Marantz-2250B-rec-sm 维修电路原理图.pdf
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1、RadioFans.CN 收音机爱 好者资料库3.AM ALIGNMENTPROCEDURE(3.1AMIF Alignment()1. Connect a sweep generator to the J 153 and an alignment scope to the test point B.2. Rotate each core of IF transformerL153 formaximum height and flat top symmetricalresponse.3.2AMFrequency Rangeand Tracking Alignment1. Set AM sign
2、al generator to 515 kHz. Turn the tuning capacitor fully closed (place the tuningpointerat the low end) and adjust the oscillatorcoilL152 for maximum audio output.2. Set the signal generator to 1650 kHz. Placethe tuning pointer in the high frequency end andadjust the oscillator trimmer on the oscill
3、atortuning capacitor for maximum audio output.3.Repeat steps 1 and 2 until no further adjustment is necessary.4. Set the generator to 600 kHz and tune the receiver to the same frequency anq adjust a slugcore of AM ferrite rod antenna and RF coil L151 for maximum output.5. Set the generator to 1400 k
4、Hz and tune the receiver to the samefrequency and adjust bothtrimmingcapacitors of antenna and RF tuned circuit for maximum output.6. Repeat steps 4 and 5 until no further adjustment is necessary.Note:During tracking alignment reduce the signal generator outputas necessaryto avoid AGCaction.3.3AM Si
5、gnal Strength Meter AlignmentSet an AMsignal generator to1000 kHz at 5k1-N, and adjust R178 so that the signalstrength meter may read 90% of the full scale.,134.FM ALIGNMENTPROCEDURE1. ,Connect an FM signal generator to the FM ANTENNAterminals and an oscilloscope and anaudio distortionanalyzer to th
6、e TAPE OUTPUT jacks on the rear panel.2. Set the FM SG to 87 MHz and provide about 3 to 5J.1.V. Placethe tuning pointer at the lowfrequencyend by rotating the tuning knob and adjust the core of oscillator coil L104 toobtain maximum audio output.3. Set the FM SG to 109 MHz and provide about 3 to 5J.1
7、.V output.Rotate the tuning knob andplace the tuning pointer at the high frequency end and adjust the trimming capacitor C106for maximum output.4.Repeat steps 2 and 3 until no further adjustment is necessary.5. Set the FM SG to 90 MHz and tune the receiver to the same frequency. Decreasesignalgenera
8、toroutputuntilthe audio outputlevel decreases withthe decreasing generatoroutput.Adjust the antenna coil L101, RF coils L102 and L103 and IF transformer L105 forminimum audio distortion.6. Set the FM SG to 106 MHz and tune the receiver to the same frequency. Adjust the trim-ming capacitor C102, C104
9、 and C105 for minimum distortion.7. Repeat steps 5 and 6 until no further adjustment is necessary.8. Adjust the secondary core (upper) of discriminatortransformerL201 sothat the center tun-ing meter pointerindicates its center at no signal applied. Set the FM SG to 98 MHz andincrease its output leve
10、l I kJ.l.V and tune the receiver to the samefrequency sothat the centertuning meter pointer indicates its center.Adjust the primary core (lower) of L201 for minimum distortion.9. Set the FM SG to 98 MHz at 1000 kJ.l.V,and adjust R374 so that the signal strength metermay read 90% ofthefull scale.Radi
11、oFans.CN 收音机爱 好者资料库5.STEREO SEPARATIONALIGNMENT1. Set the FM SG to provide I kj.LVat 98 MHz. Tune the receiver to the samefrequency sothatthe center tuning meter pointer indicates its center.2. Turn the FM SG modulationoff(withthe pilotsignal turned off), connect a frequencycounter to test point J31
12、0, and adjust R311 so that the frequency counter may preciselyread 19 kHz.3. Modulate the FM SG with stereo composite signal consisting only of subchannel signal (ofcourse a pilot signal must be included).4. Adjust the trimmingresistor R301 for maximumand same separation in both channels.6.MUTINGCIR
13、CUITALIGNMENT1. Connect a VTVMacross the resistor R363 and adjust the resistor R363 untilthe meterreads0.75V DC at no signal.2. Set the FM SG to provide I kJ1Vat 98 MHz and tune the receiver to the same frequencycorrectly.3. Turn on MUTI NG push switch. Shift the FM signal generator frequency to plu
14、s and minusand note both plus and minus shifted frequencies at which undesirable audio side responsesare muted out. Adjust the R363 so that the same shifted frequencies mute the undesirableside response.4. Adjust R362 for proper frequency shift at which the muting circuit operates.7.DOLBYFM TAPE OUT
15、PUT SETTING1. Set the modulation of FM SG to 400 Hz, 50% (37.5 kHz Dev.)2. Set the FM SG to provide 1 kJ1Vat 98 MHz. Tune the receiver to the same frequency sothat the center tuning meter pointer indicates its center.3. Turn on DOLBY FM push switch. Set the semifixed resistors RC01 and RC02 so that
16、theoutput of the TAPE OUTPUT terminals Rand L become 580 mVat VTVM.8.AUDIOADJUSTMENT1. Voltage adjustmentConnect a DC voltmeterbetween pin terminal804 and 805, and adjust the trimmingresistor R806 for 35V DC.2. Main AmplifierDC off-setalignmentConnect a DC voltmeter with 0.5 or 1 V range between the
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