8) Monitor -Helps you locate a station broadcasting in stereo.

4、Turn Selector to Monitor posi- tion and tune slowly across the dial. When you hear a steady tone, return the switch to Stereo. (see page 10) TYPE 3708 L T-111 uses different panel but has same controls as 370 pictured above. RadioFans.CN 收音机爱 好者资料库 -ORCHESTRA 4 a LEFT RIGHT a B MICROPHONES B ITR II!

5、.- ,_ I MONOPHONIC FM TUNER MONOPHONIC AMPLIFIER HOW FM STEREO (MULTIPLEX) WORKS Multiplexing is a method of broadcasting two or more signals from one FM transmitter. This means that a single FM station can broadcast both the left and right channels of a stereophonic program from records, tapes, or

6、live performances. To enjoy FM stereo pro- grams, you need a stereo amplifier (or two monophonic amplifiers) and two speaker systems, in addition to your new Scott tuner. How Multiplex Stereo Works Humans are capable of hearing sounds between about 20 and 20,000 cycles per second. Any sound above 20

7、,000 cycles per second is referred to as supersonic because it is above the range of human hearing. Most good FM tuners are capable of reproducing these super- sonic frequencies above 20,000 cycles per second (cps for short). Though you cannot hear them, these supersonic frequencies are used very ef

8、fectively for multiplex. At a frequency of 38,000 cycles per second (cps), high above the sounds you can hear, the second (stereo information) signal is added on. While you cant bear this second signal, your FM tuner can, and, if equipped for multiplex, will con- vert this into sound you can hear -s

9、tereo sound. This second signal is not either the left or right channel. If it were, a listener with a monophonic tuner would hear only half of the program. Instead (see diagram below), a method is used that pro- vides the full monophonic signal (left plus right) for the listener with a regular FM t

10、uner, and stereo for the listener with multiplex equipment. The stereo quality depends on how well the multiplex FM MULTIPLEX STEREO TUNER c6l .,., I STEREO AMPLIFIER -a ci a ., o a o LEFT RIGHT SPEAKER . SPEAKER _ ., :-,._ =:-: - -,., -., - - tuner handles the second signal (stereo information). If

11、 very little of the second signal is being properly processed, there will be poor stereo quality (poor separation between the left and right channels). .Simply having sound from both speakers does not necessarily mean you have stereo. Conventional narrow-band tuners cannot give the fine stereo quali

12、ty obtained with Scott Wide-Band tuners. As the FCC pointed out, the approved multiplex stereo system . like any multiplex transmission system, will increase energy transmission at the edges of the channel involved. Accordingly for opti,num stereophonic recep- tion, the (tuners) bandwidth . . . must

13、 be considerably greater than that of monophonic (tuners) . *Scott tuners have always had the wider IF bandwidth needed. Since stereo FM broadcasts are such an abundant source of high quality program material, many listeners will want to make off-the- air stereo tape recordings. In many instances, h

14、owever, conventional multiplex circuitry causes interference with a tape recorder, result- ing in whistles and beeps being recorded on the tape. Scott multiplex units incorporate the expensive filters needed to prevent this inter- ference. Scott equipment can be used with any tape recorder. New FM S

15、tereo will bring you thrilling broadcasts of world famous symphony orchestras and opera companies . intimate close- ups of jazz in stereo . dramatic presentations with life-like move- ment. You will hear the wonderful new sound of FM multiplex stereo in your home . and using Scott equipment, you wil

16、l be able to make flawless off-the-air stereo tape recordings. *See paragraph 86, FCC Report and Order,DocketNo.13506,4/ 19/61. 2 RadioFans.CN 收音机爱 好者资料库 3 HERES WHAT MAKES SCOTT TUNERS SO OUTSTANDING FM stereo multiplex reception makes more severe demands on a tuner than regular monophonic receptio

17、n. You will undoubtedly enjoy your new Scott tuner much more if you have some understand- ing of the unique engineering that makes these tuners so outstanding. Below are some of the various factors that go into the design of a Scott tuner. ALUMINUM COPPER Usable sensitivity-indicates a tuners abilit

18、y to receive weak sig- nals with very low hum, noise and distortion. Scotts high usable sen- sitivity is in part due to the silver-or copper-plated front end on Scott tuners. The high conductivity of these metals preserves the full quality of even the weakest signals without introducing the noise, h

