TOSHIBA 15VL34
Manual de Servicio

A keypad connector (S507) is provided which utilizes the integrated low bandwidth ADC in gm2221 for scanning 5-6 keys (menu,V+,V-,P+,P- keys standard- source key optional) on the keypad. The keypad allows access to the OSD without using the remote IR controller. The L5-A board also has In System Programming (ISP) capability for the external flash ROM using DDC2Bi. This can be done using the D-Sub 15 (PC) connector on the board. ISP can also be performed using G-probe through the RS232 interface. One channel of the dual channel FET power switch (U602) is used to control the power sequencing to the LCD panel. Depending on the type of the panel, the input voltage to this FET device can be chosen as shown below: For +3.3V panels For +5V panels For +12V panels J601 is soldered on the main-board J600 is soldered on the main-board J603 is soldered on the main-board

An LM2576, a step-down regulator IC (U600), is used to generate the main +5V_STBY voltage on the board. This IC can deliver up-to 3 Ampers of 5Volts. There is no stand-by control for this regulator, which means this IC is always on, as soon as power is supplied to the board. U603(+3.3V_STBY) and U605 (+1.8V_STBY) linear regulators are used to supply the voltage necessary for the GM2221 IC and some peripherals. These voltages are also available in stand-by mode to power the microprocessor inside gm2221, LED, IR receiver IC and EEPROM. These devices are necessary to wake up the board from stand-by state. Second channel of the dual channel FET power switch (U602) is used to control cut some voltages in stand-by mode. These voltages are +5V, +3.3V and +2.5V. These voltages are used by the video processor (VPC 3230D), audio processor (MSP 34x0G), teletext processor (SDA5550), tuner and some peripheral IC�s and circuitry. In order to limit the stand-by power consumption, these voltages are not available in stand-by mode. Also the audio amplifier (TDA1517) is also in its stand-by mode using its dedicated stand-by pin. The board employs MSP3410G, a multi-system audio processor solution from Micronas. The system supports 4 audio input ports, one of which is not used on the L5-A board. Audio output is provided with speaker and headphone jacks (S409, S401) provided on the board. The sound IF signal from the tuner is connected to the audio processor directly.