Scott-348B-Service-Manual 电路图维修手册.pdf

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1、SPECIFICATIONS TUNER (FM-MPX) Scott . where innovation is a tradition SCOTT SERVICE MANUAL FOR MODEL 348-B Usable Sensitivity (IHF) -3% THD, Noise and Hum Signal to Noise Ratio Total Harmonic Distortion, Mono Frequency Deviation (Drift) less than *Frequency Response Capture Ratio Selectivity (400 kH

2、z off channel) Spurious Response Rejection (Cross modulation rejection) 19 kHz Pilot Suppression 38 kHz Sub-carrier Suppression AM Suppression Tuning Range Accuracy of Calibration Separation l.5uv 65dB 0.8% .02% 50 to l.9dB 45dB 90dB 40dB 60dB 55dB 15,000 Hz+ 1 dB - 87 to 109 me 0.5% 40dB *This is l

3、imit of FCC Stereo Broadcast specifications. All H. H. Scott tuners have far wider frequency reponse. AMPLIFIRR TaJ)e Ou,tput Rated voltage to tape recorder Recommended load resistance: greater than Recommended cable capacitance -less than tfag. Low . - _In,put Impedan.E,e Signal for rated output (s

4、witch selected S/N Ratio !ape Head ,-Input. ,Im2edance Signal for rated output S/N Ratio Hgh Level Inputs -Input m2eance Signal for rated output S/N Ratio Frequency response in flat position Treble Controls: Boost and Cut at 10,000 Hz. Bass Controls: Boost and Cut at 50 Hz. Lousness Compensation, ma

5、ximum Rumble filter Music Power 4 ohm 8 ohm Rating (watts/channel) 0.8% harmonic distortion Continuous Output -Single Cannel 8 ohms 0.8% Harmonic Distortion Continuous Output -Both Channels 8 ohms 0.8% Harmonic Distortion Total Harmonic Distortion at rated output Frquency Response -Power Amplifier 1

6、w Power Bandwidth at rated distortion (IHFM method) Hum and Noise Damping Factor Line Voltage and Frequency Power Consumption 117 volts, 60 Hz 1 C Copyright H. H. Scott, Inc, 1967 0,5 V 200 k ohms 200 pF 47 k ohms 3,5,9, mv 65dB 47 k ohms 3.0 mv . -52dB 47 k ohms 0,5 V -80dB 17 to 30,000 Hz+ ldB - 9

7、dB -9dB 9dB -9dB +8dB at 50 Hz +3dB at 10,000 Hz 8dB 50 Hz 60/60 watts 50/50 watts 40 watts 30/30 watts 0.8% 20 to 20,000 Hz+ ldB - 20 to 2,000 Hz -80dB 20 105-125 v, 50-60 Hz 35-175 w Form D-348-B-2W RadioFans.CN 收音机爱好者资料库 348-B AUDIO SECTION EQUIPMENT JIBEDED Audio Oscillator VTVM Oscilloscope VO

8、M Load Box Attenuator Distortion Analyzer Variac or 117 Regulated line FM Generator Multiplex Generator Set Controls to the Following: Front Panel Input Selector Stereo Selector Tone Controls (Bass again note signal lost. Remove signal from Tape In Jack and insert in Tape Out Jack. Note signal resto

9、red. 15. Preamp Gain Chesk Return signal input to Extra input and adjust level for output at 1 kHz of 0 dB-on 3V scale with Loudness control at maximum. Turn Loudness control to minimum-Turn input selector to Phono. Attenuate -45 dB and plug input into Phono input. Turn Loudness control to maximum.

10、Output should be 1 1 dB on 3V scale. Switch preamp sensitivity from Max. position to other positions and observe the following gain change with respect to the Max. position: Position Med. Min. Output -5 1 dB .10 1 dB Return preamp sensitivity switch to Max. position. Turn Loudness control to min. Tu

11、rn input selector to MIC. Remove input from phono input and place in MIC input (front panel). Turn Loudness control to Max. Note output of -1 1 dB on 3V scale. Repeat sensitivity check for MIC position. Note same gain changes as in phono position. 16. Phono and Mcrophone Freguency Respons Check Mic

