McIntosh MR74 Tuner Service Information.pdf

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1、! RVIC E ll FC Rl U T 1 Dft STARTING WITH SERIAL NO. A Cl 001 f MclNTOSH LABORATORY INC. 2 CHAMBERS STREET BINGHAMTON, NEW YORK MR 74 MR 74 ELECTRICAL SPECIFICATIONS AM TUNER SECTION SENS IT IV ITY SELECTIVITY, ADJACENT CHANNEL 75nV IHF (external ant.) 35 dB minimum IHF in NORMAL Position. 45 dB min

2、imum IHF in NARROW Position. SIGNAL TO NOISE RAT 10 45 dB IHF minimum; 55 dB at 100% modulation. IMAGE REJECT ION 65 dB minimum 540 kHz - 1600 kHz. HARMONIC DISTORTION Does not exceed 1% at 30% modulation. FREQUENCY RESPONSE 3.5 kHz - 6 dB, NORMAL Position. 2.1 kHz - 6 dB, NARROW Position. FM TUNER

3、SECTION USEABLE SENSITIVITY 2.5 microvolts at 100% modulation (+75 kHz deviation) for 3% total noise and harmonic distortion IHF. SIGNAL TO NOISE RAT 10 70 dB below 100% modulation. CAPTURE RAT 10 1.5 dB mini mum. HARMONIC DISTORTION Mono: Does not exceed 0.3% at 100% modulation +75 kHz deviation. S

4、tereo: Does not exceed 0.7%. AUDIO FREQUENCY RESPONSE +1 dB 20 Hz to 15,000 Hz with standard de-emphasis (75 psec.) and 19,000 Hz pilot filter. SELECT IVITY ADJACENT CHANNEL: 6 dB minimum IHF in NORMAL Position 15 dB minimum IHF in NARROW Position ALTERNATE CHANNEL; 58 dB minimum IHF in NORMAL Posit

5、ion 88 dB minimum IHF in NARROW Position SPURI0US REJECTION 90 dB IHF mini mum. IMAGE REJECTION 95 dB minimum, 88 MHz - 108 MHz. STEREO SEPARATION 35 dB at 1,000 Hz. SCA FILTER 50 dB rejection from 67 kHz to 74 kHz. 275 dB per octave slope. SIGNAL 1RENGTH 1 L 19 kHz 19 kHz 38 kHz 19 kHz AMP PHASE LI

6、NEAR SCA FILTER MUTING FM SELF MATRIX DETECTOR RIGHT GATE AMPO LEVEL ADJ. DE-EMPHASIS MODE SWITCH STEREO FILTERS VOLUME CONTROL Ol -OR Ol Or VARIABLE OUTPUTS FIXED OUTPUTS jcK DIAGRAM MR 74 SCHEMATIC NOTES Unless otherwise specified: Resistance values are in ohms, i/k watt, and 10% tolerance; capaci

7、tance values smaller than 1 are in microfarads (pF); capacitance values greater than 1 are in picofarads (pF); inductors are in microhenries (pH). Printed circuit board components are outlined on the schematics by dotted lines. The circled numbers around the dotted 1ines correspond to the numbers on

8、 the PC Board layouts. The heavy lines on the schematics denote the primary signal path. The terminal numbering of rotary switches is for reference only. All voltages indicated on the schematics are measured under the following conditions: a. Use of an 11 megohm input impedance VTVM. b. All voltages

9、 +10% with respect to chassis ground. c. No signal at input or antenna terminals. d. AC input at 120 volts, 50/60 Hz. e. Front panel controls at: Tuning indicator 100 MHz (no signal) Vo 1ume Fu11y CCW Mode AM (to measure AM section) FM (to measure FM section) Muting Out Stereo filter Out Panel Light

10、s Bright Selectivity Normal f. Voltages shown in rectangles are measured with selectivity switch in the Narrow position. TUNING CONDENSER DRUM (TOP VIEW) FM SECTION AM SECTION MR 74 154 - 523 MPX SECTION / | MODE SELECTOR | Ir.n0WER - 40V DC PIN 9 AM PC BOARD S202 DIAL SCALE SENSITIVITY INSULATED PO

11、INTER WIRE POINTER V20I LIGHT (MPX SECT 40V DC I 2.2 K 1/2 W | 0206 Y l 24V cr #1866 #1866 #1866 #1866 #1847 #1847 S204-2 REAR I MODE SELECTOR I VOLTAGE REGULATOR C 217 If R230 H .001. IM i rvg5 21 6V IA M OV |ov JL GRN/WHT (19)- PIN 6 AM PC BOARD V-/ OV JL GRN/WHT AMPLIFIER SECTION MULTIPATH AMP PO

