Eico-HF81-int-sm维修电路原理图.pdf

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1、RadioFans.CN 收音机爱 好者资料库general descriptionMODEL Hf - DUAL 14 WATT HI- STEREO AMP - PREAMPGENERALThe EICO Model HF-81 is a complete high fidelity stereo-phonic control center and a pair of 14watt amplifiers, allon one chassis. With it you can select preamplify, andcontrol accurately any stereophonic

2、source (tape, discs, orbroadcasts) and feed it through the self-contained dual 14watt amplifiers to a stereo pair of speaker systems. Whenyou playa monophonic source, the 14 watts available perchanne I adds up to a total of 28 watts for your two speakersystems. If you desire, both amplifiers can be

3、connectedin parallel and driven byone preamp I ifier-control sectionwhi Ie the other preampl ifier-control section is free to drivean external power amplifier. In this way your old ampli-fier can be put to use in a stereophonic system. Construc-tion is of the Iow silhouette type that permits you tod

4、ispense with cabinetry if desired.FEATURES1. Separate low level input in each channel for mag.phono, tape head, and microphone. Circuitry carefullydesigned to provide the high gain required by tape headsand high quality, low output mag. cartridges without humand noise problems. A front panel switch

5、permits choiceof the proper NARTS tape head equalization for either7 1/2 & 15 or 3 3/4ips tape speeds.2. Separate high level inputs for AM, FM, and FMMultiplex. Also two auxiliary A inputs (one in eachchannel) and two auxil iary B inputs (one in each channel).Input Selector switch on front panel has

6、 positions for feed-ing FM tuner output to one channel and AM tuner toother, or FM tuner to one channel and FM Multiplexadapter output to other.3. May be used as either two independent amplifier-preamplifiers,or one preamplifier-control section may beset free to operate an external power amplifier a

7、nd theother preampl ifjer-control section used to drive both in-ternal power ampl ifiers connected in parallel at thespeaker connection terminals. A top - of-chassis sl ideswitch permits choice of operation.4. Ganged level controls and a separate focus (balance)control.5. Independent full-range bass

8、 and treble tone controlsin each channel. Tone controls of the low distortionvariable cross-over feedback type.6. Identical Williamson type, push-pull EL84power am-plifiers with high quality output transformers.7. Hum balance control, panel-mounted fuse, pi lot lamp,convenience outlets.8. EICO low s

9、ilhouette construction employing hori-zontal chassis for proper layout and component separation.Easy console installation, if desired, with complete shield-ing and adapatability to any panel thickness.Copy,;ght I1d 1958 Electronic Instrument Company, Inc.RadioFans.CN 收音机爱 好者资料库SPECIFICATIONS *Output

10、 Power:28 watts continuous; 56 watts peak.1M Distortion (60c &7kc at 4: : 2% at 28 watts; 0.at 10 watts.Frequency Response:(2w):I:O. 5db 10c to 1O0kc.HarmonicDistortion:16 watts at less than 1% 30c to lOkc;20 watts at I ess than 1 % 40 c to 10 kc; 28 watts atless than 1% 50c to 5kc; 8.4 watts at les

11、s than2% at 20c.Transient Response: excellent square wave reproduction(4usec rise time) negligible ringing, rapid settl ingon 10kc square wave.Transient Distortion (60cps tone burst)less than 1% atfu II power.Inverse Feedback: 20dbStability Margin:12dbDamping Factor: above 8,20 cps - 15 kc.Sensitivi

12、ty (input for rated output):mag. phono 4mv;tape head 7.5 ips - 2 mv; tape head 3.75 ips 5mv; mic - 6mv; tuners, auxiliaries - 0.5V.* Hum & Noise Level (below rated output):mag. phono 60db; tape head - 51 db; mic - 57 db; tuners, aux-iI iaries - 75 db.Tone Control Range: :I:15db at 50c and 10kc.Speak

13、er Connections: 48, and 16 ohms.Tubes: 4 - ECC83/12AX7, 2 - ECC82/12AU7, 4- EL84,2 - EZ81.Size:15 wide, 4 3/4 high, 10 1/2 deep.Weight: 241bs.* Where power output is involved, figures are given fortwo channels combined; divide power output figures bytwo for specifications of each channel alone. Desi