12、Fre_quencx 1 kHz Phono 0 dB Flat Response 10 kHz 100 kHz 17. Hum and Noise Checks Selector Switch Position EXTRA 1 and 2 PHONO (shorted inputs) MIC (shorted inputs) . 14 2 dB _+13 2 dB Loudness Max. 5.0 mV 20.0 mV 10.0 mV 18. Repeat, Step 2 through 1,7 for R_!.ght, Channl. 19. usig Test Bulb 1 w Che

13、ck 4c Qutlets-1 Bla.k is Switched. 5 Loudness Min. 3.0 mV 3.0 mV 3.0 mV Q401,Q402 -QA-10 0 4 5 - . . o: :.o: . : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , I I a . o . . 3 . .-.-:.:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . W: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . + C405 . . . . . . . . . . . . . . . . . . . . . . . . . 0 I O I . . . . . . I O O . . . . . . -. . . . . . . . . . . . . . . . -.

15、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I R407 . . . . . . . . . . . . . . . I o O O O O O 0 . . . O . IO . 0 IO . . . . . . . . . . . . . . . . . . . -. . . . . . . . . . . . . . . . . . . . . :.- . . . . . . . . . . . . . . . . .

16、. . . . . . . . . . . . . . . . . . . . . . . C406 I/ill . . . . . . . . . . . . . . I O I . . . . . -.-. 0 0 . I . . . . . . . . . . . . . . . ,:. . :. . . . . 2 .-.:.:c,: . . . . . . . . . . . o . . . . . . . . . . . . . . . . . . . . . . . I . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., . . . . -. . . . . . . . . . . :.- . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,. . . . . . . . . . . . . . . . . . . . . . . . . . . .

18、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I I . . . . . . . . VI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ac . . . . . . . . ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

19、 . . . IO . . . . . . . . . 10 . . . . . . . . . . . . . . . + . . . . . . . . . . . . . . . . . . . . . . . . : :.C402 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 . .

20、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21、 . . . : . . . ,. -.-. . . . . . . . . . . . . . 0 . . . . . . C401 8 . . . . . . . . . . . . o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -.- . . . . . . . . . N 0 : 6 POWER SUPPLY Z-PC-PS-7 00 7 TO SUPPLY VOLTAGE. ANO COLLECTOR OF SERIES REGULATOR TRANSISTOR TO SASE REGULA

22、TOR OF SERIES TRANSISTOR MITTER Of= SERIES TO REGULATOR REGULA.TE D +30V 8 10 r40.2 R401 R403 2.2.K 1.81. 1 0 1 /2w + I C401 C405 50/75. .001 I I Q402 I QA- 10 I D401 D2-1 2 POWER SUPPLY Z -PC-PS-7 NOTE5: UNLESS OTHERWISE SPECIFIED I. RESlSTANCE IN OHMS 10 CAPAITANCE IN MFDS RESISTORS l/4 WATT TRANS

23、I.STOR 4 + R404 C404 R40G R407 15 K S0/30 3:to 15K 5W C402 R-405 100/15 IOK C40Co 3so 6 l I + I C405 I 10/60 I I I Q4-01 QA-10 I I I 00 REGULATED +l2V f . B+ L.E.t=T !PUT RIG.HT INPUT Ql Q101,Q2,Q102 Q301-2N2924 0 0 . . . . 6 . .: . :; . . a . . . . . . . . . . . . . . . . . . . . :-:.- . . . . . .

24、. . . . . . . , . . . . . . . . . . . . . . . . . . PC-125 2N2925 . - .-:,i:. ft . . . :, . . . :, 4 . . . . . . . . . . . . I o . . PREAMP Z-PC-P-10 r 8 I I I I I I I I I I L R40I 470 Cl + 25/zs c.101 PREAMP C401 50/30 RIOZ IOOK C2 250/3 - Ct02 250/ - RI03 70 + RI04 12.0 K Z-PC-PIO fEE.DBAO( tJETWO

25、R.1 BZO RI05 BZO Rl06 Z20K C.5 25/25 R.8 1.2K RIOO I.ZI + C4 100/ C.104 100/eo CI0!5 25/ZS + RI07 5.-K FEEDBACK NETWORK -.J 7 RIO ZZOK RI 10 ZZOK RIO!: 1.51 RI I RI I 2.?.M 10K ISK !OK A.3 R5 3301. I K RG 14 2.2K SCRATCH Fll.TER, NOISE FILTER I-BlE R7 SALANCE POT 16 IOOK T.C. BYPASS 18 T.C.8YfASS 19

