MODEL HF-81 DUAL 14 WATT HI-FI STEREO AMp·PREAMP general description GENERAL channel) and two auxiliary Binputs (one in each channel). nout Selector switch on front panel has positions for feednpur serecror swiren on rronr panel nas polil I lun::o lUI ."''''... ing FM tuner output to one channel and AM tuner to other, or FM tuner to one channel and FM Multiplex adapter output to other.
SPECIFICATIONS * ** Hum & Noise Level (below rated output): mag. phono - Output Power: 28 watts continuous; 56 watts peak. 60db; tape head - 51 db; mic - 57 db; tuners, auxll iaries - 75 db. 1M Distortion (60c &7kc at 4: 1): 2% at 28 watts; 0.5% at 10 watts. Tone Control Range: ±15db at 50c and 10kc. Frequency Response: (2w):I:O. 5db 10c to lOOkc. Speaker Connections: 4,8, and 16 ohms.
mechanical installation GENERAL CONSOLE MOUNTING a) HEAT DISSIPATION (VENTILATION): In common with other electronic equipment, the HF-81 produces considerable heat in normal operation. Unless continuous and adequate air flow isobtained around the heat producing elements, these elements will over-heat and their useful life will be greatly curtailed.
electrical installation CH.2 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 channel 2 inputs. It is assumed in what follows that a stereophonic phono cartridge is being used . Monophonic phono refers to playback of a monophonic recording with a stereophonic cartridge. 32 16 G 32 TO MATCHING TAP 4 G SPKR.I FIG. 10.
CH.I HIGH LEVEL INPUTS CH.I TAPE OUT 1-_ _ SPEAKER CH.I LOW LEVEL INPUTS CH I FIG.1f MONOPHONIC TUNER, TAPE, TV SEP 1---_ SPEAKER CH.2 CH.2 TAPE OUT CH. I TAPE OUT CH. I HIGH LEVEL INPUTS I--_ _ SPEAKER CH. I LOW LEVEL INPUTS CH. I FIG. 19 MONOPHONIC PHONO CH.2 HIGH LEVEL INPUTS b) INTERNAL POWER AMPLIFIERS COMBINED (TIED TOGETHER AT THE INPUTS AND PARALLELED AT THE OUTPUTS) TO DRIVE ONE SPEAKER OF A STEREO PAIR.
FIG.2c CHECK AMPL. 2 CH.2 LOW LEVEL INPUTS CH.2 HIGH LEVEL INPUTS CH.2 TAPE OUT _ SPEAKER CH.2 CH. I HIGH LEVEL INPUTS CH.I TAPE OUT CH.I LOW LEVEL INPUTS FIG.2d STEREO NORMAL SPEAKER CH.I CH.2 LOW LEVEL INPUTS CH.2 HIGH LEVEL INPUTS CH.2 TAPE OUT _ SPEAKER CH.2 CH.l LOW ... LEVEL INPUTS _ FIG.2e STEREO REVERSE SPEAKER CH.I CH.2 LOW LEVEL INPUTS CH.2 HIGH LEVEL INPUTS CH.2 TAPE OUT I--_--.:SPEAKER CH.2 CH.l HIGH LEVEL INPUTS CH.l LOW LEVEL INPUTS SPEAKER CH.l FIG.
CH.l HIGH LEVEL INPUTS CH.l TAPE OUT CH.l LOW LEVEL INPUTS FIG.2g MONOPHONIC PHONO SPEAKER CH.l CH.2 LOW LEVEL INPUTS CH.2 HIGH LEVEL INPUTS CH.2 TAPE OUT f - - - SPEAKER CH.2 * NOTE: All ceramic cartridge manufacturers have developed simple networks which when connected the outputs of their cartridges result in a characteristic identical to that of magnetic cartridges. By interposing the recommended adaptor for the particular ceramic cartridge between the cartridge outputs and the MAG.
STEREO MAG. CARTRIDGE ~ ~ ~~ -~, - (8- I TO MAG. INPUT 1 B-1 TO MAG. INPUT 2 FIG. 3 5) AUXILIARY B'l, AUXILIARY B2: Same as for AUXILIARY AI, AUXILIARY A2 above. 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 os low as 25mmfd capacitance per foot is available).
operation PRELIMINARY: Be sure all tubes are firmly seated in their sockets and that the tube shields are making good contact with their baSes. As initial adJustments, set these controls as follows: LEVEL at 0, FOCUS at Or both BASS controls at O. Tum the amplifier on by turning the TREBLE 2 control clockwise from AC OFF and set it at zero initially. Also set the TREBLE 1 control at zero.
