Hitachi 51F510, Manual

Page: 82 / 152

DP-4X DIGITAL CONVERGENCE INTERFACE CIRCUIT EXPLANATION
PAGE 06-02
data represents a specific correction signal for that specific location. When the Service Technician makes any
adjustment, the new information must be stored in memory, EEPROM. The EEPROM only stores the 117 differ-
ent 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 and as long as power remains, interpolation no longer has to be made.
This can be seen during an adjustment. If the Interpolation key is pressed on the remote control, what is happen-
ing is that 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 SHOWN IN FIGURE 1:
As can be seen in Figure 1, the Infrared Remote control signals actually manipulate the internal data when the
Service Only Switch is pressed on the Deflection PWB. This process prevents the Microprocessor from respond-
ing to Remote commands, via a Busy line output from the DCU.
INTERNAL CONTROLLER, D/A CONVERTERS SHOWN IN FIGURE 1:
The internal controller, takes the stored data and converts it to a complicated Convergence correction waveform
for each color. The Data is converted through the D/A converter, 1st and 2nd sample and hold, the Low Pass Fil-
ter that smoothes out the parasitic harmonic pulses from the digital circuit and the output Clamp that fixes the DC
offset level.
The DC offset voltage is adjusted by several things.
•
Raster Centering . The Raster Centering adjustment actually moves the DC offset voltage for Horizontal
and Vertical direction. This Offset voltage will move the entire raster Up or Down, Left or Right.
When a complete Digital Convergence procedure has been performed and the adjustment information stored in
memory by pressing the
PIP Mode
button twice (2), it is mandatory to run Sensor Initialization.
If Sensor Initialization is not performed, the set will not allow Magic Focus to operate. If the Magic Focus button
is pressed, the screen will display an adjustment grid instead.
This is done by pressing the
PIP-MODE button on the remote one (1) time, then pressing the SURF button. This
begins a preprogrammed generation of different light patterns. Magic Focus memory memorizes the characteris-
tics of the light pattern produced by the digital convergence module. If a convergence touchup is required in the
future, the customer simply presses the
Magic Focus button on the front panel or activates it from the customer’s
menu and the set begins another preprogrammed production of different light patterns. This automated process
duplicates the same light pattern it memorized from the initialization process, re-aligns the set to the memorized
convergence condition. Note that this process is using “Light” as it’s source. This is a better process than using
waveforms or voltages as it is adjusting using the actual light pattern as see by the customer.
“MAGIC
FOCUS”
SENSORS SHOWN ON FIGURE 1:
This process is a joint effort between the digital convergence module and 8 Photo-sensors, physically located on
the corners and center 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.
Magic Focus is activated by pressing the Magic Focus
button inside the front control panel door or by the Cus-
tomer’s Menu. An on-screen graphic display pattern will be displayed to confirm that the automatic convergence
mode (Magic Focus) has begun.
The digital convergence module produces different patterns for each CRT, and the sensors on the side of the
cabinet pick up the transmitted light and 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 wave-
forms 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 cor-
rected. In most cases, activating the Magic Focus will allow the set to correct itself, without further adjustments.
(Continued on page 3)