26、 SCllATCH FILTER, 5 RI07 NOISE FILTER IOOK BAlANCI: POT 1:3 Rl4 I . . - . . . . . . . . . . . 2 JJMPER . . . :,.-. . . . . . : . . . . . . . . . . . . .-: . . . . . . . . . . . . . . . . .:. . . . . . . . . . . . . . . . - 2 .3 Rt2 l.iOK CG 10/25 t t:113 Rl5 2.7K GOO Rll3 RI 1 5 27K 660 CIO, 10/2- +

27、 Rll2 RI 14 1 5 0 K 2.7K - JUMPER 8 . . . . . . . . . :-.:.;,:-:-. . . . . . . . . . . . . . . . . . . . TREBLE - 7 R14 I 2.7K I 5 Oz + OUTPVT 2N29:l5 co I 25/25 I C7 + RI 1001;1 4.7K I I I 9 I B+ (20 - 0) I I I Cl07 RI li, I 1 00/(;+ 4.7K I Q102 CI08 I 2N29/l.5 Z5/2 . 7 OUTPUT I I -4i1, L GROUNO_J

28、2 2 NOTES: I. UNLESS OTI-IERWISC: SPECIFl.O: RESISTANCE IN 01-!MS CAPACITORS IN MFDS RESISTORS 1/zWATT 2. ARROWS ON POTS !CATE CIII ROTATION liT If. LtFT CWNNEL SASS CONTROLS ON SAME CONCENTRIC SHAFT (FRlCT10N CUJTCH) 4 RlGHT ,._ LEFT CI-IANNEL TR6LE CONTROLS ON SAM CONCC:NfRIC SHAFT (FRICTION CLUTC

29、H) f i Q1,Q2,Q101,Q102-QA10 Q3, Q103-QA17 0 0 DRIVER Z-PC-D-7 0 I FEEDBACK FROM OUTPUT LEFT-BIAS D40DE STRING LEFT +RIAS DIODE STRING RIGHT 1:llP5 ClLOOE. S rP1NC RIGHT l?IGHT - BLAS DIODE TRIN6 F Dtl-ACI. rR()M OUTPUT LEFT INPUT GROUND GROUND RLGMT INPUT r, I I R8 1 3,3 K I I I I I I I I - Cl 25/:2

30、.S C5 47uu., R7 .;SK R2 .3.SK 270 . - Rl 7K R4 16K CZ 25/25 6AL. C4 33uY. Q1 QA-10 I I cs 12.SOd RI: 2ao I I I I !Tl,. RIG 390 L.-G LEFT LOWE! BASE DUAL DRIVER Q3 OA-17 Rl5 82 C7 DI ,01 SRl-5 10 7 - LEFT CENi.F.R Z-PC-D-7 5 RIO 15K Cb - Al6 47 R9 Z2.0 flAS RI I IK - 8 RI 11 I t. RIZ Rl12 3.3K RI05 R

31、IOt 3.3 K 1:.:K 2:TK 101 cro7 I 39K SRl-5 .01 ._-/JK11i,o I I 1 12 14 10 15 J - -. - RIGHr UPPER RIGHT 6ASF CENTER 9 RlG;H r LOWER BA:.E 0 GROUND NOTES: 1.UNLE:5.S 01HERIAIISI: SPECIFIED: RESISTANCE IN OHMS. CAPACITORS IN MFOS. R(SI.ST01?5 141NATTS ARR01111.S ON POTS INDICATE CW ROTATION HIGHEST S(R

32、.IES NUM6ES R2.0 Rl?.O C7 Ct07 DI UIOf 3 QIOS EMITTER CIRCUIT (Output Stage) . . . I I I 0 EMITTER 5 6 R2 39K 1 /2. W ,. . ,o . 0 . I I -RI .82 SW R3 N 0 . . 0 . - 3 .3 .a. IW . . R4 .82 5W EMITTER Z-PC-E-2 . at Z-PC-E-2 12 RI03 3.3-2. IW RI04 .82 5W 10 0- M . I u A, 0 Rl02 39K Vzw 0 I I 2 I I 1sj 0

