The
2004 DLP televisions are separated into two categories, one being the HM84 HD
monitor series and the HM94 HD Integrated series. This will cover the basic
design and troubleshooting of the audio and video section of the HM84 HD
monitor series. This module is divided into three major areas. We will first
discuss the specifications of the input signals and display. Then we will move
into the overview and block diagrams of the Audio & Video signal flow. The
last portion of this the module will cover troubleshooting the audio and video
NTSC Tuner
Receives the NTSC signal format (525
lines interlaced scanning) for consumer televisions in the United States. A
typical NTSC tuner receives VHF channels 2 to 13, UHF channels 14 to 83, and
Cable TV channels mid band A8 to A1 and A to I, super band J to W, hyper band
AA to ZZ - AAA and BBB, and ultra band 65 to 94 and 100 to 125.
Composite Video
Refers
to a video signal where both the luminance component and the color component(s)
are transmitted on a single wire or broadcast in a limited bandwidth. The
luminance and color information must be separated before the picture can be
displayed.
S-Video (also called Y/C)
A video signal transmitted as two
sub signals requiring two separate wires: luminance (technically referred to as
Y) and color (C). Luminance is composed of black and white video signal and the
sync signal. Chrominance is the color (modulated on a carrier) video signals.
Component Video
Video and Audio Signal flow
Note that the Rear A/V jack
panel is a hub for most signal inputs, processing and switching. Knowing this,
can trace signals to and from the Rear A/V jack panel to its input or output
circuits. Additionally, when a problem with an input, output, or the Rear A/V
jack panel itself is discovered, the power distribution can be investigated for
possible supply problems. Then if no supply problems are discovered, the board
at a fault can be repaired.
This unit is, in some circuit areas, only serviceable
to modular level. However it is sometimes an advantage to service non-difficult
obvious trouble to component level and repair the problem rather than replace
the entire circuit board. This becomes an important aspect if the unit is out
of warranty. An interconnect diagram of the signal paths in this unit. Listed
on this block are plug numbers, as they are listed on the board, and in the
schematics, for both ends of the path.
Rear AV Board connections and components.
All input sources are routed
through the Rear A/V board. This is important to mention because in past PJTV
models, the A/V switching IC, QV01, was located on the signal board. As shown
in Figure 3, QV01 is located just above the jack panels. Sub-picture processing
is done here as well by IC QY501 and QY100. QS01 located toward the lower right
hand side, switches the audio selection for the inputs. One interesting area
includes service ports used to access data and service protocols.
Voltage requirements consist of a 9V source and two
5V sources. These voltages are supplied via connector BB70 through the
IMA/tuner board. This should be noted since the Rear A/V is not directly
connected with the power supply board. Looking at the left side of Figure 4,
the input sources are shown with the corresponding connection, if applicable to
that particular input source. Composite
and S-video sources are labeled E1, E2 and E3. Figure 4 illustrates the signal
path through QV01. Sub picture composite video output at pin 51 is routed to
QY100 for comb filtering. Sub picture (PIP or POP) Y/C and Y, Cb, Cr is routed
directly to QY501 for signal processing of the sub picture. The output
from QY501 is a Y, Cb, Cr signal. Both the main and
sub picture signals are routed through connector PV04 to the
DBEP/Signal/G-Hyper Board.
At the lower right, note the service port connections
and plugs are not related to nor directly connected to any video or audio
signal paths. This allows direct connection to the data chips located on the
DBEP/Signal/G-Hyper Board.
Contd:
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