Panasonic EURO 4 Chassis, Техническое руководство

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As with the centre channel the surround channel also
requires an additional amplifier. Again this can be
supplied by the C-Board or external amplifier.
The surround channel which is output from pin 24 of
IC2401 is fed via buffer transistor Q2403 and resistor
R2410. Here the signal splits into the following paths.
:
Those models which are able to process the
surround sound signal internally without the use of an
external amplifier, does so on the C-Board which
contains the required amplifier.
The surround sound signal which is fed to the
C-Board is fed via C2463, C2484 to the buffer
transistor
Q2423 , which has a muting transistor
Q2422 in its base.
The surround sound signal fed from Q2423 is then fed
via connector K5 pin 1 to connector C2 pin 1 and to
IC2704 (again discussed in section 25.4.).
:
The surround signal to be output to an external
amplifier and for those models with no C-Board, the
surround signal is fed via
Q2404 , where the surround
signal now splits into two paths.
The first path feds the surround audio signal now
referred to as surround left to pin 10 of
IC2402 where
once again the audio signal is amplified and buffered
and output via pin 8 of
IC2402 .
This left surround signal is then fed to the phono
output terminal JK2401.
The second path from the emitter of
Q2404 now feeds
the surround audio signal (now referred to as the right
surround audio signal) via two transistors
Q2405 and
Q2406 . Here the audio signal is amplified and
inverted by Q2405 and then buffered by Q2406 .
With the right surround audio signal inverted, the two
surround channels are now out of phase.
The right surround audio signal from the emitter of
Q2406 is then fed to the phono output terminal
JK2401.
At the output of the phono terminal JK2401 both left
and right surround audio signals are fed to an
externally connected amplifier.
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The Super 3D Bass which is output from pin 27 of
IC2401 is fed to the buffer transistor Q2426 , where
the signal is fed via a low pass filter made up of
R2508 / C2467. Here only the low frequencies, used
for bass reproduction are fed via Q2428 , which
again has a muting transistor Q2427 in its base. The
Super 3D Bass signal is then fed via connector K5
pin 5 to the C-Board via connector C2, after which
the signal is then fed to
IC2702 .
24.6. K-Board Supply Voltage
To carry out the audio processing just described on
the K-Board a 5V and 12V supply are used. These
supplies being fed via connector K2 with 5V being
fed via pin 5 and the 12V supply fed via pin 7.
The 12V supply fed to the K-Board is also used to
produce an 8V supply which is fed to pin 1 of
IC2403 which produces a regulated and stabilised
8V supply output via pin 2. This 8V supply is used
primarily for the Dolby Pro Logic Processor IC
DPL3519
IC2401 .
The 12V supply itself is used to supply IC2402 via
pin 4 and the headphone amplifier IC IC2404 via pin
8. This 12V supply however is firstly fed via
transistor
Q2407 which is used to provide a soft start
and stop of the supply to the aforementioned ICs.
The 12V supply which is fed to the base of Q2407
via R2421 at switch ON charges C2406 first, as the
charge on C2406 rises so
Q2407 begins to conduct.
As Q2407 begins to conduct so the 12V supply also
fed via D2401 to the collector of Q2407 begins to
flow via the collector / emitter junction, which begins
to charge C2407 and slow the rise of the 12V line to
IC2402 and IC2404 .
At switch OFF as the 12V line falls rapidly the
charge held in C2406 and C2407 slows this fall as
the capacitors discharge.
24.7. Headphone Output Processing
The audio signals output from the MSP IC2101 pins
21 and 22 (on Dolby models ONLY) are used for the
headphone output. These signals are independently
controlled from the main bass, treble and volume
control. The audio signals fed from the MSP
IC2101
are then fed to the K-Board via connector K7.
The audio signals are then fed to the headphone
amplifier IC
IC2404 pins 3 (L) and 5 (R), where the
audio signals are amplified and output from pins 1
and 7 and fed to connector K8 where the signals are
fed to the headphone terminal.