Individual Video Inputs - Sony KDS-50A2000 Training Manual

Individual Video Inputs

The primary objective is to locate the defective component through
viewing the individual video inputs. If the video distortion appears only
in one or two video inputs then the next step is to eliminate the possibility
of a defective or improperly connected external device such as, a VCR or
DVD player. The quickest way to troubleshooting the external devices is
to swap out the suspect device with a known good device at the particular
input.
External Device
Swap Devices and
If the external device or connections are defective then the TV is OK
and the external device needs to be service or the connection to the TV
repaired. If the external devices and their connections are OK then the
next step is to troubleshoot the problem by accessing and displaying each
video input shown in the flowchart.
- Video 1, 3, 4, 5, 8, & NTSC (Missing or Distorted )
- ATSC Tuner & HDMI (Video 6 & 7) (OK)
- Video 1, 3, 4, 5, 8, HDMI & NTSC (OK)
- ATSC Signal (Missing or Distorted )
ATSC & NTSC Signals
Missing or Distrorted
(Only)
HDMI (Video 6 & 7)
Distorted or Missing
(Only)
TVP-23
Individual Inputs
Check
Bad
and
Connections
connections
Good
PC IN (Video 8)
Distorted or Missing
(Only)
Video 2
Missing or Distorted
(Only)
The rationale behind this troubleshooting method is that each of these
video input takes an altogether or somewhat different path through the
video processing system. This fact enables you to determine the defect,
in some cases, down to the component level, and in almost all cases,
down to at least the board level. For example, if the distortion appears
in Video 1, 2, 3, 4, 5, 8, and NTSC Tuner, however, it does not appear in
the ATSC Tuner and HDMI then the defect exists in the A1-Board. The
reason for this conclusion is due to the fact the signals from Video 1,
2, 3, 4, 5, 8, and NTSC Tuner must travel completely through the A1-
Board, and the ATSC Tuner HDMI are applied directly to the B1-Board
completely bypassing the A1-Board. The fact that the ATSC Tuner and
HDMI are not distorted indicates that the QM-Board and CCPX on the
B1-Board respectively are functioning properly and the defect must be in
the A1-Board.
The opposite of the previous conclusion is true if the video distortion
appears in the ATSC Tuner input but not in the Video 1, 2, 3, 4, 5, 8, HDMI
and NTSC Tuner. In this case, the defect would most likely exist in the
QM-Board. The reason for this conclusion relies on the fact that Video
1, 2, 3, 4, 5, 8, HDMI and NTSC Tuner signals travel completely through
the A1-Board and B1-Board and there is no distortion. This provides a
strong indication that the A1-Board and B1-Board circuitry is functioning
properly. The fact that the ASTC Tuner signal path is solely through the
QM-Board and the signal is distorted provides strong evidence that the
defect exists in the QM-Board.
Note that the QT-Board is not suspect in the case because the NTSC
signal is not distorted and it is demodulated along with the ATSC signal
on the QT-Board. Therefore, the QT-Board is most likely functioning
properly.
The same deductive reasoning can be applied when troubleshooting video
defects using the other video inputs shown on the flowchart. This method
simple involves knowing the path the input signal must take through the
video processing system to reach the display. With this knowledge you
can effectively divide the video system into distinct areas, and therefore,
isolate the defect.
6. Video Processing System
72