14、gnproperty specifications refer, of course, to either or bothchannels.* Measured with tone controls set flat, LEVEL controlmaximum, and FOCUS control set for maximum gain inchanne I checked.mechanical installationGENERALa) HEAT DISSIPATION (VENTILATION): In common withother electronic equipment, the

15、 HF-Sl produces consider-able heat in normal operation. Unless continuous and ade-quate air flow is obtained around the heat producing ele-ments, these elements will over-heat and their useful lifewill be greatly curtailed.It is useful to understand the process of convection where-by heat is removed

16、 in judging the suitability of a location.Air heated by the heat-producing elements expands andrises; cool air is drawn from beneath to take the place ofthe heated air. In this manner, a stream of air is set inmotion which continually removes heat from the ampli-fier. (In particular, we are mainly c

17、oncerned with themajor heat-producing elements; the four EL84 output tubesand the two EZSl rectifier tubes.) If there is any impedi-ment to or constriction of the airflow, the essential processof heat removal will be adversely affected.Adequate ventilation will be provided if the amplifier isinstall

18、ed in an open-back console provided that the topof the amplifier is spaced at least two inches below anyshelf mounted above it. If the cabinet is enclosed at therear, provide several large holes or slots as low down andas high up in the cabinet back as possible. As an alter-nate, holes may be provid

19、ed in the sides, bottom, or topof the cabinet. The important thing to remember is thateffective ventilation requires provision for cool air to en-ter at the bottom and hot air to leave at the top.If the amplifier is not installed in a console, it may besituated on an open surface or on a shelf of a

20、boakcaseFour rubber feet are also provided so that the amplifier willnot mar the surface of furniture on which it is placed.b) EASY ACCESS TO CONTROLS: Mount the amplifierat a height which will permit easy manipulation of the con-trols. Tuner controls should be located nearby.c) ACCESSIBILITY TO PAR

21、TS:. Tubes are the most fre-quently replaced items in electronic equipment. If theamplifier is installed in a console, sufficient space shouldbe alloted to reach and remove any tube in the amplifier.Furthermore, input and output terminals of the ampl ifiershould be accessible to permit easy intercha

22、nging of sys-tem components for comparison, and connection or dis-connection of a portable tape recorder which is stored a-way when not in use. If antennas are strung around theback of the console in which the amplifier is installed,arrange them so they will not interfere with access to theamplifier

23、.d) ACOUSTICAL ISOLATION: If amplifier and speakerare installed in the same cabinet (not recommended) pro-vide sufficient separation to minimize mechanical speakervibration reaching the amplifier. The minimum separationis about one foat.CONSOLE MOUNTINGa) 0 erationsonconsolefront anel reliminar to a

24、m li-fier mounting: Tape the panel template provided tothe face of the console so that the top of the mounting sur-face line on the template is level with the top of theamplifier mounting shelf. Note: When shelf is not avail-able, tape the template atanyconvenientspot on the faceof the console. (2)

25、Use an awl or a nai I to pierce thecenters of the four extreme outer holes for mounting thecontrol plate, to transfer their locations to the consolepanel beneath. (3) Trace out the rectangular cutout withan awl or nail and then pierce the centers of the four 1/2holes) one in each corner of the cutou

26、t. (4) Remove thepanel template. (5) Drill the four 1/2 holes in the con-sole panel, one in each corner of the rectangular cutoutarea. Cut out the rectangular piece with a keyhole sawlusing the four 1/2 holes as starting holes.b) Am lifier mounting in console: (1) Pull off the controlknobs. 2 Remove

27、 the four screws that fasten the bezelto the side pieces and remove the bezel. (3) Remove thetwo screws and nuts that fasten the control plate to thebezel. The bezel is not used in console mounting. )Fasten the control plate to the console panel with the two#4x3/S wood screws supplied. (5) If the ru

28、bber feet havebeen inserted irwhe bottom plate, remove them. (They maybe pried out with a thin screwdriver.) (6) Place the unit -on the mounting shelf and slide it forward until the slideswitch sl,lpport bracket is up against the panel and theslide switch accessible from the front; the control shaft

29、sshould be approximately centered in the correspondingholes in the control plate. (7) With a sharp penci!l drawthe outline of the side and rear bottom edges on the chassisshelf. As the bottom plate falls short of the full width by3/16 on each side, draw new side edge lines 3/16 in-side the original