19、um or distortion of conventional tuners. Instead of inexpensive steel chas- sis, Scott uses electrolytic alumi- num with copper cladding in the critical IF and multiplex sections. Copper is a far better conductor than steel and eliminates the losses ordinarily associated with that metal. Aluminum, b

20、eing non-mag- netic, tends to reduce hum and noise, giving Scott tuners an excep- tionally high signal-to-noise ratio. Selectivity -is the ability to completely separate stations on nearby channels. Scotts Wide-Band IFs most closely approach the ideal by amplifying the desired signal and completely

21、rejecting all nearby stations. Scott tuners separate stations that conventional narrow-band tuners would pass by. Freedom from drift -a tuner must stay on station without wan- dering (or drifting). Narrow-band tuners use undesirable automatic frequency control (AFC) to pre- vent drifting. AFC introd

22、uces con- siderable distortion and reduces bass response. AFC also reduces se- lectivity because its magnetlike at- traction towarls stronger stations pulls away from nearby weak ones. Scott tuners utilize Wide-Band de- sign rather than AFC to eliminate drift, bringing you the full range broadcast w

23、ithout introducing dis- tortion. Stereo separation with loiu clis- tortion -a must for good FM stereo reception. Conventional nar- row-band tuners inherently cannot give as fine stereo quality as Wide- Band tuners. Scott-developed, Time Switching Multiplex circuitry pro- vides full frequency respons

24、e with extremely low distortion. Stereo separation far exceeds specifica- tions established by the Federal Communications Commission. INSTALLING YOUR SCOTT TUNER -MHIIEH-l Your tuner can be placed on a table or bookshelf, in existing fur- niture like an end-table, buffet, or room divider, or in a sp

25、ecially de- signed equipment cabinet. A hand- some wood accessory case is avail- able from your dealer. Wherever the tuner is placed, adequate provision should be made for ventilation. If this is not done, drift will occur in the FM section, and the life of the internal components will be appreciabl

26、y shortened. By adequate ventilation we mean some space above and behind the unit where air may circulate freely, or, if it is installed in a cabinet, an open back. If you install your tuner in the same cabinet with your amplifier, always place the tuner alongside the amplifier or underneath it- nev

27、er above it, since the amplifier produces much more heat than the tuner. Hot air tends to rise and if the tuner is above the amplifier, the heat generated by the amplifier will cause drift in the tuner. To help disperse heat rapidly, all Scott tuners employ aluminum in the construction of the chassi

28、s and panel. Aluminum is an excellent conductor of heat. Therefore, the panel may seem warm to the touch. As long as the unit is adequately ventilated, this is of no consequence. CONNECTING YOUR SCOTT TUNER TO A STEREO AMPLIFIER There are two sets of outputs for left channel and for right channel on

29、 the rear of your Scott tuner. Connect one of the two audio cables provided from the left channel ( audio or high ) output to the left tuner input on your stereo amplifier. Some amplifiers refer to the left input as Channel A. Connect the remaining audio cable to the right channel (audio or high) ou

30、tput to the right tuner input of the amplifier sometimes referred to as the Channel B input. For most applications the three foot cables provided should be more than adequate. Longer cables can be obtained from your dealer if needed but it is not recommended that you us.e cable lengths in excess of

31、ten feet. 4 5 TO A TAPE RECORDER FM multiplex stereo can be an excellent source of program ma- terial for home tape recording if interference effects can be elim- inated. These interference effects occur when the subcarrier that provides the stereo information leaks into the audio output of the tune

32、r and beats against the oscillator of the tape recorder. The re- sulting whistles and squeals would ruin any tape recording. All Scott tuners include a special filtering circuit which keeps the subcarrier from creeping into the output. This is another example of how ad- vanced Scott engineering prov

33、ides you with the maximum satisfac- tion from your equipment. Most stereo amplifiers provide tape recorder outputs which can be connected directly to a recorder. If your amplifier does not have these outputs, or if it is inconvenient to use them, a set of outputs on your tuner can be used. An audio

34、cable (10 feet or less) should be connected from the left channel tape (or low) output of the tuner to the left or Channel A tuner (sometimes called high level) input of the tape recorder. Follow the same procedure for the right channel. (350,- LT-110, 310, and 4312 se- ries) A ste1eo tape output is