12、WER SUPPLY SECTION PC BOARD 044-298 MR74 154-521 TO POWER SUPPLY SECTION AMPLIFIER SECTION 154-519 L402 T40I MR 74 MR 74 mmswmMMi!* _ _ AM PC BOARD MR 74 00 o m 10 o ro o CM o CM ro CM ro M O in 1- o r _l (T 00 cn _i 1- o o cn o oo o 0. o LLJ on O LLJ on LLJ 2 o_ O LLJ x 4_* p. c m G X CD CD X) c 0

13、* X c 13 !_ 03 1- =3 C Z3 3- X 03 O o on CT CD c X D on CD j- 0 Z) , 1 o c CD 1- 4-J 4-J CQ CO LT O x 0 4-J CD LT CO ID CO CJ in - CQ . (1) on Ll L O 2 c 4 x - CJ CM 0) CD c d i_ CD r X U Cl) CD X on - - p p X - . X i_ G g CD CM -G !_ CD i_ i_ P i_ CD 03 - CD CD 03 X 03 CD X 03 X Cl) 0) 03 L. P CD Q

14、_ 03 T 21 DC CD G i_ 1 C CL _ _ C 3_ Q_ X CD CD ZJ X CD L. CD in CD c 2 o o CD 1 o on X X - 4-J CL CD 0 5 03 03 *- CD CD 21 X (D 4-J N i_ 3- O O i- O CD CD X l_ X 0) 0) C CD in c LT C_D CJ CD 21 X - CD Q. CD - - Ll D C_D 0 O . +i cn N C c r ,- X G X J_ 0 X CT CD 0 - X 0 2 cz CD 2_ . C Z3 2. c C . .

15、0 ex OO on x X JZ r-. x r. E CD r-. u u O CD U i_ 21 CD 1 Z! CD O X o l/l 03 L_ o 21 1 03 I o X 0 1 CM m -X LT X r-. oo ex uo ,+7 r - 4-J X 3 QC CD G O i- CD 2; i- X 4-J CD X X Cl G X C 4-J c E L- CD 13 G G C CD X 4-1 C CD x _Q x m 0 c CJ 4-1 G 4-J (D ex G I CM .- X C - X . exx 4* C c G X LT C I) 0!

16、 03 X m CV- CL CZ 4-J 0 1 in X CD - - 4-J 4-J rr 13 i_ E u C Cl CM - L_ 3- G c r. - CD 03 0 G 3- u i L_ _C (D X X ZJ x 2: r- O L- C C (J . o 4-J 3- U G - X U 4-J C X G C x 03 CD J CD X C G M- (D 4-J O G m G c P CD CD x -X r- c CD . . 4-J X X X X CO X X CL - CZ 1 X Q_ 4-1 - 03 E 1- c G G G 2: z i- O

17、G x E x . i o u in C G G 21 03 in in x era X Ll in CD CD G G 1 * X i- X U x p- G 21 u (D CD G G Q UG CT * (D 4-J 2 m 3_ G 3 cr J 4-J - 0 G p L on X 03 - x on G X m E CD 4- G X X c O - X 4-J 4-J . i_ L. l_ 03 4-J 1_ 4-J -X c u G 0 0 c C in r. G G G E - J X 4-J 4J . i O X: Z CD U u L_ QC G G x 2 c C 2

18、1 CD IX 03 21 X m G LXI ex X C X 4-J G X 2 S . U G ZJ G O o O 1 . CD U r O X c - . z 03 x . in u C o - 1- 1 L- in G X X 1 - P G o 4-J X E - 4-J o m X 2 x c G G t ZJ c c C x X 1 CD X o- G G 1- 4-J G U cn X CD E O u i O c E c L- CLX c G G X - c 03 CD - CD X p X c CQ U D Q_ c E G X c G ZJ o CkC ex CL O

19、 l U G C73 in CT - G CD in X Z3 G G c E x G L. s_ . 4-1 X in x cn X 0 O G G G 03 c G m g X 0 X C in j_ ZJ . in c E X in c o CD X u 4-J G 0 G in C 0) 4-J G X G G G in CJ X 4-* 03 4-J i_ i_ G G x X X C 03 U X in X G X C c G x X in (j X CM G U 4-J 14 G U G G X E 21 m 1- z G x G X X G c CD U G U U X X *

20、 cn c CD 4-J L- i_ G G i_ u Cl X . X X X X O c . in U u X X O Ll TUNER SIGNAL GENERATOR INDICATOR DIAL - ADJUST TEST LIMITS REMARKS SETTING FREQ. COUPLING MODULATION TYPE CONNECTED TO 1 1 c i j- E co O -LA L 21 i- O 4-1 -*-* 1 X L. CD CD O CD CC C 1 i- C l/T * CO QJ (U i- c E CM CD CD CD LT . 0 C L.

