Eico-HF81-int-sm维修电路原理图.pdf

RadioFans.CN 收音机爱 好者资料库 general description MODEL Hf - DUAL 14 WATT HI- STEREO AMP - PREAMP GENERAL The EICO Model HF-81 is a complete high fidelity stereo- phonic control center and a pair of 14watt amplifiers, all on one chassis. With it you can select preamplify, and control accurately any stereophonic source (tape, discs, or broadcasts) and feed it through the self-contained dual 14 watt amplifiers to a stereo pair of speaker systems. When you playa monophonic source, the 14 watts available per channe I adds up to a total of 28 watts for your two speaker systems. If you desire, both amplifiers can be connected in parallel and driven byone preamp I ifier-control section whi Ie the other preampl ifier-control section is free to drive an 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 to dispense with cabinetry if desired. FEATURES 1. Separate low level input in each channel for mag. phono, tape head, and microphone. Circuitry carefully designed to provide the high gain required by tape heads and high quality, low output mag. cartridges without hum and noise problems. A front panel switch permits choice of the proper NARTS tape head equalization for either 7 1/2 ght I1d 1958 Electronic Instrument Company, Inc. RadioFans.CN 收音机爱 好者资料库 SPECIFICATIONS * Output Power:28 watts continuous; 56 watts peak. 1M Distortion (60c 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 at less than 1% 50c to 5kc; 8.4 watts at less than 2% at 20c. Transient Response: excellent square wave reproduction (4usec rise time) negligible ringing, rapid settl ing on 10kc square wave. Transient Distortion (60cps tone burst)less than 1% at fu II power. Inverse Feedback: 20db Stability Margin:12db Damping Factor: above 8,20 cps - 15 kc. Sensitivity (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 tape head - 51 db; mic - 57 db; tuners, aux- iI iaries - 75 db. Tone Control Range: :I:15db at 50c and 10kc. Speaker 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 for two channels combined; divide power output figures by two for specifications of each channel alone. Design property specifications refer, of course, to either or both channels. * Measured with tone controls set flat, LEVEL control maximum, and FOCUS control set for maximum gain in channe I checked. RadioFans.CN 收音机爱 好者资料库 mechanical installation GENERAL a) HEAT DISSIPATION (VENTILATION): In common with other electronic equipment, the 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 life will be greatly curtailed. It is useful to understand the process of convection where- by heat is removed in judging the suitability of a location. Air heated by the heat-producing elements expands and rises; cool air is drawn from beneath to take the place of the heated air. In this manner, a stream of air is set in motion which continually removes heat from the ampli- fier. (In particular, we are mainly concerned with the major heat-producing elements; the four EL84 output tubes and the two EZSl rectifier tubes.) If there is any impedi- ment to or constriction of the airflow, the essential process of heat removal will be adversely affected. Adequate ventilation will be provided if the amplifier is installed in an open-back console provided that the top of the amplifier is spaced at least two inches below any shelf mounted above it. If the cabinet is enclosed at the rear, provide several large holes or slots as low down and as high up in the cabinet back as possible. As an alter- nate, holes may be provided in the sides, bottom, or top of the cabinet. The important thing to remember is that effective 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 be situated on an open surface or on a shelf of a boakcase Four rubber feet are also provided so that the amplifier will not mar the surface of furniture on which it is placed. b) EASY ACCESS TO CONTROLS: Mount the amplifier at a height which will permit easy manipulation of the con- trols. Tuner controls should be located nearby. c) ACCESSIBILITY TO PARTS:. Tubes are the most fre- quently replaced items in electronic equipment. If the amplifier is installed in a console, sufficient space should be alloted to reach and remove any tube in the amplifier. Furthermore, input and output terminals of the ampl ifier should be accessible to permit easy interchanging 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 the back of the console in which the amplifier is installed, arrange them so they will not interfere with access to the amplifier. d) ACOUSTICAL ISOLATION: If amplifier and speaker are installed in the same cabinet (not recommended) pro- vide