McIntosh MR71 Tuner Service Information.pdf

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1、MR 71 SERVICE INFORMATION STARTING WITH SERIAL NO. 20B01 McIntosh laboratory inc. 2 chambers street Binghamton, new york MR 71 HJtlnlotb rm m;.w HMnlosh im tumoi fit mttHJMOKK !8Nl simo ItMntosh TRIMMER) MIXER COIL 19 KC PHASE COIL 19 KC TRANSFORMER MPX. LIGHT ADJUST 38 KC OSCILLATOR ANTENNA COIL EL

2、ECTRICAL SPECIFICATIONS Usable Sensitivity 2.5 microvolts at 100$ modulation for less than yfc total noise and harmonic distortion. Audio Frequency Response Within l/2db from 20 to 20,000 cycles. Distortion Less than 0.5$ at 100$ modulation. Capture Ratio 1.5db at 100$ modulation. Muting At least 60

3、db noise reduction between stations. Image Rejection Better than 80db at 90MHz. Hum Better than 70db below 100$ modulation. Output Approximately 2.5 volts; low impedance. Multiplex Channel Separation Better than 35db at 1000 cycles. Multiplex Filter Greater than L|_8db suppression of 19kHz pilot and

4、 38kHz carrier. SCA Filter 50db down at 67kHz to 7MtHz Power Consumption 70 watts, 105 to 125 volts, 50 to 60 cycles. DIAL STRINGING X -N 0 -P i1 g ft p i1 0 o c -P O 11 G 0 G Ph cd i1 0 -P p cd i1 C H G cd O G X .H Q O CJ4 G H 0 0 CT* LU G i1 H 0 rv* a1 cd Ph X 0 -P O Cd Ph . 0 Ph O = -P Ph rs CQ H

5、 o c 0 O Ph O O CM 0 CQ 0 O LU (1 i1 X A cd i1 ! 1A rH X s rl 1 X Ph Ph X G ttj cd cd 0 Ph f- a Ph X n cd 0 0 o X ft P G o Ph 0 G P O rH O Ph i1 O 0 u -P CM -P O rl i| o cd cd -P 0 P G m Ph cd w G 0 LU 0 -P 0 G o ft g c G 0 P 0 0 0 G 0 0 J c!j ciJ 0 ft H rH on 0 O O cd LU rH Ph X O H cd G 0 tl 0 O 4

6、3 1 G 0 ii |t1 O H G bO cd ft i1 G rl 0 H i1 O ra CO J s -P ft rH CQ %_ p i1 O Ph 0 ft G o ra cd Ph s rH O ft # m # # ii CM cA -d- LA X 0 o 0 i1 G G X) G M O cd rH O P *rl G ft *H Js 0 P H 0 P X G 0 cd 0 P ft cd 0 O G 0 0 0 S G P P H *H X rH X ft cd ft ft ft G *rl G H 0 05 11 0 o 0 O x o X P X X O G

7、 o p cd p ft ! G bO cd X 0 cd 0 0 H X bO G rH G 0 G X H G cd cd X 0 H 0 P bDP O 0 Jp H ta a P P CM G TO Is O H O O G srH G H G 0 G a a OO Ph X 0 0 0 ft G X g i _ O G o X ft O O rH fA P ft cd 0 G o G CM o O rH 0 ft cd Opt cd G ft P rH X G 1 ft * G O P rH 0 0 z. 0 rH cd O 0 cd Cd O rH P rH X 0 ft G rH

8、 H 0 0 -rH o 0 P 0 0 G 0 0 G 0 G 1 P 0 cd G H rH 0 0 X G X CO CA X G G GG rH cd O LU P 0 P O 0 P P H GO cd G ft O G o H 0 O 0 X! ft ft Cd *rl cd P O G X Is rG 0 X bO 0 p P H P G G , H O f 0 G G 0 O o O rH P rH 0 0 o G M P G G rH ft cd G O rS, ft rH 0 0 0 G P 0 o G 0 j! e p ft * 0 uj*H 0 G G 0 G 0 p

