Video Path Troubleshooting - Sony KDP-57XBR2 Training Manual

Chapter 20 - RA-5A Video Path Troubleshooting
Overview
The RA-5A chassis incorporates a DTV tuner and decoder circuits in a shielded board known as the "Q Box".
MPEG2 decoding of ATSC broadcast signals along with Digital Dolby® decoding circuitry allows for reception of
all current formats. The DRC
to display the customer menu along with certain HD setup information. An overall view of the video paths can be
seen in Figure 20-1. An important point to remember is that all video signals pass through the Q Box before
being sent to the video process IC3008. The Q Box is not serviceable and must be replaced as a unit.
The B board contains the necessary switching and processing circuitry for both analog tuners and all of the
external input lines. The Q Box is mounted to this board. The main microprocessor IC001 is also located on the
B board and supplies service data OSD to the video processor.
The A board contains the video process IC3006 for final distribution to the red, green and blue CRTs. The AD
board is mounted to the A board and contains the digital convergence circuitry, along with a RGB output to
IC3006 to display convergence data, auto-registration flags for the sensors during Flash Focus
crosshatch and dot patterns.
Although this chassis is currently a board level repair unit, the distribution of the video signals among three main
boards requires diagnostic procedures to determine which board to replace. If the boards become unavailable
in the future and component level troubleshooting becomes necessary, the diagnostic methods covered in this
chapter will become more valuable.
Video failures fall into three main categories:
1. No video
2. Distorted video
3. Improper level
Although the video signals are routed through many different paths depending on the type of signal being received,
these different pathways can be used to an advantage when diagnosing video failures. The picture & picture
(Twin Picture) feature provided by the MID
two video signals simultaneously, isolating which stage is causing the problem can be accomplished easily. This
feature will be used extensively in the troubleshooting procedures to follow.
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and MID process circuits are located on this board along with an OSD generator
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circuitry provides a useful diagnostic tool. Since it is able to display
20. RA-5A Video Path Troubleshooting
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, and internal