Sanyo M9998LU - Amplifier Adjustments

(3
(10)
(11)
In playback mode, the audio sources (playback
signals) detected by right and left heads are fed into
(G) and (H) by way of tape equalizer amplifier and
Dulby amplifier.
When FF-Cue/AMSS or REW-Review/AMSS button
is pushed in, switches S621, S622, or S631, S632
are closed.
Transistor Q712 amplifies the audio sources in the
AF {audio frequency) amplifier.
Capacitor C731 and resistor R730 compose a low-cut
filter in order to eliminate the low frequency compo-
nents of audio sources.
1C703 comprises circuits for AM amplifier, AC-DC
converter, comparator and others, being designed to
amplify the audio sources again, detect the level, and
form pulses.
The following waveforms are delivered to terminals
No. 2 (C, R) and No. 6 (Tr-Out).
Transistor Q706 is switched on and off due to the
differential voltage of emitter and base, composing
single-shot pulse in the collector. Times ty, ty, t3
are set by the time constant of capacitor C718 and
resistor R733.
Transistor O713 prevents erroneous actions in switch
operations in the muting circuit.
Transistors O707 and Q708 are linked by Darlington
connection, of which single-shot pulses of small
current are used to drive the plunger.
When the plunger starts to move, the stide (123) of
the mechanism is pulled, so that the FF-Cue/AMSS
or REW-Review/AMSS button locked in item (1)
will be reset.
Diode D709 is designed to prevent counter-electromo-
tive current during plunger movement.
BRAKING POINT
TAPE LEVEL r
TAPE RUNNING 9 20°00 44" =
DIREC TION
t ee [os
TERMINAL ;
Q706 EMITTER '
th 3
TERMINAL @) ‘ : Sows
M6 RAN 1
Q?06 COL LECTOR
RIGHT CHANNEL
AMP PCB
AMPLIFIER ADJUSTMENTS
Prepare
Power source ........... 02s eee eee DC 15V
Mode switch ..........00 00 eee e eee STEREO
Dolby NR/ALC switch ............006. OFF
Selector switch... 0... ee ee ee TAPE
Fape switch. eo essing ee ea all ae acts NORMAL
Loudness switch... 0... .. 2.0.00 eee eee OFF
Head azimuth
Tape to be used; (10 kHz,—10 dB)
Load a test tape and press the PLAY button.
Adjust the head azimuth screw so the LINE OUT level
becomes maximum.
Repeat the adjustment on both cahnnels and both sides of
aVIVM
MAX”
set
Adjustment of playback level
Play back Dolby test tape MTT-115 OdB (TEAC Dolby
level calibration tone 200 nWb/m).
Adjust controls SVR801 (L-ch) and SVR901 (R-ch) until
the output level from measuring test point becomes 0.58 V.
*
Measuring test point means ...
The line (common terminals of record/playback switch
of $806 and S906) on point 7 of Dolby IC (LM1011N
Dolby), 1C801, 1C901, and the ground.
LEFT CHANNEL