Marantz 2250-B Service Manual

3. AM ALIGNMENT PROCEDURE (~

3.1 AM IF 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 transformer L153 for maximum height and flat top symmetrical
response.

3.2 AM Frequency Rangeand Tracking Alignment

1. Set AM signal generator to 515 kHz. Turn the tuning capacitor fully closed (place the tuning
pointer at the low end) and adjust the oscillator coil L152 for maximum audio output.

2. Set the signal generator to 1650 kHz. Placethe tuning pointer in the high frequency end and
adjust the oscillator trimmer on the oscillator tuning 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 slug
core of AM ferrite rod antenna and RF coil L151 for maximum output.

5. Set the generator to 1400 kHz and tune the receiver to the samefrequency and adjust both
trimming capacitors 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 output as necessaryto avoid AGC

action.

3.3 AM Signal Strength Meter Alignment
Set an AM signal generator to 1000 kHz at 5k1-N, and adjust R178 so that the signal
strength meter may read90% of the full scale.

4. FM ALIGNMENT PROCEDURE

1. ,Connect an FM signal generator to the FM ANTENNA terminals and an oscilloscope and an
audio distortion analyzer to the 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 low
frequency end by rotating the tuning knob and adjust the core of oscillator coil L104 to

obtain maximum audio output.

3. Set the FM SG to 109 MHz and provide about 3 to 5J.1.Voutput. Rotate the tuning knob and

place the tuning pointer at the high frequency end and adjust the trimming capacitor C106

for 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. Decreasesignal
generator output until the audio output level decreases with the decreasing generator
output. Adjust the antenna coil L101, RF coils L102 and L103 and IF transformer L105 for

minimum 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 and C105 for minimum distortion.

7. Repeat steps 5 and 6 until no further adjustment is necessary.

8. Adjust the secondary core (upper) of discriminator transformer L201 sothat the center tun-
ing meter pointer indicates its center at no signal applied. Set the FM SG to 98 MHz and

,

1

increase its output level I kJ.l.Vand tune the receiver to the samefrequency sothat the center
tuning 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 sothat the signal strength meter
may read 90% ofthe full scale.

3

5. STEREO SEPARATION ALIGNMENT

1. Set the FM SG to provide I kj.LVat 98 MHz. Tune the receiver to the samefrequency sothat
the center tuning meter pointer indicates its center.

2. Turn the FM SG modulation off (with the pilot signal turned off), connect a frequency
counter to test point J310, and adjust R311 so that the frequency counter may precisely

read 19 kHz.

3. Modulate the FM SG with stereo composite signal consisting only of subchannel signal (of
course a pilot signal must be included).

4. Adjust the trimming resistor R301 for maximum and same separation in both channels.

6. MUTING CIRCUIT ALIGNMENT

1. Connect a VTVM across the resistor R363 and adjust the resistor R363 until the meter
reads0.75V DC at no signal.

2. Set the FM SG to provide I kJ1Vat 98 MHz and tune the receiver to the same frequency
correctly.

3. Turn on MUTI NG push switch. Shift the FM signal generator frequency to plus and minus

and note both plus and minus shifted frequencies at which undesirable audio side responses
are muted out. Adjust the R363 so that the same shifted frequencies mute the undesirable

side response.

4. Adjust R362 for proper frequency shift at which the muting circuit operates.

7. DOLBY FM TAPE OUTPUT SETTING

1. 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 so

that the center tuning meter pointer indicates its center.

3. Turn on DOLBY FM push switch. Set the semifixed resistors RC01 and RC02 so that the
output of the TAPE OUTPUT terminals Rand L become 580 mVat VTVM.

8. AUDIO ADJUSTMENT

1. Voltage adjustment
Connect a DC voltmeter between pin terminal 804 and 805, and adjust the trimming

resistor R806 for 35V DC.

2. Main Amplifier DC off--setalignment
Connect a DC voltmeter with 0.5 or 1 V rangebetween the speakerterminals and adjust the

trimming resistor R707 for "zero" DC output on the meter.

Repeat the sameprocedure for the other channel.

Note: During this alignment no load should be connected to the speakerterminals.

3. Idle-current adjustment
Connect a VTVM between pin terminals 708 and 710. Next, adjust the trimming resistor

R719 sothe VTVM reads10mV DC. Repeat the sameprocedure for the other channel.

4. Check DC off-set voltage aligned in the procedure 2 and if any DC output is observed on the
DC voltmeter, adjust the R707 again for "zero" output.

5. Phono-amplifier adjustment
Connect an oscilloscope to the TAPE OUT jacks and an audio signal generator to the
PHONO jacks. Placethe selector switch in the PHONO position. Increase1 kHz audio signal

gradually until a slight clipping on top of the sine-wave is observed on the oscilloscope.

Adjust the trimming resistor R408 for equal clipping level.
For the other channel adjust R409.

4

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