Luxman l 30 service manual

Page 1

SOLID STATE INTEGRATED AMPLIFIER

LMUXMMIIII

SERVICE MANUAL

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MODEL: L-SO CIRCUIT DESCRIPTION

[Power Supply]

Power supply to main amp: The power supply consists of two parts designed for supply of
power to the main amplifier and the pre-amplifier respectively. For the main amplifier driven
by a high current load, silicon diode D205 - D208 (Hi-Pi special) are used, and supply voltage
values are +35V and -35Vl

Power supply to other than main amp: Power sources other than for the main amplifier are
obtainable by D203 (luuooa) with the half wave rectification circuit and ripple filter. Supply
voltage values at each section are; equalizer stage -37V, tone control stages -27V and inter-

mediate stages -2M.5V.

[Ere Amplifier]

The pro-amplifier consists of an equalizer, an intermediate amplifier, and a tone control.
The equalizer adopts the Negative Feedback circuit using tow silicon transistors, 2SABaE (Qlol).
ZSClSRS (0102) per channel and is designed to provide proper equalization to the input signals.
Input signals given through the AUX-l, -2, and TUNER terminals bypass the equalizer and are fed
directly to the later stages of this amplifier.

Controls arranged after the equalizer stage are: REC. OUT CONNECTOR, TAPE-MONITOR SWITCH,
LOW-CUT FILTER, HIGH-CUT FILTER, HOD: SELECTOR, VOLUME CONTROL. and LOUDNESS SWITCH. The
intermediate amplifier consisting of 0103 010 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 CB-Nf-circuit of 0105. Any
desired frequency response can be adjusted by the following controls: Variable resistor VRlOl
(BASS), and variable resistor VR102 (TREBLE). Major components of the pre-amplifier are arrang-
ed on the printed circuit board PBlOOB.

[Main Amplifier]

The main amplifier is of full stage direct coupling, one stage differential amplification,
predriving and fully complementary circuits. The power transistors 0207 2SD371(NPN) and Q309
zsasaltrnr) (Z-transistor per channel) are fitted over to the heat sink inside the chassis.

All circuit components are assembled to the printed circuit board PBlOOQ. The differential
amplifier is consisted of QZOl and 0202, the pre-driving stage of 0203, and the driver transis-
tors, 0205 and 0206. Besides the above transistors, capacitors, resistors, and semi-fixed volume

controls are integrated in the circuit.

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