A maintenance case about CANTV V50sd160 mainboard can not boot

Model: CANTV V50SD160
Version: CV828H-Z
Chip scheme: MSD6A828+single EMMC
Malfunction: The red light was on, but could not boot
Analysis and maintenance: Powered on the red indicator light was on, pressing and remote control could not turn on the TV, the printing information was as follows:

The printing information was repeated all the time, and from the printing information, it should be that the boot was not working properly. Checked the power supply of the hardware, standby 5V, standby 3.3V, all were normal. EMMC power supply was also normal. The kernel power supply had a slight jump from 1.03 to 1.09, and the DDR power supply 1.5V, normal. Cut off the power, measured the positive and negative resistance of each power supply to the ground was normal. Tear down the EMMC and wrote in the mass-production software, installed back but the malfunction was the same. So eliminated software problems and focused on the boot running condition.The two DDR chips on the left side of the main chip ran boot. If it still could not solve the problem, then check the main chip. These two DDR address lines were reused, and the data lines were used separately. Removed the MU1 first. Measured the ground resistance value one by one according to the DDR pin function diagram, and the resistance value was infinite when the DQ13 was measured, as shown in the figure below:

The normal resistance value was shown in the following figure:

Following the line inspection, it was found that the perforation under the chip was open, and the resistance value after processing was normal, as shown in the figure below:

When the chip was installed, the printing information was displayed for standby after the DDR was installed back, then the fault was eliminated after re-upgrading. Shown as the following figure:

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