HITACHI 42PMA225EZ
Manual de Servicio

1. INTRODUCTION
42� Plasma TV is a progressive TV control system with built-in de-interlacer and scaler. It uses a 852*480 panel with 16:9 aspect ratio. The TV is capable of operation in PAL, SECAM, NTSC (playback) colour standards and multiple transmission standards as B/G, D/K, I/I�, and L/L´ including German and NICAM stereo. Sound system output is supplying 2x10W (10%THD) for stereo 8� speakers. The chassis is equipped with many inputs and outputs allowing it to be used as a center of a media system. It supports following peripherals: 2 SCART�s with all of them supporting full SCART features including RGB input 1 AV inputs. (CVBS+ Stereo Audio) 1 SVHS input 1 Streeo Headphone output 1 D-Sub 15 PC input 1 DVI input 1 Stereo audio input for PC/DVI Other features include, Picture-In-Picture (PIP) , Picture-And-Picture (PAP) .

2. MULTI STANDARD SOUND PROCESSOR
The MSP34x1G family of single-chip Multistandard Sound Processors covers the sound processing of all analog TV-Standards worldwide, as well as the NICAM digital sound standards. The full TV sound processing, starting with analog sound IF signal-in, down to processed analog AF-out, is performed on a single chip. These TV sound processing ICs include versions for processing the multichannel television sound (MTS) signal conforming to the standard recommended by the Broadcast Television Systems Committee (BTSC). The DBX noise reduction, or alternatively, Micronas Noise Reduction (MNR) is performed alignment free. Other processed standards are the Japanese FM-FM multiplex standard (EIA-J) and the FM Stereo Radio standard. Current ICs have to perform adjustment procedures in order to achieve good stereo separation for BTSC and EIA-J. The MSP34x1G has optimum stereo performance without any adjustments.

3. VIDEO SWITCH TEA6415
In case of three or more external sources are used, the video switch IC TEA6415 is used. The main function of this device is to switch 8 video-input sources on the 6 outputs. Each output can be switched on only one of each input. On each input an alignment of the lowest level of the signal is made (bottom of sync. top for CVBS or black level for RGB signals). Each nominal gain between any input and output is 6.5dB.For D2MAC or Chroma signal the alignment is switched off by forcing, with an external resistor bridge, 5VDC on the input. Each input can be used as a normal input or as a MAC or Chroma input (with external Resistor Bridge). All the switching possibilities are changed through the BUS. Driving 75ohm load needs an external resistor. It is possible to have the same input connected to several outputs.

4. AUDIO AMPLIFIER STAGE WITH TDA8928ST
The TDA8928ST is a switching power stage for high efficiency class-D audio power amplifier system. With this power stage a compact 2x10 W Self Oscillating Digital Amplifier System (SODA) can be built, operating with high efficiency and very low dissipation. No heat sink is required. The system operates over a wide supply voltage range from ±7.5 V to ±30 V and consumes a very low quiescent current.

5. POWER SUPPLY (SMPS)
The DC voltages required at various parts of the chassis are provided by an SMPS transformer controlled by the IC MC44608, which is designed for driving, controlling and protecting switching transistor of SMPS. The transformer generates 145V for FBT input, +/-14V for audio amplifier, 5V and 3.3V stand by voltage and 33V, 12V and 5V supplies for other different parts of the chassis. An optocoupler is used to control the regulation of line voltage and stand-by power consumption. There is a regulation circuit in secondary side. This circuit produces a control voltage according to the changes in 145V DC voltage, via an optocoupler (TCET1102G) to pin3 of the IC. During the switch on period of the transistor, energy is stored in the transformer. During the switch off period energy is fed to the load via secondary winding. By varying switch-on time of the power 1 Plasma TV Service Manual 11/01/2005