21、 L. O 4- 4- CQ i_ CM *- J-l O LT CD CD 0) LA x c L (U LA X C L. LT2I O -M *. 1 0) CD 4-J O (D CD 4-J CC 1 Iter attenuation at 10kHz modulating frequency gnal to noise ratio may be measured. MR 74 D1 0 7,1 0 8 S i. diode 070-022 D201,202 s i. diode 070-031 D203.204 Si . diode 070-031 D205 Zener diode

22、 24V 070-049 0401 S i . diode 070-003 D402.403 Si . diode 070-022 D404 S i . d i ode 070-022 D405.406 Ge. signal diode 070-003 D407,408 Ge. signal diode 070-003 D409 Ge. signal diode 070-003 D501 Si . diode 070-022 D502,503 Ge. signal diode 070-003 CHOKES & COILS LI 1 St RF coil 122-115 L2 2 nd RF c

23、oi 1 122-114 L3 Mixer coi1 122-113 L4 Osci11ator coi1 122-112 L101,102 Choke 75pH 122-013 L40I Choke 1MH 122-092 L402 Filter coil (19kHz) 122-094 L403.404 Fi 1 ter coil (SCA) 122-093 L 501 AM antenna 122-110 L502 AM RF coil 122-086 L503 AM oscillator coil 122-085 L504 Choke 1 . 2|_iH 1 22-011 TRANSI

24、ST0RS Q1 ,2 S i . M.O.S. F.E.T. 1 32-088 Q3 S i . NPN transistor 132-01 5 Q4 S i . J unction F.E.T. 1 32-084 Q5 S i . Junction F.E.T. 1 32-068 Q6 Si . M.O.S. F.E.T. 132-086 Q201,202 S i . NPN transistor 132-056 Q203,204 S i . NPN transistor 132-090 Q205 S i . NPN transistor 132-054 Q206 S i . NPN tr

25、ansistor 132-065 Q401 Si . NPN transistor 132-092 Q402 S i . NPN transistor 1 32-090 Q403,404 Si NPN transistor 132-092 Q405 Si . NPN t ransistor 132-092 Q406 S i NPN t ransis tor 132-042 Q501,502 Si NPN transistor 132-082 Q503 S i NPN transistor 132-082 Q504 Si NPN t ransistor 132-090 REPLACEMENT P

26、ARTS All parts able f.r om not listed are common items radio parts jobbers. obtain- Replacement parts may be obtained when by PART NUMBER from: ordered McIntosh Laboratory, Inc. Customer Service Department 2 Chambers Street Binghamton, New York 13903 (telephone 607-723-3512) CAPAC1 TORS Symbol Numbe

27、r Desc ription Part Number Cl 09 Ta. Elect. 2 2pF 20V 066-148 C20I,202 Polystyrene 2700pF 064-093 C20 3 Polystyrene 4700pF 064-091 C204,205 Mylar .1pF 064-067 C207 Elect. 1OpF 63V 066-178 C212,213 Elect. 2 2 pF 35 V 066-179 C215,216 Elect. 1OpF 63 V 066-178 C2 1 8 Mylar ,22pF 250V 064-068 C2 19 Elec

28、t. 5/300/150/1OOpF 200/50/50/30V 066-180 C220 Elect. 1 OpF 63V 066-178 C401 Mylar .22pF 250V 064-068 C405 Elect. 1 OOpF 25V 066-161 C4o8 Elect. 1OOpF 25V 066-161 C41 0 Polystyrene 27O0pF 63 V 064-093 C41 1 Ta. Elect. 1pF 35V 066-147 C41 3 My 1 a r . 1 pF 250 V 064-067 C41 5 Mylar .22 pF 250V 064-068

29、 C416.417 Polystyrene 4700pF 064-091 C502 Polystyrene 4700pF 064-091 C503 Ta . Elect. .47 pF 35 V 066-167 C 50 7 Ta. Elect. 3.3pF 35V 066-170 C51 5 Polyester .01 pF 064-101 C51 8 Polystyrene 2700pF 63 V 064-093 C520 Elect. 1 OpF 63V 066-178 C527 Elect. lOOpF 2 5 V 066-161 DIODES D1 Ge. signal diode