The plus sign on the right side of the dial indicates that TREBLE CONTROL 1, TREBLE CONTROL 2 (CONCENTRIC): The plus sign on the right side of the dial indicates clockwise rotation from the mid- point (0) of either control that clockwise rotation from the mid-point BASS CONTROL 1, BASS CONTROL 2 (CONCENTRIC): increases (boosts) _bas~ response; the minus sign on the left side indicates that counter- clockwise rotation from the (0) of either control increases (boosts) treble response; the minus sign
CHECKING A TYPICAL TUBE STAGE bass re- inforcement and the other bass cancellation. The connection that gives bass re- inforcement is the in- phase connection and should be used. 1. Check tube. 2. Check plate and cathode resistor. 3. Check coupl ing capacitors for leakage or short. 4. For output stage, check dc Another criterion for the in- phase connection is that of resistance of transformer windings. 5.
TROUBLE- SHOOTING CHART SYMPTOM Amplifier causes power line fuse to blow. Power line fuse blows again with VII & V12 out of their sockets. REMEDY CAUSE Line cord, J16, primary or high voltage Replace or repair. secondary windings of T1 shorted internally or externally (wiring). VI0, or T2 Amplifier causes power line fuse to blow. Power line fuse does not blow again with VII & V12 out of their sockets. VII, V12, C39)' V7, va, V9, Any or all tube filaments not lit. Open tube fil ament.
VOLTAGE AND RESISTANCE CHART TUBE PIN# OPERATING VOLTS AT NO SIGNAL (DC UNLESS NOTED) OPERATING VOLTS AT 14W OUT (DC UNLESS NOTED) SIGNAL VOLTS (1 kc) at 30W OUT FROM POWER) 014 290KO IMO 7KO 0035 290KO 90KO 2KO CC83(12AX7 4&5 OHMS UN IT DISCONNECTED 500 filament (OVDC; 6. 3VAC to pin 9) 500 filament 290KO IMO 7KO ECC83/12AX7 4&5 500 filament (OVDC; 6. 3VAC to pin 9) 290KO 90KO 2KO 500 fi lament 1. 2 ECC82/12AU7 V3, V4 . 1 4&5 500 filament (OVDC; 6. 3VAC to pin 9) 1. 8 1.
EL84/6BQ5 V9, V10 0 6. 7 12. 7 14. . 03 * 4&5 EZ81/6CA4 VII, V12 4&5 filament (OVDC; 6. 3VAC between pins 4 & 5) 335 325 330 320 290 V AC * 29OV AC* 180 340 335 7. 290* filament (340VDC; 6. 3VAC between pins 4 & 5) 290V AC * 290V AC * 290* 340KQ 340KQ 165Q 50 Q 165- 190 Q 330KQ 350Q 45- 55 Q 100KQ 100KQ 45- 55 Q * = 60 cycles All resistance measurements, except those made from pin 3 of Vl1 and V12 (EZ81 rectifier), are made with pin 3 of V11 and V12 grounded.
AUXA SECTION AM-FM AUX B FM-MUL TI PHONO MIC TAPE INPUT SELECTOR 11- 11- SWITCH 2-6- S 1 10- 11- 10- 11- 10- 10- 12 10- 11- 10- 113- 7 4-11 1 -4- 2-4- 3-4- 10- 10- 10- 3-610- 12. 10- 1":12 10- 10- SECTION 10- 10- AMPL. 2 AMPL. 1 10- 9- 1 0- NORMAL 10-11 TUNER AUX. REVERSE PHONO FUNCTION SELECTOR SWITCH 3-4-7 4- 10 1) Entries are numbers of those switch contacts which are connected together by the rotors at the particular position. NC means no connection.
