Scott-631-Service-Manual 电路图 维修手册.pdf

RadioFans.CN 收音机爱 好者资料库 Scott . where innovation is a tradition SCOTT H. H. Scott, Inc. 111 Powdermill Road, Maynard, Mass., 01754 SPECIFICATIONS TUNER (FM-MPX) Usable Sensitivity (I HF) Cross Modulation Rejection Signal to Noise Ratio Total Harmonic Distortion Frequency Deviation (Drift) *Frequency Response Capture Ratio Selectivity Tuning Range Accuracy of Calibration Separation FM ctave: -3 db 5 kHz +12 db SO Hz + 4 db 10 kHz 32.5 watts 25 watts 18 watts 18 watts Form D-342-B/382-B-2W RadioFans.CN 收音机爱 好者资料库 - AUDIO TEST Total Harmonic Distortion Frequency Response Power Bandwidth at Rated Distortion (IHF Method) Hum and Noise (Phono) Range of Line Voltage and Frequency Power Consumption -117 v at 60 Hz (AC only) EQUIPMENT NEEDED Audio Oscillator VTVM Oscilloscope VOM Load Box Attenuator Distortion Meter Variac AC Supply Fixture Set Controls to the Following: Input Selector Stereo Switch Tone Controls Loudness Stereo Bal. Sw. Noise Filter Speaker Switch Power Switch Extra Stereo Flat O Min. Norm. OUT ON OFF 1.Bias and Balance Settings and Voltage Checks 0.8% 18-25,000 1 db 25-20,000 Hz -55 105-120v, 50-60 Hz 25-95 watts Turn unit on - watch carefully for any signs of voltage shorts. With bias pots (lK) still full ccw (from top of unit), check supply for 48 to 50. Adjust bias pots for 0.8 mA current from each test point in the rear of the unit to ground. 2. Check power supply board Check power supply board Sensitivity Check for 25V +10% for 12V +10% Audio osc. to EXTRA at .3V (+2 dB) input. Connect 8 ohm load to main speaker taps. Turn loudness pot to max., observe output of 18 watts (12V). Check tape output jack with troubleshooting lead for same output as signal. 3. Distortion Check At 12V output max. distortion 0.6%. 4.Tape Monitor Switch Check Audio osc. to EXTRA at .3 input to L channel. Note output at left channel speaker terminal. Put tape monitor switch in the IN position. Note loss of output. Connect input cable from L channel tape out to L channel tape in. Note restoration of signal out. Repeat process for R channel, then return tape monitor switch to out position. 2 RadioFans.CN 收音机爱 好者资料库 TUNER-AM SECTION 1.Switch tuner to AM position, output from tape output jack. 2.Connect signal generator at 455 kHz through .05 capacitor to green lead from AM TEST If board to feedthrough terminal in front end. Clip ground lead to chassis. Remove RF transistor. 3.Peak IFs and detector for maximum A.G.C. (tuning meter indication) of audio noise output, using no modulation. Final peaking should be done with 20 uv from generator with output level of 100 mv :!:2 dB. 4.Remove signal generator coupling to IFs, connect generator to external antenna terminals. Install RF transistor. 5.Tune oscillator coil to 600 KHz and oscillator trimmer to 1600 kHz. Tune RF trimmer at 1400 KHz, and antenna slug at 800 KHz. Seal antenna core. 6.Repeat Step 5 until unit is aligned and max. output at given frequencies has been achieved. Calibrate: 590 KHz +10 KHz 850 KHz 1030 1510 (tol. 20 KHz) 7. Check signal-to-noise at 600 KHz, 100 uv for 10 dB, at 1400 KHz, 10 uv for 10 dB. 8.Remove generator connection from external antenna terminals, loop around low end of loop antenna using 47 ohm resistor, and at 1400 KHz peak antenna trimmer. 9.Check output level left and right tape jacks, at 100 uv output should be 250mv +2 dB, 10.With phones, check for AM calibration, oscillation, harmonic pickup, etc. 11.Wrth AM tuned to low end of band, set meter adjust control so meter reads O. Switch to FM and note little or no change max. difference between AM and FM across band, 2 meter divisions. 7 FRONT END ALIGNMENT FM FRONT END ALIGNMENT FOR FM SECTION 1.Connect RF generator to the antenna terminals with the following adaptations: FROM GEN. 270Jt ._ . ._ _ TO GND. 2.Set RF generator and FM tuning dial to 92 mHz. Generator output should be about 6 uv. Peak 1205, 1204 and 1201 for maximum audio output. 3.Set generator and FM tuning dial to 106 mHz. Peak RF trimmer and mixer trimmer. 4.With about 3 uv from FM generator, repeat procedure until no further output is obtained. Signal should look like this: 5.The only time that the oscillator mixer and trimmer should be touched is if the calibration is out of specification. 8 FM ANT. Z-AMLFM-8 FRONT END FM OSC HIGH QZ.03c; FM b rg AM L C60f 1.0 Bt12V AM AGC +12 AM OUT AM LOW 10.7 MHz l0.7 MH2 c:202H9J.-tl-+-M-E-TE_R _ b Q2.01 GNC. DRIVE )( J:t I LOWFNI RF HlGH AM 300.R GNO. FM 68 METER DRIYE IF OUT R602 33K , 10.7 MHz MIX.HIGH MIX. LOW OSC.HIGI-I OSC.LOW Z-FM-15 _ .,. _ FRONT END AGC IF C e +12v Q202 :4 9 FRONT END -B Mechanical layout of Front Ends denoting, Osc i I la tor, Mixer, Antenna Coils and Voltages present under nor mal operating conditions -B - 11 F STRIP I r- 1 I I s 10-Hz:-<F-VVr-tH TUNING METER 21 C30.5 .05 AM A.G.C _ _. ._. _ _ I I I I I I L 3 T301 t2VOC AM IN 10.7MHz IN C303 .02 G8 1 R 3 0 5 C306 6 - AUX. A.G.C. R30 i?70 7 12VDC T303 ,r;f C312 470 -t T.104 R311 R316 150K 3K - Wv- 8 9 t2VDC L-JUMPER- ALL VOLTAGES POSITIVE DC15% MEASURED WITH 20 K ohm/V VOM AND 117 VAC LINE. FM VOLTAGES MEASURED WITH 300 OHM LOAD ON EXTENAL FM ANTENNA TERMINALS. TUNER OFF-STATION. INPUT SWITCH IN FM POSITION. AM VOLTAGES MEASURED WITH LOOP ANT ENNA, TUNER OFF-STATION, INPUT SWITCH IN AM POSITION. Q301, Q302 - QSE1002 AM -FM I.F.