9、p ft 0 G ftOD1 Cd rH G 0 rl X O H 0 0 cd P X 0) 0 P G i 0 G cO 0 P 0 G G O1 Op 0 O O ft 0 G O 0 cd 0 O *H 0 P 0 ft P bflH G 0 0 P G GHH * *H P PGP G *rl 0 HXX 0 rH Cd 0 o X X o cd 0 cd 0 O 0 0 X S rH G 0 G P G X X cd 3 H G 0 G O p p X rH Cd 0 P ft 0 0 G O X ft O G X X ft ft O d cd -P O rH *h 0 rl OH

10、 CC -H -P d iA p cd cd h rH 0 |3 M4l Ph P P O Td H *h p o! 1 o n 0 |5 cti 4h rt 4*J *H p Ph p TO Ph 00 cd ,5 p 0 0 bo g o o *H 0 0 O Ph bQ 0 *H rH rH 0 f-l Td O M 0H ClJ 0 *H H T) h *h |3 cd Td H bQ Ph *rl rH Ph *H 0 H Ph 0 =tfc 0 g 4 is o g ph g p 0 Ph Ph 0 O-HPEh op 4l o cd Ph t* cd cd cd cd o p 0

11、 43 P bOP Td o (xj P Ph P Ph 0 0 H 0 rH N 0 rH tH g P cd W -H r o Ph 44 Td Is o cd bQlA bD O cd *rl b- g i1 0 0 rH 0 rH Ph 0 S LA cd cd P 4) cd bO 0 *rl Cd g p O bO O HHO *H H P cd H Ph Pi P g C 0 O cd ftp cd 11 0 cd Ph 43 =tt= p cd vO OP p EH cd Ph Cd Ph 0 Ph g rH -P 0 O h O Ph P P bO Ph p p rH cd

12、cd P td-H 0 ,r-3 E P rH IS) Td *H Ph cd p cd OP Ph bfl rH Cd Ph Ph 0 cd *rlH O 0 P 0 P p P 0 *H cd Td 0 O o p o p cd H rf g -9.0 0 g Ph o p 41 Td Ph Ph H -P J Td o P 0 Ph rH -H -H Ph *H P O p ri K O oP O 5 H 0 0 (in Td P _ O 0 p P p *H bO 4h P H bO rH EP Cd rH g p Cd o H CdP o O H cd P X, bO rH r-3

13、K bO i 1 Td cd o Td cd O r5 r*i Ph Ph cd N cd Ph Td 0 Ph Td O Ph Ctf Ph P o o g o o cd Ph GO *rl o O O rH Ph P 0 rH g CO Ph CH P Ph CO Ph fH P o o O O O *H Through ex ternal . OlfjF capacitor to pin 7 of 12AT7 mixer o Same CO o- o 11 Same 1 rH Ph Cd O 0 0 P O bO p -H *H 0 0 0 g O O 0 Ph cd Ph H O CO

14、 SCHEMATIC NOTES 1. R10l| does not appear in unite below aerial number 78B30. 2. R29 had a different value in earlier units. 3. C6 was lOpP in earlier units. 4. R27 was either 1.2K ohms or 2.2K ohms in earlier units. 3. R103 does not appear in units below serial number 67BOO. 6. L6 was not used in s

15、ome units below serial number 21B30; LI was link coupled to L2. 7. G100 was used in some units below serial number 66B33- 8. R38 was 220K ohms in earlier units. 9. C101 does not appear in some earlier units. 10. In all units below serial number 62B00, C7 was 220pF and CI4.3 was .OlpF (disc); R102 wa

16、s not used. 11. In all units below serial number 38B00, R92 and 93 was 680 ohms, Rl|3 was 6.8K, and R6I4. was 220K. 12. R96 was 10 ohms in all units below serial number 39BOO. 13. C58 was a .OlpF (2 section) capacitor in earlier units. llj. R99 does not appear in earlier units. l3. C99 and R100 do n

17、ot appear in units below serial number 43B00. Refer to McIntosh Service Bulletin #114 (part number 038-141) 16. C33 was lOpF in all units below serial number 43B00. 17. R3 was 3K ohms in some earlier units. 18. In all units below serial number 86B6O, C71 is .0027 5% 100V. (Part No. 063-004) 130V K R

