Marantz 2600 - Stereo Separation Alignment; Muting Circuit Alignment

oscillator coil L106 to obtain maximum audio output.
. Set the signal generator to 109 MHz and provide about
3 to 5yuV output. Rotate the tuning knob and place the
tuning pointer at the high frequency end and adjust the
trimming capacitor C123 for maximum output.
. Repeat steps 2 and 3 until no further adjustment is
necessary.
. Set the signal generator to 90 MHz and tune the receiver
to the same frequency. Decrease signal generator output
until the audio output level decreases with the decreas-
ing generator output. Adjust the antenna coil L101, RF
coils L102, L103 and L104 and IF transformer L105 for
minimum audio distortion.
. Set the signal generator to 106 MHz and tune the receiv-
er to the same frequency. Adjust the trimming capacitors
CFO1, CFO2, CFO3 and CF04 for minimum distortion.
. Repeat steps 5 and 6 until no further adjustment is
necessary.
. Connect a VTVM (at DC 1 V range) across the J204 and
J205, Adjust the secondary core (upper) of discrimina-
tor transformer £201 so that the VTVM indicates null
reading (zero reading) at no signal. Set the FM signal
generator to 98 MHz and increase its output level 1 kuV
and tune the receiver to the same frequency so that the
VTVM gives null reading. Adjust the primary core
(lower) of L201 for minimum distortion. (Scope.display
can, of course, be used as tuning indicator instead of the
VTVM, if the scope unit has been correctly adjusted as
instructed in the “Scope Display Adjustment’’.)
. Set the signal generator to 98 MHz at 100 kuV, and
adjust R278 so that the signal strength indicator spot
just reaches upper mark.
4.2 STEREO SEPARATION ALIGNMENT
1.
Set the FM signal generator to provide.1 kuV at 98 MHz.
Tune the receiver to the same frequency so that the
center tuning indicator spot indicates its center.
. Turn the signal generator modulation off (with the pilot
signal turned off), connect a frequency counter to test
point J238, and adjust R310 so that the frequency
counter may precisely read 19 kHz.
. Modulate the signal generator with stereo composite
signal consisting only of subchannel signal (of course a
pilot signal must be included).
. Adjust the trimming resistor R319 for maximum and
same separation in both channels.
4.3 MUTING CIRCUIT ALIGNMENT
1.
2.
Set the FM signal generator to provide 6 uV at 98 MHz
and tune the receiver to the same frequency correctly.
Depress the FM MUTING pushswitch, Set ROO1 to MIN
Position (counterclockwise). Adjust R330 until the mut-
ing circuit is activated to produce output for exactly
6 LV input.
. In turn increase the FM signal generator output up to
50 UV.
. Set ROO1 to MAX position (clockwise). Adjust R347
until the muting circuit is activated to produce output
for exactly 50 uV input.
. Turn ROO1 from MIN to MAX to assure the muting
threshold level can change in the range of 6 to 50 uV.
6.
Adjust ROO1 until the muting threshold level is 12.5 V.
Then, increase the FM signal generator output up to
1 kuV and shift its frequency up and down. Note both
up- and down-shifted frequencies at which undesirable
audio side responses are muted out. Adjust R280 until
the muting circuit is activated when the oscilloscope
trace deflects 10 to 20 mm.
. Turn on QUARTZ Lock pushswitch and observe the
QUARTZ LED which synchronize with the muting
circuit.
4.4 DOLBY FM TAPE OUTPUT SETTING
1.
2.
Set the modulation of FM signal generator to 400 Hz,
50% (+37.5 kHz Dev.).
Set the signal generator to provide 1 kuV at 98 MHz.
Tune the receiver to the same frequency so that the
center tuning meter pointer indicates its center.
. Set the SELECTOR switch to the FM 25uS position.
Set the trimming resistors RCO1 and RCO2 so that the
output of the TAPE MONITOR OUT jacks R and L
become 580 mV at VTVM.
. AUDIO ADJUSTMENT
. Voltage adjustment
Connect a DC voltmeter across the pins 4 and 3 on J805.
Adjust the trimming resistor R819 until the DC volt-
meter reads 32 V.
. Main Amplifier DC off-set alignment
Connect a DC voltmeter with 0.5 or 1 V range between
the speaker terminals and adjust the trimming resistor
R760 for “zero”’ DC output on the meter. Repeat the
same procedure for the other channel.
NOTE: During this alignment no load should be connected
to the speaker terminals.
. Idle current adjustment
Connect a DC voltmeter (in 50 mV range) across TP1
and TP2 on JX01. Adjust R761 on the P.W. board on
the left side of the tunnel heatsink until the veltnneter
reads 25mV (32 mA). In turn, connect the vetnreter
across TP3 and TP4 on JX02 and similarly, adjut FR716
on the P.W. board on the right side of the tunrel heat-
sink until the voltmeter reads 25 mV (32 mA).
. Check DC off-set voltage aligned in the procedue 3 and
if any DC output is observed on the DC voltmete, acijust
the R760 again for ‘‘zero’’ output.
CAUTION: CONTINUOUS POWER OUTPUT TESTS-
Continuous sine wave tests at high audio powe levels
impose a maximum loading condition for the powersup ply,
particularly when testing with 4 ohm output loads,ancd far
exceeds power supply loading encountered with grogram
materials. A primary line fuse has been selected for the
Model 2600 which will open if the following 4 ohmtesting
periods are exceeded:
A. At rated power of 400 watts per channel.
Testing period- 20 minutes max.
B. At power levels above 400 watts per channel.
Individual tests- 1 minute max.