Luxman r 1050 service manual

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371056

SERVICE MANUAL

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CIRCUIT DESCRIPTION

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[POWER SUPPLY]

The AC line is connected to the primary side of power transformer via a two pole
power switch (front panel) and a voltage selector. Four windings are provided for the secondary
aide i.e. (l) The 12V AC is utilized for 4 pilot lamps, and is at the same time half-wave
rectified by D105 to realize DC 13V for the muting circuit and the blinker circuit. (2) 15V AC
for tuner section: This 15V AC is falf-wave rectified by D107 to obtain 18V unsmooth DC, which
is further regulated by transistor 0113 and zener diode D108 to realize 13V regulated DC against
:20% AC line. (3) 35V AC for preamp (equalizer stage, intermediate stage and tone control): The
35V AC is flaf-wave rectified by D108 to obtain -uuv unsmooth DC, which is turned into low noise
-uov DC via ripple filter 0118. Actual supply voltage at each section is; equalizer stage -37V,
tone control -27V, intermediate stage -2u.5v, all of which are determined by the voltage-drop at
the de-coupling circuit placed in each stage. (u) 36V x 2 AC for main amp.: The 36V x 2 AC are
rectified by D001 - DOOH and then led to large filtering capacitors C006 and C007 (10000uF x 2)
to obtain dual supply +48V and -u8V. (5) 21V x 2 AC for Peak Indicator, which are tapped out from

the same winding of the above (u). The 21V x 2 AC are rectified by D603 ~ D606 to obtain dual
supply +27V and *27V.

[PRE AMP SECTION]

The preamplifier consists of an equalizer, and intermediate amplifier, and a tone
control. The equalizer adopts the Negative Feedback circuit using two silicon transistors, 2SA836
(0101), 2SC1345(0102) per channel and is designed to provide proper equalization to the input

signals. Input signals given through the AUX and TUNER section bypass the equalizer and are fed
directly to the later stages of this amplifier.

Controls arranged after the equalizer stage are: REC. OUT connector, TPAE MONITOR
SWITCH, DUBBING SWITCH, LOW-CUT FILTER, HIGH-CUT FILTER, MODE SELECTOR, VOLUME CONTROL, and
LOUDNESS SWITCH. The intermediate amplifier consisting of 0301, 0302 is a flat amplifier adopting
2~stage Negative Feedback circuit which is designed to boost the equalizer, tuner or AUX. This
covers sufficiently the insertion loss by the tone control in the next stage and leads low
impedance output to the tone control for its smooth function. The tone control adopts the EB-NF
circuit of 0201 and 0202. Any desired frequency response can be adjusted by the following controls:
Variable resistor VR202 (Bass), and variable resistor VR201 (Treble). Major components of the
preamplifier are arranged on the printed circuit boards PB1059-1061, 106M. (PBlO64 for equalizer,
PB1059 for Filters, Loudness and Mode, PBlO60 for Flat Amp, PBlO6l Tone Control)

[MAIN AMPLIFIER]

The main amplifier is of full stage direct coupling, two stage differential amplifi-
cation, predriving and fully complementary circuits. The power transistors 0109 280388A (NPN) and
0110 2SB501A (PNP) (2-transistor per channel) are fitted over to the heat sink inside the chassis.
All components are assembled to the printed circuit board PBlOB2. The differential amplifier is
consisted of 0101 and 0102, the pre-driving stage of 0103, 010M, 0105 (0103 6 0104 are for the
differential amp, and 0105 is arranged for the active load of 0103), and the driver transistors,

0107 and 0108. Besides the above transistors, capacitors, resistors, and semi~fixed volume controls

are integrated in the circuit.