30、070-003 D2,3 Si. diode 070-022 D101,102 Si. diode 070-022 D103,104 Ge. signal diode 070-003 D105, 06 Ge. signal diode 070-003 diode 070-022 diode 070-031 diode 070-031 er diode 24V 070-049 diode 070-003 d i ode 070-022 d i ode 070-022 signal diode 070-003 signal diode 070-003 signal diode 070-003 d

31、i ode 070-022 signal diode 070-003 HOKES & COILS RF coil 122-115 RF coil 122-114 er coi I 122-113 i 1 lator coi1 122-112 ke 75 pH 122-013 ke 1MH 1 22-092 ter coi 1 (19kHz) 122-094 ter coil (SCA) 122-093 antenna 122-110 RF coi 1 122-086 osci11 a tor coil 122-085 ke 1 .2 pH 122-011 TRANSISTORS M.O.S.

32、F.E.T. 132-088 NPN t ransistor 132-015 Junct ion F.E.T. 132-084 Junct ion F.E.T. 1 32-068 M.O.S. F.E.T. 132-086 NPN transistor 132-056 NPN transistor 132-090 NPN transistor 132-054 NPN transistor 132-065 NPN transistor 132-092 NPN transistor 132-090 NPN transistor 132-092 NPN transistor 132-092 NPN

33、transistor 132-042 NPN transistor 1 32-082 NPN transistor 132-082 NPN transistor 132-090 F201 FUSES Fuse .5A s1o-blo 089-020 R228 POTENTIOMETERS Vo 1ume control 134-217 R236 RES IST0RS Wirewound 1.8n 1W 139-077 R237 Wirewound 2n 2W 139-005 S203 SWITCHES Stereo filter switch 146-137 S204 Mode selecto

34、r switch 146-135 S401 Muting switch 146-138 S502 Selectivity switch 146-154 T 1 TRANSFORMERS Ba 1 un 043-226 T2 FM IF transformer 162-059 T3 FM 1 F t rans former 162-042 T 1 01 FM IF filter input 162-053 T102 FM IF filter output 162-052 T1 03 FM IF filter input 162-053 T1 04 FM IF filter output 162-

35、052 T1 05 FM discriminator 162-036 T201 Power transformer 043-865 T 401 FM RF transformer (19kHz) 162-055 T 402 FM RF transformer (38kHz) 162-054 T 501,502 AM 1F t rans former 162-050 T503 Matching transformer 162-061 MODULES LDR network 144-013 M401 METERS Signal strength meter 124-005 M501 Tuning

36、meter 124-006 1C101,102 INTEGRATED CIRCUIT Integrated circuit 133-002 FN1 FILTERS FM fi 1 ter 180-009 XF501 AM filter 180-010 LAMPS #1847 (Meter) 058-008 #1866 (Front Panel) 058-014 #1828 (MPX) Festoon lamp FRONT PANEL Front.panel Front panel enc Volume knob Tuning knob Mode selector 1 Stereo fi1 te

37、r I Selectivity knc FM muting knob MOUNTING Shelf bracket Shelf bracket Mounting tempi. Hardware packai MISCELLANEI Plastic feet Tuning shaft Shipping carto Push termina1 Owners manual Dial cord Dial pointer Shorting plug AC line cord FM dipole ante Fuseholder Dial glass 15C0214S7 MR 74 MR 74 #1828

38、(MPX) 058-027 Festoon lamp 058-032 FRONT PANEL & TRIM Front.panel 044-303 Front panel end caps 018-120 Vo 1ume knob 044-372 Tuning knob 043-272 Mode selector knob 044-372 Stereo filter knob 043-428 Selectivity knob 043-428 FM muting knob 043-428 MOUNTING SYSTEM Shelf bracket (right) 043-622 Shelf br

39、acket (left) 043-623 Mounting template #100 038-179 Hardware package 043-446 MISCELLANEOUS ITEMS Plastic feet 017-041 Tuning shaft 021-067 Shipping ca rton Push terminal (antenna) 074-032 Owners manual 038-552 Dial cord 044-226 Dial pointer 043-876 Shorting plug 1 27-021 AC line cord 1 70-02 1 FM dipole antenna 170-033 Fuseholder 178-001 Dial glass 15C0214S7-M2551 MR 74 SCHEMATIC PART NO. 038-551