Zenith R50V26 Service Manual page 34

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HD FOCUS SENSORS AND INTERFACE
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MICROPROCESSOR
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RAINFOREST IC (Video Processor).
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SERVICE ONLY SWITCH
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MAGIC FOCUS (HD Focus) activation control.
THE DIGITAL CONVERGENCE UNIT (DCU)
The DCU is the heart of the Digital convergence circuit.
Held within are all the necessary components for gener-
ating the necessary waveforms for correction, and asso-
ciated memories for the adjustment data and Magic Focus
Data.
The Block above shows the relationship of the DCU to
the rest of the set. Note that the light being produced
by the CRTs is what is used by the sensors for Magic
Focus. This allows the DCU to make adjustments regard-
less of circuit changes, by actually using the light on
the screen to make judgments.
EEPROM AND SRAM
Each color can be adjusted in any one of 117 different
locations. The internal workings of the DCU can actu-
ally make 256 adjustment points per color. These ad-
justment points are actual digital data stored in memory.
This data represents a specific correction signal for that
specific location. When the Service Technician makes
any adjustment, the new information must be stored in
the, EEPROM. The EEPROM only stores the 117 different
adjustment points data, the SRAM interpolates to come
up the additional 139 adjustment points for a total of
256 per color. The EEPROM data is slow in relationship
to the actual deflection raster change. The SRAM is a
very fast memory. So, during the first application of AC
power, the EEPROM data is read and the SRAM makes the
interpolation. As long as power remains, interpolation
no longer has to be made.
This can be seen during an adjustment. If the Interpo-
lation key is pressed on the remote control, the SRAM
must make those additional calculations beyond the 117
made by the Servicer and this is all placed into memory.
INFRARED REMOTE CONTROL INPUT
The Infrared Remote control signals manipulate the in-
ternal data when the Service Only Switch is pressed on
the Deflection PWB. This process prevents the Micro-
processor from responding to Remote commands, via a
Busy line output from the DCU.
INTERNAL CONTROLLER, D/A CONVERTERS
The internal controller, takes the stored data and con-
verts it to a complex Convergence correction waveform
for each color. The Data is converted through the D/A
converter, 1st and 2nd sample and hold, the Low Pass
Filter that smooths out the parasitic harmonic pulses
from the digital circuit and the output Clamp that fixes
the DC offset level.
PV154 - 923-03506
CIRCUIT DESCRIPTIONS
The DC offset voltage is adjusted by several things.
When a complete Digital Convergence procedure has been
performed and the adjustment information stored in
memory by pressing the MULTI button twice, it is
necessary to run Sensor Initialization. This is done by
pressing the MULTI button on the remote once, then
pressing the PinP Ch button. This begins a
preprogrammed production of different light patterns.
HD Focus memorizes the characteristics of the light
pattern produced by the digital convergence module.
If a convergence touchup is required in the future, the
customer simply activates HD Focus via the Customer's
Menu and the set begins another preprogrammed
production of different light patterns. This automated
process that duplicates the same light pattern it
memorized from the initialization process, re-aligns the
set to the memorized convergence condition.
"HD FOCUS" SENSORS
This process is a joint effort between the digital
convergence module and 4 Photo-sensors, physically
located on the middle edges of the cabinet, just behind
the screen. The physical placement of the sensors assures
that they will not produce a shadow on the screen that
can be seen by the customer.
HD Focus is activated when the customer selects HD
Focus in the Customer's Menu. An on-screen graphic
will be displayed to confirm that the automatic conver-
gence mode (HD Focus) has begun.
The digital convergence module produces different
patterns for each CRT, and the sensors pick up the
transmitted light, generate a DC voltage. This voltage
is sent to the DCU and converted to digital data and
compared with the memorized sensor initialization data.
Distinct patterns will be generated in each primary color.
As the process continues, the digital module
manipulates the convergence correction waveforms that
it is producing to force the convergence back into the
original memorized configuration.
When all cycles have been completed, the set will return
to the original signal and the convergence will be
corrected. In most cases, activating HD Focus will allow
the set to correct itself, without further adjustments.
EXPLANATION OF THE DIGITAL CONVERGENCE INTER-
CONNECT DIAGRAM:
INFRARED RECEIVER:
During normal operation, the IR receiver directs it sig-
nal to the Main Microprocessor where it interprets the
incoming signal and performs a predefined set of op-
erations. However, when the Service Only Switch is
pressed, the Main Microprocessor must ignore remote
control commands. Now the DCU receives these com-
mands and interprets them accordingly. The Micropro-
cessor is notified when the DCU begins its operation by
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ZP26/28 - SERVICING