sufficient separation to minimize mechanical speaker vibration reaching the amplifier. The minimum separation is about one foat. CONSOLE MOUNTING a) 0 erationsonconsolefront anel reliminar to am li- fier mounting: Tape the panel template provided to the face of the console so that the top of the mounting sur- face line on the template is level with the top of the amplifier mounting shelf. Note: When shelf is not avail- able, tape the template atanyconvenientspot on the face of the console. (2) Use an awl or a nai I to pierce the centers of the four extreme outer holes for mounting the control plate, to transfer their locations to the console panel beneath. (3) Trace out the rectangular cutout with an awl or nail and then pierce the centers of the four 1/2 holes) one in each corner of the cutout. (4) Remove the panel template. (5) Drill the four 1/2 holes in the con- sole panel, one in each corner of the rectangular cutout area. Cut out the rectangular piece with a keyhole sawl using the four 1/2 holes as starting holes. b) Am lifier mounting in console: (1) Pull off the control knobs. 2 Remove the four screws that fasten the bezel to the side pieces and remove the bezel. (3) Remove the two screws and nuts that fasten the control plate to the bezel. 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 rubber feet have been inserted irwhe bottom plate, remove them. (They may be pried out with a thin screwdriver.) (6) Place the unit - on the mounting shelf and slide it forward until the slide switch sl,lpport bracket is up against the panel and the slide switch accessible from the front; the control shafts should be approximately centered in the corresponding holes in the control plate. (7) With a sharp penci!l draw the outline of the side and rear bottom edges on the chassis shelf. As the bottom plate falls short of the full width by 3/16 on each side, draw new side edge lines 3/16 in- side the original side edge lines. (S) Now remove the knobs and take the chassis off the shelf. (9) Remove the 6screws which fasten the bottom plate to the chassis. (10) Place the bottom plate exactly in the outl ine drawn on the shelf and mark the position of the center hole on the left side and the center hole on the right side. (11) Remove the bottom plate and dril! each of the marked holes on the shelf to a diameter of 1/4(12) Refasten the bottom plate to the chassislwiththefourof the six#8x3/Sscrews previously removed, using the two holes at the rear and the two holes at the front of the chassis. (13) Replace the chassis on the shelfl positioning it exactly in the outline previously drawn, and restore the knobs. This time make sure that the indicator dot on each knob agrees with the control position. (14) From the bottom side of the shelf insert a #S xl screw, with a 1/2 flat washer against the head, through both the left and right side center holes. These screws engage the stamped nut over each hole on the chassis flange and when tightened secure the chassis to the shelf. RadioFans.CN 收音机爱 好者资料库 electrical installation The HF-81 can be used in two ways for a stereophonic system. In all cases, plug monophonic sources and one track of monophonic/stereophonic sources in the channel 1 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 phono refers to playback of a monophonic recording with a stereo- phonic cartridge. CH. 32 16 8 CH. 32 (J) (J) (f) (j) (J) (j) (j) TO MATCHING TAP TO MATCHING TAP a) INTERNAL POWER AMPLIFIERS OPERATED SEPARATE- LY, EACH DRIVING ONE SPEAKER OF A STEREO PAIR. This arrangement is used when there is no other amplifier the user desires to include in the system. The SERVICE SEL. sl ide switch on top of the chassis must be set to SEP- arate. Signal connections are all internal, so only the speaker connection need to shown (Fig. la, rear chassis view). The internal arrangement ion in the HF-81 at each of the positions of the FUNCTION selector are shown in Figs. Ib, lc, Id, Ie, If, and 19, as an aid to understand- ing the operation with this arrangement. SPKR.SPKR. FIG. la. SPEAKER CONNECTIONS FIG. CHECK AMPL. 1 CH.I LOW LEVEL INPUTS CH. 1 HIGH CH. 1 LEVEL INPUTS TAPE OUT IPREAMP CH.CH. POWER AMP SPEAKER CH. CH. FIG. CHECK AMPL. 2 CH.2 LOW LEVEL INPUTS PREAMP CH.CH. CH.2HIGH CH. LEVEL INPUTS T APE OUT POWER AMP SPEAKER CH. CH. CH. 1 HIGH LEVEL INPUTS CH. TAPE OUT CH. 1 LOW LEVEL INPUTS SPEAKER CH. FIG. Id STEREO NORMAL CH.2 LOW LEVEL INPUTS SERVICE SEL. :P SEP . I PO ;. AMP R CH.2 HIGH CH. LEVEL INPUTS TAPE OUT CH.1 HIGH LEVEL INPUTS CH. TAPE OUT CH.2 LOW LEVEL INPUTS SPEAKER CH. CH. 1 LOW LEVEL INPUTS FIG. Ie STEREO REVERSE SEP SPEAKER CH. CH. 2 HIGH LEVEL INPUTS