Sanyo M7700L - Playback Gain Adjustment; Oscillator Frequency and Recording Bias Adjustment

ELECTRICAL ADJUSTMENTS (continua)
Adjustment
4. After the adjustment, secure the screw with paint or glue.
PLAYBACK GAIN ADJUSTMENT
1.
Connect
the
two
sets
of
VTVM
to
the
R/P
DIN
socket
as
illustrated
and
insert
the
1
kHz
test
tape
(Example:
TEAC
MTT-112B) into the compartment.
REC
VTVM B
Dummy Load
470 k-ohm 470 k-ohm
RIGHT CHANNEL
2. Check to see that the output of the right channel is 0.65 V
(£0.1 V) with the unit in the playback mode.
3. If necessary, ground the resistor R108 and/or R109 by
soldering the pattern to obtain the specified output as
illustrated.
Q303
LEFT CHANNEL
4. Adjust the output by grounding or separating the resistor
R208 and/or R209 with the same method as RIGHT
CHANNEL.
5. After the adjustment, check that the output difference
between the right channel and the left channel is within 2 dB.
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R203 |
OSCILLATOR FREQUENCY AND RECORDING BIAS
ADJUSTMENT
RIGHT CHANNEL
1. Connect the VTVM across R103, and the frequency counter
to the output terminal of the VTVM as illustrated.
VTVM
3.8mV — 4.3mV
Frequency Counter
48.85kHz — 48.95kHz
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TS) Os dae
Q303
2. Set the unit in the recording mode. Then, adjust the
frequency by turning the core of the oscillator transformer
(T301) with an alignment tool until the frequency counter
reads 48.85 kHz — 48.95 kHz.
3. Adjust the potentiometer (P101) with the unit in the
recording mode until the VTVM reads 3.8mMV —43 mV
(380 nA — 430 pA).
LEFT CHANNEL
Connect the VTVM_~ across R203. Then, adjust the
potentiometer (P201) until the VTVM reads 3.8 mV — 43 mV
(380 pA ~— 430 pA).
VTVM
3.8mV — 4.3mV