35、 avail- able on the front panel for use ivith TAPE portable tape machines. A special TO THE FM ANTENNA coaxial, dual channel shielded cable is needed for this output. This cable is usually p rovided with the tape recorder, or can be obtained from you1 dealer. This output can also be used to connect

36、to a pair of high ill,pedance stereo headphones. An FM dipole antenna is supplied with the unit. In strong signal areas this should be more than adequate to pull in most of the FM stations available. Antenna connections are made to the termjnal strip marked Antenna located on the back panel. The dip

37、ole leads are connected to the screws marked G and FM-300 ohms respec- CONNECTION OF FOLDED DIPOLE ANTENNA tively as shown above. The dipole should then be opened to a full T shape and positioned to give the strongest signal possible on the tuning indicator or meter on the front of the tuner. Tuners

38、 using an indicator tube show a strong signal when the dark strip in the center shrinks to its narrowest. Tuners with meters show a strong signal when the pointer is at its highest reading. The dipole may have to be shifted slightly when trying to receive stations at different directions from the li

39、stener. A compromise posi- tion can usually be found that will work best for most of the stations desired. Generally, the higher the dipole can be placed, the stronger the signal. If you wish to place the dipole further away from the tuner than its present lead length permits, you can purchase from

40、your dealer additional lengths of 300 ohm antenna wire to connect between the dipole and the tuner antenna terminals. In fringe areas, or areas of high interference, an external direc- tional antenna may be necessary. This is particularly true ,vith multi- plex stereo reception. Reflections from hil

41、ls or ne.arby tall buildings can cause annoying distortion. There are many fine yagi FM an- tennas available which will provide strong signal and reduce interfer- ence, thus enhancing the range of the tuner. The remarkable sensitiv- ity of your Scott tuner, vhen com- bined with a good antenna, Viii

42、per- mit you to receive an astonishing number of distant FM stations, either monophonically or in stereo. In areas of extremely high noise, such as a busy high,vay, the following system is suggested: Mount a yagi antenna (either single or stacked) a l some point as far removed from the source of the

43、 disturbance as possible. Con- nect a 300 ohm to 72 ohm transformer on the mast, and run 72 ohm shielded antenna lead-in Vire to the tuner. The lead-in should not be more than 50 feet in length, if possible. Since the yagi antenna is extremely directional, it is important that it be positioned for t

44、he best reception of desired stations. In areas where stations are avail- able in diverse directions, an antenna rotator is suggested. TO AN AM AN TEN NA (333 SER JES) On the top rear of your 333 youll find an AM loop antenna. This will provide a fair amount of signal anti ,viii permit you lo listen

45、 to most local AM stations clearly. However, your Al1 reception can be tremendously improved by doing any of the follo,ving: 1. Take the AC line cord and ,vrap it around the loop antenna several times before connecting to an AC outlet. 2. Take one of the speaker wires from your amplifier and wrap it

46、 around the loop antenna several times before re-connecting it to the amplifier. E ,. I Xu!rna uAM,. 3. Take the FM antenna lead and wrap it around the loop an- tenna several times before re-connecting it to the FM terminals. 4. Unscrew the loop antenna from the chassis and move it away from the tun

47、er. Try setting it in different positions and by looking at the meter find the one position that gives a stronger signal. 5. Disconnect the strap from the AM to the External screw terminal on the back. Connect a long single strand of lamp or bell wire to the External screw. Run the other end of this

48、 long piece of wire to some point outside the house, preferal,ly on or near the roof. When trying any of these suggestions, use the tuning n1eter on the front panel to judge whatever improvement has been made in signal strength. TO AN AC OUTLET The power cord should be plugged into any 106 to 125 vo

49、lt, 60 to 60 cycle AC source. Do NOT use ,vith a DC outlet. You can plug the power cord into a switched auxiliary AC outlet on your amplifier. When the amplifier is turned on it will turn the tuner on at the same time. 6 7 USING YOUR NEW SCOTT TUNER TURNING YOUR TUNER ON If you connect your AC line cord to an auxiliary switched outlet SELECTOR MON00 su. CH. F11.rER &N FUNCTION POWER OFF ON on your amplifier, the tuner can be left in