Author£ºUnknown
Source£ºNetwork
2015-07-04 07:49:40
Core tips£ºTC-51P700G Panasonic PJTV no image, no sound
After investigation no image, no sound fault occurs on a public channel, in particular to IC3001 intermediate frequency integration FS tuner TUNI and AV / TV, video and audio switch circuit. With TC-51P7OOG high-frequency picture in picture function and main picture can freely switch, the picture of a switch to the main screen mode, the same can not to the image, does not listen to the sound, thus exclude the suspected of TUNI TUN2, fault range reduced in AV / TV switch circuit. In order to quickly determine the fault location, the I2C bus fault self checking function of the machine is started, and the IC is checked.
In the boot state while pressing the remote control on the "HELP" channel search and the amount of the "-" key, the movement into the self-test mode, the screen displays the results shown in figure.
; white balance controller IC7702 WBDAC. Among them, MEM is EzpROM memory IC11O4; GC1 is the main common core IC; GC2 is deputy common core IC, the numbers were ICl301 ICl304: VDU is video decoding processor ICl305; GIP is CIP processor ICl303; RGB color matrix ICl315; AV / TV switch IC3001 AVSW; and TUNI is main tuner TNROOI; TUN2 is vice tuner TOO2; Daci is DAC controller ICl253; MSP is a stereo decoder IC2001; conv is digital convergence processor ic7107; CVDAC is convergent DAC controller IC7121 "OK" is normal, but "NO" is an exception.
In the control of the 13 IC, only the AV/TV switch IC3001 detection results for "NO", the other IC are "OK". Directly to find the movement of a plate on the AV / TV switch IC3001 and measurement (42) pin voltage 9.OV and measured (33) feet (SCL), (34) foot SDA port voltage, found (34) pin voltage below 2.8V, check the SDA line pull resistance and the foot series protection resistors found IC3001 (34) feet on ground resistance R3029 end pin loosening, after the replacement of the resistor fault excluded.
IC3001 the switching of audio and video signals is selected by the master microprocessor through the IIC bus to transmit the data in the chip. Before the control transfer instructions, CPU to the bus hanging controlled IC addressing (each IC presupposition has an address code) and the controlled IC response signal to confirm correct before the implementation of the key operation instruction addressing. IIC bus voltage general 3V~5.OV, if less than 3V, CPU and controlled IC can not be identified, so it is impossible to read and write operations, resulting in switching failure.