HITACHI C28WF53NIRISH
Manual de Servicio

Horizontal and Vertical Synchronisation Connections
Pin 20 is the vertical synchronisation input from the deflection stage. This input is used for OSD vertical synchronisation. When the TV is in the standby state, this input is normally low. The vertical input is triggered on the rising edge (positive polarity). A failure of the signal at this input when the TV is powered up will cause the TV to go to standby and fault code 0004 to be set. Pin 19 is the horizontal synchronisation input from the deflection stage. This input is used for OSD horizontal synchronisation. When the TV is in the standby state, this input is normally low. The horizontal input is triggered on the rising edge (positive polarity). A failure of the signal at this input when the TV is powered up will cause the TV to go to standby and fault code 0003 to be set.

General Input Connections Headphone Input
Pin 26 is used to detect if the headphone has been inserted into its socket. This input is normally high unless the headphone has been inserted; in which case it is near 0V. When the headphone is inserted, the loudspeakers (and internal sub-woofer if available) in the television are automatically muted.

Protection Input
Pin 21 is used to determine if a protection fault has occurred on the chassis. This line is connected to various sensing points in the power supply and deflection stages. This line is normally high unless a fault has occurred; in which case it is near ground potential.

Power-Good Input
Pin 23 is used to indicate if the power has been removed from the TV. This input normally has a mains frequency square wave, which is monitored by the software in the microcontroller. If a failure of this signal occurs when the TV is powered up, the audio power amplifiers are muted and the television begins to power-down into standby. If a brief interruption of the mains supply occurs, the TV will enter the standby condition temporarily before powering back up a few seconds later.

DTT Fan Fail Input
Pin 25 is used only on an IDTV model fitted with a DTT module. It is used to indicate if a fault in the fan on the DTT unit has occurred. This input is normally HIGH unless a fault condition has been detected (0V).

Front Panel Buttons and SAV3 Socket Inputs
Pins 15 and 16 are 2 of the 4 ADC inputs of the microcontroller. Pin 16 is connected to the Volume +/- buttons and the SAV3 (Hi-8) socket on the front panel of the TV. When the voltage on this pin is changed to a value in a certain window, the microcontroller will interpret it as either a volume up, volume down and/or an SVHS Hi-8 connector was inserted into the Hi-8 socket. Pin 15 is connected to the Programme +/- and Menu buttons on the front panel of the TV. When the voltage on this pin is changed to a value in a certain window, the microcontroller will interpret it as either a programme change or the menu button was pressed.

Analog Inputs
Pin 17 (ADC2) is the analogue input shared between the tuner AGC feedback voltage input and the scart 4 pin 8 voltage input. The selection of input is made by I304 controlled by the ADC_SEL pin (I003 pin 2). Pin 18 (ADC3) is the analogue input shared between the tuner scart 1 pin 8 voltage input and the scart 2 pin 8 voltage input. The selection of input is made by I304 controlled by the ADC_SEL pin (I003 pin 2).