REPLACEMENT PARTS LIST Stock' 20050 23014 23020 22517 22514 22518 22550. 22506 20039 22520 22529 22543 23007 22533 24005 23016 20043 22519 91005 92000 50020 50018 Description Stock' Cl, cop. , paper ~1\T C3, C5, C7, cap., disc., . 025mfd, GMV (25K or 25, OOOmmf) Symbol 25mfd, 200V cop., elec., lOmfd, 6V cap., elec. , 25mfd, 6V 33, C35, 36, 45, 46 C9, Cl1, C13, C15, CI7, 18, 21, CI9, 20, 41, C23, C25, 26, 27, 28 C29, C31, 32, 43, 44 C37 C38, C40 C47, 48 cap., disc., 850mmf, "'10% cap., disc.
Jl1 J12 J13 Jl0 ""1:26 ""C25 -C23 ~C24 -C22 .....C21 --C20 --C19 -CJ8 ,...CJ7 -'J6 -CJ5 ........C14 -c13 ..:.CJ2 - ClI =CIO ~C8 .... C7 ....c6 -c4 ... Cl ';'",,-, C28 200V ~ 6V 6V - 200V "'- C27 C13 ~'4 %10% -:13 %10% - cap., disc., 150mmf, cap., disc. , 225mmf cap., disc., 225mmf %10% _ %10% ' cap., molded, . 1 mfd, ..uJOV, %1O%-"'C48 -Jl cop., disc. , 150mmf %10% %10% GMV %10% 6V 6V GMV cap., elec., 10mfd C29 cop., elec., IOmfd, ,.-C30 cap., elec., 25mfd "'C31 cap.
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to.) -$- TBll XVll XV12 - TB21 TB20 8' '-'. ) !' Fig. 1 XV6 TB3 .
addition to Fig. 1, it will be required to refer to Fig. 6 in the fol- j9 direction in figure 6. chassis and the input jack strip. (Fig. 10). screws, two #4 lockwashers and two hex nuts. Fig. 1. Mount the shown. hex nuts.. Mount a lockwashers, mount one post right terminal strip, TB4. 5 screw terminal board, TBl, as shown. Use two #6- 32 screws, two #6 lockwashers and two #6- 32 hex nuts. Under one of the 8. ( J) 2 hole insulator between the chassis and the jack strip.
PREWIRING OF SELECTOR SWITCH (C) to S 1 B- 7 (S 1). Connect C46 from S IH- 7 (C) to /J) G- (S4). 3/)ft. :Sf) (C). to S 1 G- 1 (S2). Fig. 2. Cut all leads on two 47mmf disc capacitors, C43 and C44, Connect C43 from S 1 B- 12 (S2) to S lC- 12 (S2). Connect C44 from (C) to SlG- l SlG- 5 (Sl) to SlF- 5 (C). 8. ( /Fi9. 2. Cut all leads on two 600mmf disc capacitors, C13 and C14, to 3/4" . Connect C13 frcm SlB- 4 (Sl) to SlC-4 (C). Connect C14 from S 1 F- to 7. Connect;R18 from SlF- l 6. (' Fig.
9. J) Fig. 2. Strip back the outer insulation 1 1/2" from one end of a 10" the shield strands together and IA - 10 (52). Connect a 1" piece of bare wire from S ID- l1 (S2) to S 1 Etwisted shield strands' to S lC- 6 (C). On the other end of the (C). N.) Fig. 2. (S 1), the red lead to S 1 F- l 0 Strip back the insulation 1/4" (Si3) 1 1/2" piece of bare wire from SlC- 6 (S2) to of a 4 1/2" piece of black wire to SlF- 6(C). 7 1/2" piece of 3 conductor shield cable.
(ii) CJI J) ~ (37 R22 R25 R24 Fig.
~g. 3. Mount from the top of the chassis. Use two #4- S4, as shown. Slide potentiometer, R30, as shown. Slide the locating lug on the potentiometer into the small hole 3/8 hex nut. 3/S lockwasher and one (stock# JS04S) 6. (L.) Fig. 3. Mount the dual 250KQ level control potentiometer, R24, R25, Mount the dual concentric bass control Use one 3/8 lockwasher and one 3/S hex nut. 3/8 remove the fuseholder mounted in step 10, on lIon this. page (page 7C), remount the fuseon page 3C.
Top Shield R32 iii 0 eOe eOe ~ICJ~ R33 eOe eOe eOe eOe ffi 10\ 0 0 Fig.