18、EPLACEMENT PARTS All parts not listed are common items obtain able from radio parts jobbers. Replacement parts may be obtained when ordered by PART NUMBER from: McIntosh Laboratory, Inc. Customer Service Department 2 Chambers Street Binghamton, New York 13903 (telephone 607-723-3512) CAPACIT0RS Symb

19、ol Number Description Part Number C35 Elect. 10 pF 25V NP 066-005 C43 Mylar . 1 pF 250V 064-037 C59 Elect. 40 pF 200V 066-049 C60 Elect. 50/50/50/50 pF 200/200/200/200V 066-036 C71 Mylar 3300pF 125 V 064-074 C75 Mylar . 1 pF 250V 064-037 C?8 Mica 4700pF 100V 063-005 C79 Mica 4700pF 100V 063-005 C84

20、Elect. 500 pF 12V 066-024 093,94 Elect. lpF 150V 066-050 095,96 Elect. 10 pF 3V 066-110 DIODES D1 Se. rectifier 070-005 D2 Se. rectifier 070-005 D3 Variable cap. diode 070-020 D4 Si. signal diode 070-022 d5 Si. signal diode 070-022 D6 Si. signal diode 070-022 D7 Si. signal diode 070-022 D0 Si. signa

21、l diode 070-022 D9 Si. signal diode 070-022 DIO Ge. signal diode 070-003 Dll Ge signal diode 070-003 D12 Ge. signal diode 070-003 D13 Ge signal diode 070-003 D14 Si. rectifier 070-030 D15 Zener diode 5.6V 070-035 FUSES FI Fuse 1 Amp Slo-Blo 089-001 CHOKES L2 RF coil 122-057 L3 Mixer coil 122-058 L4

22、Oscillator coil 122-007 L5 Filter coil (19kHz phase) 122-008 L6 Choke 1.5 pH 122-032 L7 Choke .47 pH 122-010 l8 Choke 2.5 pH 122-033 L9 Choke 1.2 pH 122-011 L10 Parasitic choke 122-028 Lll Choke 1.2 pH 122-011 L12 Choke 75 pH 122-013 L13 Choke 1.5 pH 122-032 L14 Choke 2.5mH 122-031 L15 Choke 75 pH 1

23、22-013 L16 Choke 1.2 pH 122-011 L17 Choke 2.2 pH 122-001 Ll8 Choke 2.2 pH 122-001 L19 Choke 1.2 pH 122-016 L20 Choke 1.2 pH 122-011 L21 Choke 1.2 pH 122-011 L22 Choke .47 pH 122-010 METERS Signal strength meter 124-005 Tuning meter 124-006 TRANSISTORS (41 Si, NPN transistor 132-042 P 0TENTI0METERS R

24、1 AFC control 134-068 R2 Muting adjust 134-063 R3 MPX light adjust 134-062 R4 Volume control 134-067 R5 Output adjust 134-001 RESISTORS R52 Wirewound 220 ohms 5w 139-009 R53 Wirewound 220 ohms 5W 139-009 R56 Wirewound 2 ohms 5w 139-005 SWITCHES 51 52 53 Ll Antenna coil 122-026 Muting switch Mode swi

25、tch Lamp intensity switch 14-6-022 146-063 148-003 1 122-057 122-058 r coil 122-007 LI (19kHz phase) 122-008 1.5 mH 122-032 47 pH 122-010 2.5mH 122-033 1.2pH 122-011 choke 122-028 1.2pH 122-011 75 mH 122-013 i.5mH 122-032 2.5mH 122-031 75mH 122-013 1.2pH 122-011 2.2(jH 122-001 2.2pH 122-001 1.2(jH 1

26、22-016 1.2pH 122-011 1.2 in 122-011 47pH 122-010 ffiTERS length meter 124-005 124-006 ULSISTORS ansistor 132-042 ITIOMETERS )1 134-068 iust 134-063 adjust 134-062 itrol 134-067 iust 134-001 5SJ.STORS 220 ohms 5W 139-009 220 ohms 5W 139-009 2 ohms 5W 139-005 rfITCHES jLtch 146-022 Eh 146-063 isity sw