CH. TAPE OUT RadioFans.CN 收音机爱 好者资料库 b) INTERNAL POWER AMPLIFIERS COMBINED (TIED TOGETHER AT THE INPUTS AND PARALLELED AT THE OUTPUTS) TO DRIVE ONE SPEAKER OF A STEREO PAIR. This arrangement is employedwhen the useralready has a high quality amplifier (usually 20watts or more if it is to be worthwhile) which he desire to include in the system. The preamp-tone control combination including the reg- ular CHI tone control feeds the combined internal power amplifiers; the preamp-tone control combination including the regular CH2 tone control feeds out through the CH2 TAPE OUT jack to an external power amplifier. The SER- VICE SELECTOR switch on the chassis must be set at the COMbined position for this service in order to disconnect the input of the CH2 power amplifier from the output of the CH2 tone control and connects it instead to the input of the CHl power amplifier, The CHI and CH2 power amplifiers are paralleled at the outputs, as shown, by an external jumper connected between corresponding speaker connection taps, The external signal connection and the speaker connections are shown in Fig, 2a. The internal arrangements in the HF-81 at each of the positions of the FUNCTION selector are shown in Figs. 2b, 2c, 2d, 2e, , and 2g, as an aid to understanding the operation with this arrangement. CH. 1 LOW LEVEL INPUTS FIG. MONOPHONIC TUNER, TAPE, TV CH. 1 LOW LEVEL INPUTS FIG. Ig MONOPHONIC PHONO CH.2 LOW LEVEL INPUTS CH. 1 LOW LEVEL INPUTS FIG. CHECK AMPL. CH. 1 HIGH LEVEL INPUTS CH. TAPE OUT SEP CH. TAPE OUT CH. 1 HIGH LEVEL INPUTS CH. T APE OUT SERVICE SEL SEP:MP CH.2HIGH CH. LEVEL INPUTS T APE OUT TAPE OUTCH. - (f) . I :! I :Q it I a I I EXTRNABASIC - POWER AMPLIFIER i I 1_- .INPUT SPEAKER CH 1 SPEAKER CH. SPEAKER CH. SPEAKER CH. CH. * On integrated amplifiers HF20, HF32 feed into TAPE OUTPUT lack; on HF521 feed into ELECTRONIC CROSS- OVER INPUT jack, after severing connection between ELECTRONIC CROSSOVER IN and OUT jacks. FIG. 2a. SPEAKER for RI = 50KQ, use Rs = 1 OOKQ; for RI : 33KQ, use Rs = 50KQ; for RI = 25KQ, use Rs = 33KQ. SPEAKER CH. * NOTE: All ceramic cartridge manufacturers have devel- oped simple networks which when connected the outputs of their cartridges result in a characteristic identical to that of magnetic cartridges. By interposing the recom- mended adaptor for the particular ceramic cartridge be- tween the cartridge outputs and the MAG. PHONO in- puts of the ampl ifjer, it is possible to use the MAG. PHONO inputs for the ceramic cartridge with excellent results. Adaptor networks are given in the literature for the par- ticular ceramic cartridge and can be built on a terminal strip mounted on the underside of the phonograph base, or may be available in convenient component form from the cartridge manufacturer. Stereophonic crystal cartridges (Ronette Binofluid II OV and BF40) can be connected di- rectly to auxiliary high level inputs. 2) TAPE HEAD 1, TAPE HEAD 2: These inputs are in- tended for direct connection to the two outputs of a stereo tape playback head. A front panel slide switch permits choice of NARTB tape head equalization either for71/2 ( the two speaker systems must be in phase and placed near one another for this adJustment. Next, procede y TO MAG. INPUT ,- TO MAG. INPUT 2 mentioned sources to the correspondmg amplifier input jack. Unless the source has a low-impedance output such as a cathode follower (with which up to 50ft. of cable can be used), use the shortest possible connection and low - capacity shielded cable (cable having as low as 25mmfd capacitance per foot is available). d) TAPE OUTPUT 1, TAPE OUTPUT 2: When no external amplifier is used in the system, both these outputs are available for feeding out to a stereo recorder. When an external power ampl ifier is used in the system, TAPE OUT- PUT 2 is used to feed out to the external power amplifier. If it is desired to do stereo recording under the latter conditions, construct a device such as shown in Fig. 4. Use low capacity shielded cable for connections. TO INPUT 2 OF STEREO RECORDER TO EXTERNAL POWER AMPLIFIER 6 , follows: With your ear held close to the speakers, insert the amplifier power plug into the wall outlet and listen to the hum level. Now pull out the plug and re-insert it with the prongs reversed. Choose the prong position with the least hum. Now connect the tuner input connector to the amplifier input jack, and with the tuner set between stations and the tuner volume control set at a minimum, do the same with the power plug of the tuner; use either the 117VAC receptacle on the HF-81 or one receptacle of a cube tap inserted in the 117V AC receptacle on the HF