30、side edge lines. (S) Now remove theknobs and take the chassis off the shelf. (9) Remove the6screws which fasten the bottom plate to the chassis. (10)Place the bottom plate exactly in the outl ine drawn on theshelf and mark the position of the center hole on the leftside and the center hole on the ri

31、ght side. (11) Removethe bottom plate and dril! each of the marked holes on theshelf to a diameter of 1/4(12) Refasten the bottomplate to the chassislwiththefourof the six#8x3/Sscrewspreviously removed, using the two holes at the rear and thetwo holes at the front of the chassis. (13) Replace thecha

32、ssis on the shelfl positioning it exactly in the outlinepreviously drawn, and restore the knobs. This time makesure that the indicator dot on each knob agrees with thecontrol position. (14) From the bottom side of the shelfinsert a #S xl screw, with a 1/2 flat washer againstthe head, through both th

33、e left and right side center holes.These screws engage the stamped nut over each hole onthe chassis flange and when tightened secure the chassisto the shelf.electrical installationThe HF-81 can be used in two ways for a stereophonicsystem. In all cases, plug monophonic sources and onetrack of monoph

34、onic/stereophonic sources in the channel1 inputs; plug the other track of stereo sources in the chan-nel 2 inputs. It is assumed in what follows that a stereo-phonic phono cartridge is being used. Monophonic phonorefers to playback of a monophonic recording with a stereo-phonic cartridge.CH.32 16 8

35、CH.32 (J) (J) (f) (j) (J) (j) (j)TO MATCHINGTAPTO MATCHINGTAPa) INTERNAL POWER AMPLIFIERS OPERATED SEPARATE-LY, EACH DRIVING ONE SPEAKER OF A STEREO PAIR.This arrangement is used when there is no other amplifierthe user desires to include in the system. The SERVICESEL. sl ide switch on top of the ch

36、assis must be set to SEP-arate. Signal connections are all internal, so only thespeaker connection need to shown (Fig. la, rear chassisview). The internal arrangement ion in the HF-81 at eachof the positions of the FUNCTION selector are shown inFigs. Ib, lc, Id, Ie, If, and 19, as an aid to understa

37、nd-ing the operation with this arrangement.SPKR.SPKR.FIG. la. SPEAKER CONNECTIONSFIG.CHECK AMPL. 1CH.I LOW LEVEL INPUTSCH. 1 HIGH CH. 1LEVEL INPUTS TAPE OUTIPREAMPCH.CH.POWER AMP SPEAKERCH.CH.FIG.CHECK AMPL. 2CH.2 LOW LEVEL INPUTSPREAMPCH.CH.CH.2HIGH CH.LEVEL INPUTS T APE OUTPOWER AMP SPEAKERCH.CH.C

38、H. 1 HIGHLEVEL INPUTSCH.TAPE OUTCH. 1 LOWLEVEL INPUTSSPEAKERCH.FIG. IdSTEREO NORMALCH.2 LOW LEVEL INPUTSSERVICE SEL.:P SEP .I PO;.AMP RCH.2 HIGH CH.LEVEL INPUTS TAPE OUTCH.1 HIGHLEVEL INPUTSCH.TAPE OUTCH.2 LOWLEVEL INPUTSSPEAKERCH.CH. 1 LOWLEVEL INPUTSFIG. IeSTEREO REVERSESEPSPEAKERCH.CH. 2 HIGHLEVE

39、L INPUTSCH.TAPE OUTb) INTERNAL POWER AMPLIFIERS COMBINED (TIEDTOGETHER AT THE INPUTS AND PARALLELED AT THEOUTPUTS) TO DRIVE ONE SPEAKER OF A STEREO PAIR.This arrangement is employedwhen the useralready has ahigh quality amplifier (usually 20watts or more if it is tobe worthwhile) which he desire to

40、include in the system.The preamp-tone control combination including the reg-ular CHI tone control feeds the combined internal poweramplifiers; the preamp-tone control combination includingthe regular CH2 tone control feeds out through the CH2TAPE OUT jack to an external power amplifier. The SER-VICE

41、 SELECTOR switch on the chassis must be set at theCOMbined position for this service in order to disconnectthe input of the CH2 power amplifier from the output ofthe CH2 tone control and connects it instead to the inputof the CHl power amplifier, The CHI and CH2 poweramplifiers are paralleled at the

