![](/images/new-backgrounds/1126024/126024117x1.webp)
Service manual
The TDA894xJ 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
Operating : In this mode the amplifier is operating normally. The operating mode is activated at VMODE < 0.5 V.
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 R398, which provides internal feedback information. The voltage across R398 is proportional to the output current.
The flyback voltage is determined by an additional supply voltage Vflb. 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 Vflb optimum for the flyback voltage. Using this method, very high efficiency is achieved. The supply voltage Vflb is almost totally available as flyback voltage across the coil, this being possible due to the absence of a coupling capacitor.
The output circuit has protection circuits for :
-Too high die temperature
-overvoltage of output stage A
The guard signal is not used.
For HF loop stability a damping resistor (R331) is connected across the deflection coil.
The