and ground SW signal, not superposing it to L/R track signal.
In reverse, when P-BURST is of high level, V100 will be switched into conduction and
SWM signal cannot be outputted from external terminal. Meanwhile, V101 is cut off and
SW signal is superposed to L/R track signal.
The burst driver of AV215T (RU) can be divided into three steps. This principle is to
change the volume of burst driver by changing the SW output volume of M62446.
Meanwhile, SWM signal is added to relay via XS9. When the relay is off, SW signal will
be grounded, disabling the output at super bass port.
III. Mixing and amplification circuit of 5.1 signal and karaoke
When L/R track signal of 5.1 signal is superposed with SW signal and amplified by
N101B/N100B, it is sent to the reverse phases of N101A/N100A. Meanwhile, OK-R/OK-L
signals are also respectively added to the reverse phases of N101A/N100A. After mixing
and amplification by N101A/N100A, they are outputted respectively from pin 1 of
N100A/N101A to power amplification circuit for power amplification.
Meanwhile, the C-1 signal sent by volume board is added to the reverse phase of pin 6 of
N102B and added to the reverse phase of N102A after amplification. Now C1-1 signal after
electronic reverberation processing is also added to the reverse phase of N102A and sent to
power amplification circuit after mixing and amplification.
SR-1/SL-1 of another volume board is also added to the reverse phases of N103B and
N104B for amplification and then sent to N103A and N104A for further amplification, and
later sent to power amplification circuit.
One way of 5.1 signal being mixed and amplified is sent to power amplification circuit
passing through XS9, and the other way forms DIST (distortion error detecting signal)
signal passing through R111-R113/R142/R145/VD100-VD104, which will be added to
CPU for automatic gain, so as to control volume output.
Section Four CPU Board
Achieve overall control, automatically search input signal and analyze spectrum
1. CPU Overall Control
N100, the overall CPU, is the overall control center, inputting all kinds of control
instructions to controlled circuits to achieve all kinds of control functions. It adopts +5V
supply with pin 40 as its supply pin. Pin 18 and pin 19 connect externally with 12M crystal
oscillator to provide working clock frequency for itself. Pin 9 is its reset pin. When starting,
+5V charges C106 via R100. The voltage of two ends of capacitance cannot be mutated,
thus B-pole of triode V100 is low level, that is, V100 conduction gives a high-level reset
signal to CPU. When capacitance C106 finishes charge, V100 stops and then reset finishes.
The form of this reset circuit is to reset high level and keep low level.
When the machine is working, the static information of start log in the screen and
Chinese characters are stored in CPU internal static memory. N101, a status memory, can
record the current working status of machine when cutting off and show the status when
next starting up, avoiding users to re-adjust. The sound mode set by users is also stored in it
and can be activated when necessary.
Ⅱ. Detect Input Signal and Automatically Search Circuits