33、0 348-B TUNER SECTION QUI.PME!ff, .EDI?. Audio Oscillator VrvM Oscilloscope VOM Load Box Set Controls to the following: ,nd Ditoion d) Using ant and mixer coils at 92 MHz and trimmers at 106 MHz, peak front end for maximum sensitivity. Must obtain 30 dB quieting at 2 uV input at 92 and 106 MHz. Note

34、: Unit must have bottom cover on and front end clip attached to bottom cover for final measurement. - e) Recheck distortion, lk uV input 400 Hz max. distortion 0.6%. FM Hum Check f) Tune to 91.5 MHz, drop from reference. g) Tune to 90 MHz. in output of 12+2 dB - lk uV input (modulation off), measure

35、 minimum of 55 dB Plug may be reversed if necessary. Change modulation from 400 Hz to in output from 400 Hz reference. 11 Note decrease f?7 kHz Tra.P._ Adjus,tll!e!lt h) With 67 kHz generator modulation and low capacity scope probe at terminal 5 on MX-14 board, adjust L-4 (LV.015 PC) for minimum ind

36、ication on scope. Calibration Check i) Check calibration against stations, max. tolerance -+0.2 MHz. - Muting Threshod djst j) With nit tuned to 88 MHz, push muting switch on. Adjust threshold adj. pot (R-1) of Z-PC-NS-4 until hash Just disappears. Audio Hum Chck k) With unit tuned to 88 MHz and mut

37、ing ON, max hum each channel 2.0 mV (Tape output jack). 2. ultiplex Ali;L204 . . vv. L J o 1.JAh R.206 . -1 :R201 czo5 -GB 4 . : 220 . 11.3V -005 C20IS C) r - -1 Q203 r L203 - 1001 _ 0 LZOZ C) C 2. 2.1.1 h. - C204 . 001 L. c2oz. C L20I j : : ; c203 CZOI SPF ( NPO I I I L r,., - f ,300.s?. FM ANTENNA

38、 GND. f I I FM FRONT END Z-FM-IG HIGHEST SERIES NO. R217 czze L207 0201 TZOI Q204- 0 w 000 .33h I I QRF-.3 0 . - .7SV I I 10V R2JG I, 2V II , I C207 r .005 II. . Qc:01 QRF-3 C227 .001 , f R.217 I I /Ill - -_ 1 - - _ _J A A YVv R207 ;RZOB C2l7 C21B 220K : : : 2,2M C .001 .z2/2so /I ,I NOlES I. UNLESS

39、 OTHERWISE SPECIFIED: RESISTANGF. IN OHMS 107o CAPACITANCE IN MFD S , RESISTORS 1 14-WATT. 2. J.NOICATEO SUPPLY VOLTAGES MAY VAFN ABOVE OR BELOW NOMINAL VOLTAGE SHOWN FROM MODEL TO MODEL. 3. 0 C VOLTAGES :15 7,. MEASURED WITH 20KSl/V VOM. 4. ARROWHEADS INDICATE MAIN SIGNAL PATH. fcz20 CZ2I : - 12 Pf

40、 NPO I I , I V R210 IM 0201 DGM?. - . R21i: 220 C2Z4 .oo, fl I ,. L207 0 ,33.,A,i/. CZZ3 r - .001 I AAA II I vv. R211 tc222 I 47 : . I I 1-tOP-f I 000 , METER - - See Page 20 for meter 1 C228 I0.7MC IF- 5NPO OUTPUT . - 11 V . /:. R2l3 C . 4.7K G204 , QF-2 -.# 3.IV 3.GV -, I I II CZ25 I SPF I C I K l

41、 CZ2 : .oos !-rV 10.7 PC3 ,- C303 1,-02 3 _ _J ,. - SQUELCH ,._,.,O MPt AGC - D301 DG.,.2 0302 DGM2 470 C307 T 330 m,.uu.r C308 nd2 C30S G.e pf T302: Tr;tv 10. 7 PC3 s -C30i T-02 nn r- - - - :-, I 4 - 1001. C31o .,. 330 rm M.41.f C30J ,I-02 r- lET AGC - r;t 3()4 2.7f,1 0305 OC.M- - _, ,o 17 - T304-TP.v t0.7 OPC D303 DGMI L._. f 030 OGM-1 C:318 120 -. .MMf - C:?.14 307 279 101( ., C.312 ,-.-.