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Service Manual CP-785A
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
< (Vcc-1.5 V).
MODE
Operating : In this mode the amplifier is operating normally. The operating mode is activated at V
MODE
< 0.5 V.
5-7 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.
Flyback voltage
The flyback voltage is determined by an additional supply voltage V
. The principle of operation with
flb
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
optimum for the flyback voltage. Using this method, very high
flb
efficiency is achieved. The supply voltage V
is almost totally available as flyback voltage across the
flb
coil, this being possible due to the absence of a coupling capacitor.
Protection
The output circuit has protection circuits for :
- Too high die temperature
- overvoltage of output stage A
Guard circuit
The guard signal is not used by the TDA936x to blank the screen in case of fault condition.
Damping resistor
For HF loop stability a damping resistor (R305) is connected across the deflection coil.
EAST-WEST Amplifier (TDA8358J only)
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.
-38-
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