Hitachi 51SWX20B Training page 45

DP-2X NTSC VIDEO SIGNAL PATH CIRCUIT EXPLANATION
(See DP-2X Chassis Video Signal Path-NTSC Circuit Diagram for details)
It's important to note that this Chassis horizontal deflection operates at 33.75Khz at all times. Even though this is twice as fast
as NTSC, the set will still display NTSC video with no problem. This is accomplished by the Flex Converter. The Flex Con-
verter will manipulate any input, be it NTSC, Component 480i, 480P, 720P, 1080i to the appropriate Horizontal Frequency
rate of 33.75Khz. This makes this chassis very versatile in it's application.
The following will discuss the signal flow as show in the above listed Circuit Diagram.
TUNER INPUTS:
These sets utilizes two tuners, (DP-26 also has an ATSC Digital Tuner UD2002) one for the Main picture U301 and one for
the PinP (Sub) picture U302. U301 is an intergraded tuner with RF front end, IF decoding, Audio Decoding to Lt/Rt. The
tuner communicates with the Microprocessor via I2C bus. (See Microprocessor Data Communications Circuit Diagram for
details).
The PinP tuner U302 is also an intergraded tuner, however the Audio output is not used.
Both tuners output their respected composite video via pin 18.
•
U301 Main Tuner Output pin 18 to PST1 connector pin 23, to the Selector IC IX01 pin 63.
•
U302 PinP (Sub) Tuner Output pin 18 to PST1 connector pin 19, to the Selector IC IX01 pin 60.
(DP-26 ONLY):
•
UD2002
◊
LUMINANCE: The ATSC (QAM) Tuner (Digital Tuner) Outputs DM Y from pin 7 to the PST1 connector pin
28, to the Selector IC IX01 pin 3.
◊
CHROMINANCE: The ATSC (QAM) Tuner (Digital Tuner) Outputs DM C from pin 5 to the PST1 connector
pin 30, to the Selector IC IX01 pin 5.
These inputs are used while viewing an SDTV or HDTV source, so that there will be an output from the Monitor
Video Jack.
NOTE: The DP-26 has a Digital Tuner (ATSC-8VSB and Cable QAM Tuner). This tuner is UD2002 which also is
the input/output access for IEEE1394. (See the ATSC Block Diagram which is coming up after the Component,
OSD and NTSC Diagram). Even though this explanation is related to NTSC, the ATSC tuner is involved because of
the Video Output on the (Monitor Out) jack. When ATSC or QAM is viewed, the monitor out just have video out-
put. This is accomplished by the ATSC (Digital Tuner) having a Y/C output sent to the NTSC circuit for this pur-
pose.
AUXILIARY INPUT:
This chassis utilizes 5 separate inputs plus a newly added input called DVI. The following will break down those input routes
to the Selector IC IX01.
(1) INPUT 1: This input is only for Component Inputs Y Pr/Pb (31.5Khz to 33.75Khz ATSC) and will not accept Compos-
ite on the Y input. Input one's Y line is input directly into IX02 pin 59 (Y Pr/Pb Selector).
(2) INPUT 2: This input will accept Component Inputs Y Pr/ Pv (31.5Khz to 33.75Khz ATSC) or Y Cr/Cb (15,735Hz.
NTSC). It will also accept Composite Video input as long as there is no Pr plug inserted. Input 2 is routed into the Selec-
tor IC IX01 pin 30.
(3) INPUT 3: This is NTSC composite input only. It also has an accompanying S-Input. Remember that the S-Input takes
priority over composite input, when S-Input is active. Input 3 is routed into the Selector IC IX01 pin 15. The S-Input
inputs are pin 10 for Y (Luminance) and pin 17 for C (Chroma). When an S-Jack is inserted into the plug, an internal
mechanical switch is activated which produces a low to the Selector IC IX01 pin 21 and the Selector IC notifies the Mi-
croprocessor that and S-Jack is installed.
(4) INPUT 4: This is NTSC composite input only. It also has an accompanying S-Input. Remember that the S-Input takes
priority over composite input, when S-Input is active. Input 4 is routed into the Selector IC IX01 pin 8. The S-Input in-
puts are pin 8 for Y (Luminance) and pin 12 for C (Chroma). When an S-Jack is inserted into the plug, an internal me-
chanical switch is activated which produces a low to the Selector IC IX01 pin 14 and the Selector IC notifies the Micro-
processor that and S-Jack is installed.
(5) INPUT 5: On the Front Control Panel. This is NTSC composite input only. It also has an accompanying S-Input. Re-
member that the S-Input takes priority over composite input, when S-Input is active. Video Input 5 is routed through the
PFT connector pin 2 (pin 10 for DP24 only), into the Selector IC IX01 pin 22. The S-Input inputs are routed through the
PFT connector pin 7 (pin 5 for DP24 only) for Y and pin 9 (pin 3 for DP24 only) for C, into the Selector IC IX01 pin 24
for Y (Luminance) and pin 26 for C (Chroma). When an S-Jack is inserted into the plug, an internal mechanical switch is
activated which produces a low through the PFT connector pin 11 (pin 1 for DP24 only), into the Selector IC IX01 pin
28 and the Selector IC notifies the Microprocessor that and S-Jack is installed.
(Continued on page 03-02)
PAGE 03-01