TOP OF CHASSIS WIRING ()('\)/ brown to Jl, 1 (Sl) CY orange to Jl, 2, 3, 3 (Sl) yellow to Jl, 2, 3, black wire from Jl, 2, 3, (V) 6range to J5, 6, 7- 5 (Sl) (originating at S switch, S3. and 51 E- 3 respectively) along the chassis as shown. Push leads tt,rough hole S" in the front panel between the two rotary switches and behind the slide 7. (\ ,,) Fig. 4. Run the twisted white and brown leads two rotary switches and behind the sl ide switch)' S3.
... R32 PCl R33 Fig.
10" piece of grey wire to the swi~ch l)which is mounted on the rear of the dual treble control potentiometers. Connect one end of a 14" piece of black wire to S4- 10 (S 1). Twist the two leads together and push the unsoldered end through hole " V" to the bottom of the connections made previously for PC #3 to R30- 2 (C) and lead #2 to R30- 1 Fig. 5. 1. ( 5. 5. of brown wire to R33- 6 (C). (C). (C) 5.
XV12 TB6 XVll ;:; TB 10 XV5 XV7 R64 -$- TB7 LCD XI1 J16 TB9 TB8 XV3 TB21 J 1415 TB4 XV6 XV8 TBll TB1 TB3 TB19 TB20 XV4 TB2 TB 18 TB5 T B'l5 XV10 J8910 ,I TB 12 XV1 C:37 TB 14 XV9 TB17 XV2 TB13 Fig. 6 J1112. J.
I. 6. F'om n, connect one g'oon leod to (C). the powe' t,on,ro,mer, (C) and the other green lead to R64- 3 (\!) Fig. . 6. Connect one end of a 4 1/2" piece of brown wire to XV7- (C) and the other ~I brown and yellow wires from hole " iFf,. 6. Connect 0 1/2" p; ec. 01 b"'e w; ,. 11. J) Fig. 6. Connect" one end of a 5" piece of yellow wi ~e to XVlO-4 (S2) and one end of a 6" piece of yellow wire to XVS-4 (S2). Twist the wires and run along the chassis as shown.
XVll C38 Jl6 -$- Fig.
1. Fig. 7. From the power transformer, Tl, connect the red- yellow and (IJ) Fig. 7. From the power transformer , Tl, twist the two red leads and d lead to XVll- 7 (C). F,g. 7. Run the piece of spaghetti. Connect one lead to XF1- 1 (S2) C40, to V) Fig. 7. 1). Connect the 350Q, 10 watt resistor , R63, from TB6- 1 (C) Tl, to the black lead (near- 14. (\ hi9' 7. Connect a 6" piece of orange wire from TB6- 2 (S3) to XV7- 9(C). will be connected later.
R25 TB8 TB21 XV7 R57 C29 TB1 J 14 1 5 -$- Fig.
(d) Fig. 8. Cut the negative (-) lead on the 30mfd electrolytic capacitor, (C), the green lead to TB1- 3 U) Fig. 8. Connect a 3 1/2" piece of green wire from XVI 0- 8 (C) to Fig. 8. Cut both leads on a 1650, 5 watt resistor)' R56, to 3/4" (C)r Fig. 8. From the output transformer, T3, connect the yellow lead to the green lead to TB2- 3 (S 1), the brown lead to TB2- 2 (S 1), the (~f (\1 (J) and the inner conductor to TB21- 2 (C). Fig. 8. Connect a 3 1/2" piece of orange wire from TB9-2 (C) 12.
C17 (21 R39 -I' '/' .., \. --:\ TB20 ~" -c . Io -1:: I' fi' ~ 5"""""" ?J", l1'\~ ~ ~,L\. ~:::- ~i.l: "it".-. (9FJ 2 - c~ 0 "';' ~~ !:51$ I 4- \ ~~~~~ , ", 'Ut ,'~ ,,1 "dJ:;!L. ff: ~U t"' ,\1 t! Q: --'c l"r' 7. - R. ) ~ i- " d2; ~dOl , o- ~~c~ c- ~:i \..' ~ ~ Hi' -V I.~L; 7.""""" 'Ii -"". -I- Y\ -~:,r v:' (1?r C 1 i~ts:~ "t\ i1); ~I ----.U /h rtO1 p= IIJ/i) I!iJI!J. 1!iJ/fiJ l!f\!HJ :w~u;r Fig. 9 r---.