42、 outputs, as shown, by anexternal jumper connected between corresponding speakerconnection taps, The external signal connection and thespeaker connections are shown in Fig, 2a. The internalarrangements in the HF-81 at each of the positions of theFUNCTION selector are shown in Figs. 2b, 2c, 2d, 2e, a

43、nd 2g, as an aid to understanding the operation withthis arrangement.CH. 1 LOWLEVEL INPUTSFIG.MONOPHONIC TUNER,TAPE, TVCH. 1 LOWLEVEL INPUTSFIG. IgMONOPHONIC PHONOCH.2 LOWLEVEL INPUTSCH. 1 LOWLEVEL INPUTSFIG.CHECK AMPL. CH. 1 HIGHLEVEL INPUTSCH.TAPE OUTSEPCH.TAPE OUTCH. 1 HIGHLEVEL INPUTSCH.T APE OU

44、TSERVICE SELSEP:MPCH.2HIGH CH.LEVEL INPUTS T APE OUTTAPEOUTCH.-(f). I:! I:Q it Ia I I EXTRNABASIC- POWER AMPLIFIER i I1_-.INPUTSPEAKERCH 1SPEAKERCH.SPEAKERCH.SPEAKERCH.CH.* On integrated amplifiers HF20, HF32 feed into TAPEOUTPUT lack; on HF521 feed into ELECTRONIC CROSS-OVER INPUT jack, after sever

45、ing connection betweenELECTRONIC CROSSOVER IN and OUT jacks.FIG. 2a. SPEAKER & EXTERNALSIGNAL CONNECTIONs.CH. 1 HIGHLEVEL INPUTSCH.TAPE OUTSPEAKERCH.FIG.CHECK AMPL. 2FIG.STEREO NORMALFIG.STEREO REVERSEFIG.MONOPHONIC TUNER,T APE, CH.2 LOWLEVEL INPUTSCH. I LOWLEVEL INPUTSCH.2 LOWLEVEL INPUTSCH. I LOWL

46、EVEL INPUTSCH.2 LOWLEVEL INPUTSCH. I LOWLEVEL INPUTSCH.2 HIGHLEVEL INPUTSCH.TAPE OUTCH. I HIGHLEVEL INPUTSCH.TAPE OUTCH.2 HIGHLEVEL INPUTSCH.TAPE OUTCH.2 HIGHLEVEL INPUTSCH.TAPE OUTCH. I HIGHLEVEL INPUTSCH.TAPE OUTSPEAKERCH.SPEAKERCH.SPEAKERCH.SPEAKERCH.SPEAKERCH.SPEAKERCH.SPEAKERCH.CH.l HIGHLEVEL I

47、NPUTSCH.T APE OUTCH. 1 LOWLEVEL INPUTSFIG.MONOPHONIC PHONOSPEAKERCH.CH.2 LOWLEVEL INPUTSCOMCH.2 HIGHLEVEL INPUTSCH.T APE OUTc) INPUTS: There are identical pairs of MAG. PHONO,TAPE HEADMICROPHONE, AUXILIARY A, and AUX-ILIARY B inputs -one of each pair in channell and chan-nel 2 - and each is identifi

48、ed accordingly by the suffix1 or 2. The MAG. PHONO, TAPE HEAD, and MICRO-PHONE pairs of inputs are all II low level inputs, mean-ing that they all feed through a preamplifier/equalizerstage in either channell or 2. The AUXILIARY A andAUXILIARY Bpairsofinputs arehigh level inputs, mean-ing that they

49、enter either channell or 2 at a point afterthe preampl ifier/equalizer stages. The AM, FM and FM-FM Multiplex inputs are also high level inputs, whichare internally selected in pairs - one for each channel- by the INPUT SEL. switch. At the MONAURAL posi-tion of the FUNCTION SEL., AM only is selected

50、 at theAM-FMposition of the INPUT SEL., and FMonlyis select-ed at the FM - FM MULTI. position of the INPUT SEL.l) MAG. PHONO 1, MAG. PHONO 2: These inputsare intended for the two outputs of a stereo magneti c car-tridge, or for a stereo ceramic cartridge with adaptors.The correct method for wiring a