Daewoo DTF-2950-100D, Руководство по обслуживанию, Страница: 64 / 92

CP-850FX Service Manual
Europe R&D 63
5.8.2 MODE SELECTION
The TDA8946J has several functional modes, which can be selected by applying the proper DC
voltage to pin MODE.
Mute : In this mode the amplifier is DC biased but not operational (no audio output). This allows
the input coupling capacitors to be charged to avoid pop-noise. The devices is in mute mode
when 2.5 V < V
MODE
< (Vcc-1.5 V).
Operating : In this mode the amplifier is operating normally. The operating mode is activated at
V
MODE
< 0.5 V.
5.9 VERTICAL
DEFLECTION
The vertical driver circuit is a bridge configuration. The deflection coil is connected between the
output amplifiers, which are driven in phase opposition. The differential input circuit is voltage
driven. The input circuit is especially intended for direct connection to driver circuits which deliver
symmetrical current signals, but is also suitable for asymmetrical currents. The output current of
these devices is converted to voltages at the input pins via resistors R350 and R351. The
differential input voltage is compared with the output current through the deflection coils
measured as voltage across R302, which provides internal feedback information. The voltage
across R302 is proportional to the output current.
5.9.1 FLYBACK VOLTAGE
The flyback voltage is determined by an additional supply voltage V
flb
. The principle of operation
with two supply voltages (class G) makes it possible to fix the supply voltage Vp optimum for the
scan voltage and the second supply voltage V
flb
optimum for the flyback voltage. Using this
method, very high efficiency is achieved. The supply voltage V
flb
is almost totally available as
flyback voltage across the coil, this being possible due to the absence of a coupling capacitor.
5.9.2 PROTECTION
The output circuit has protection circuits for :
- Too high die temperature
- overvoltage of output stage A
5.9.3 GUARD CIRCUIT
The guard signal is not used by the video IC to blank the screen in case of fault condition.
5.9.4 DAMPING RESISTOR
For HF loop stability a damping resistor (R331 & R332) is connected across the deflection coil.
5.9.5 EAST-WEST AMPLIFIER
The East-West amplifier is current driven. It can only sink currents of the diode modulator circuit.
A feedback resistor R397 is connected between the input and output of this inverting amplifier in
order to convert the East-West correction input into an output voltage.
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