9. (vi Fig. disc capacitors, C31 and piece of spaghetti. ,or) (S3) to 184 (S3). Each lead is to be covered with a 1/2" to XV8- 2(Sl). XV8-6 resistor from XV7-8(C)toXV7- 2 (Sl). ConXV1Q;.. 2 (S 1) Connect R52 from XV9- 8 (C) to Conne~t R53 Connect R55 from Connect a 3" piece of grey wire from TB20- 2 (C) toXV9- 8 (S2). 13. Fig 9. Cut (S3). Connect C36 from XV6- 3(C) to TB19-1 (S3). all leads on the two 100KO (brown, black, yellow)' gold) from XY6-1 (C) to TB20- 2 12. (\; Fig. 9.
~, ~(~~ ~~ . ' '" ~" ~ -~ . i&L 1:' L/ R28- C 16 T B 8 C1 R29 R IJ:~ 1)(\r:J fro)j ~ rv' V, ~"U" JSl) ~:D J-- .-r . O Ft. ;;;\'1 -r;~:' 00: . ~ . ' .~ - (~ 'y0 \t ~~J ........" o'-- rfJ jjI'( I /JJ ~ 1.11 ~: (OJ, .(.J.J :A -, '0 (01. ~ ft ~ .I F'7. ~ l (f J ~jJ.; , ,c rl (2) t5 ..... / V R12 TB17 TB13 ~o t01 OJ TfOUI.." I \IT r--- Fig. -I.\III ~1f\~ \' I~ ,n.. 0 II ~oilMJol -1IO1no1 "'7' T B 12 R26 ~ 11 B15 JX V1 R36 R34 ....
,.' Fig. 10. Cut all Ii' (J) and R37, to 5/8" . 3KQ (orange, orange, red, silver) resis- OOK or 10, OOOmmf) disc capaciConnect C47 from XV3-3 (S2) to TB21- 1 (C). 6. (/) Fig. 10. Cut all leads on two. 01 mfd ('\l 2 (C). Fig. 10. Connect a4'! piece of orange wire fromC37-C (C) to TB15- 2(C). Fig. 10. Connect a 4" pieceo(orange wire from TB17 (C) to C37-C (C). (C). 15. qn 14. ( I) Fig. 10. Connect the shield from the single conductor shielded cable lead from SlD-7 to TB12- 1 (C).
tI.) tI.) Fig.
1' Fig. 11. Cut all leads on two 2. this end U) (v) silver) resis 1B12-2 (C),, Con- green , 6 volt electrolytic capacitors Connect R14, (with the shorter leads) fromXV2- 3(S2) to TB13- 1 (C). Connect R13 (with the longer leads) from XVI- 3 (S2) to ground lug " G" (C). Fig. 11. Cut both leads on one 4. 7KQ (yellow, violet, red, silver) re9. 3/4" sistor, R14 to 1/2" and both leadsol1asecond4. ;7KQ r~sistor, R13, to lug " G" (C).
#8 Pk. O~O ffi'o .~...~o ...~g~. ::. #8- 32 Tinnerman Nut Tinnerman Angle Bracket 000 O~~~\~~: Screw ,::. Chassis Bezel Side Bracket Control Plate #8- 32x3/8 Brown Screw Brown Screw Fig. 12 #6 Pk.
When ready for use. brown colored is adequate tightening the screws finally, be sure there or with two #8- 32 x 3/8 brown colored screws, two #8- all controls to the furthest counter-clockwise position. on the shafts with the indicating dots pointing as you. shorter plate. The method is to work the rounded portion of each foot into the interior 8. ( ) Fig. 12. Install the rubber feet in the openings provided in the botiom tom plate fits over the outside of the rear chassis apron.
ments that are not completed or instruments that are modified will not be ac- strument to our factory where it will be placed in operating condition for $12. plus the cost of parts replaced due to their being damaged in the course of construction. This service policy applies only to completed instruments constructed in accordance with the instructions as stated in the manual. Instru- possible indications that might be helpful.
#18045 E. 1209 Pin 7 should read 1500 Inco, Long Island City 1, instead of 330KC Electronic Instrument Co., Page 13. va, New York Part supplied may be dual 500KC instead of 750KC. This is a direct replacement. It does not impair the performance of the amplifier in any way. Schematic R22 and R23. Page 16, Symbol #R22, 23 Stock Page 7C, Step 7.