27、itch 148-003 T1 TRANSFORMERS First IF 162-040 T2 Second IF 162-037 T3 Third IF 162-037 T4 Fourth IF 162-037 T5 Fifth IF 162-041 T6 Discriminator IF 162-041 T7 Amplifier (19kHz) 162-009 T8 Oscillator (38kHz) 162-010 T9 Baiun 043-226 T10 Power 043-344 VI TUBES 6DS4 (nuvistor) 165-013 V2 12AT7 165-017

28、V3 6BN4A 165-008 V4 6AU6A 165-004 v5 6AU6A 165-004 V6 6AU6A 165-004 V7 6AU6A 165-004 V8 6CS6 165-011 V9 6HU6/EM87 165-025 V10 6BN8 165-009 Vll,12 6BL8 165-007 V14 6EA8 165-044 vi5 12AU7 165-018 FRONT PANEL AND TRIM Volume knob 043-253 Mode knob 043-253 Muting knob 043-253 AFC knob 043-253 Tuning kno

29、b 043-272 Front panel (complete) 043-356 Front panel glass 016-014 End cap (right) 018-043 End cap (left) 018-044 V13 LAMPS Neon lamp 058-001 #1847 (meters & stereo) 058-008 Festoon (dial glass) 058-032 MOUNTING SYSTEM Shelf bracket (right) 043-592 Shelf bracket (le: Mounting template Hardware packa

30、ge MISCELLANEOUS ! LDR network SCA filter PM dipole antenna Dial glass Pointer Coax connector (7) Line cord Dial cord Fuseholder Shipping carton Owners manual Plastic feet Tube shield (7 pit Tube shield (9 pit SCHEMATIC PART NO. 03 Shelf bracket (left) 043-593 Mounting template #100 038-179 Hardware

31、 package 04.3-4.50 MISCELLANEOUS ITEMS LDR network 144.-010 SCA filter 180-004 FM dipole antenna 170-033 Dial glass 016-073 Pointer 043-814 Coax connector (75 ohm) 127-015 Line cord 170-021 Dial cord 043-815 Fuseholder 178-001 Shipping carton 043-947 Owners manual 038-029 Plastic feet 017-041 Tube s

32、hield (7 pin) 073-005 Tube shield (9 pin) 073-006 10C0226S6-M8331 SCHEMATIC PART NO. 038-331 MODEL NUMBER: MR 71 MODIFICATION: This modification increases stereo separation on MR 71 tuners to better than 35 db separation. This modification is in units with serial numbers above 45B00. DESCRIPTION: Th

33、e stereo multiplex detector in the MR 71 tuner is a self matrixing detector. It automatically recombines the L+R and LR stereo information to produce L and R output. The SCA filter causes a slight loss in the LR portion of the composite multiplex signal. This limits stereo separation to about 30 db.

34、 Sepa ration is improved by increasing the difference signal gain in the tuner left and right audio amplifiers while leaving the common signal gain unchanged. This is done by connecting a RC network between the cathodes of the R and L in put audio amplifier stages. PROCEDURE: 1. Connect a 27K 5% Vj

35、watt resistor and a .0015 MF 10% capacitor in parallel. Connect this network between pin #8 on one 6BL8 audio tube to pin #8 on the other 6BL8 audio tube. 2. Feed a multiplex signal modulated with 1KC audio left or right channel only into the tuner antenna input. Tune the tuner to the MPX signal. Al

36、ign the 19KC phase adjust (coil L5) for maximum stereo separation. It is pos sible to obtain greater than 35 db separation between channels. NOTE: Before making this alignment be sure the MPX generator is accurately set up. View the composite stereo signal at the generator with an oscilloscope. Do not attempt to estimate stereo separation by viewing the tuner discriminator output at TP 2. The signal at TP 2 should NOT look like an ideal multiplex signal. MATERIAL NEEDED:!, ea. resistor, 27K 5% Yzw 1. ea. capacitor, .0015 MFD 10%