Panasonic EURO 4 Chassis, Technical Manual

Page: 117 / 163

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34
Chapter 3 EURO 4H Supplement
2.9. CRT Measurement and Control
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The DDP is also equipped with an A/D converter
which is used to perform Tube and Picture
measurement, this information being fed from the
Y-Board
via 3 transistors. These transistors
depending upon the Y-Board being used.
For the Y-Board TNP8EY017 please refer to the
EURO 4 Technical Guide (TZS8EL001).
The information fed from the Y-Board (TNP8EY018)
is fed via transistors Q351, Q361 and Q371 to the
sense input pin 17 of the DDP IC1504. The reference
voltage for the measurement A/D converter being
input via pin 29 also of the DDP IC1504.
2.9.1. Tube Measurement
Tube measurement is carried out during vertical
flyback, during this period two sets of measurements
are gated back to the DDP IC1504 pin 17.
The two sets of measurements taken during tube
measurement being cut-off for the RGB systems and
white drive for either of the R, G or B which are carried
out sequentially.
The input range of the A/D converter is set between
0 - 1.5V which has to be switched to ensure that its
input range is not exceeded. The input range of the
A/D converter is dependant upon the measurement
being taken and is controlled by pins 15 and 16 of the
DDP IC1504.
During cut-off measurement the input range of the
measuring A/D converter is set by resistor R603
(located on the E-Board). However as the white drive
measurement contains alarger current range, resistor
R1538 is also switched into the measurement A/D
converter input along with R603 thus keeping the
measured value in the range of the A/D converter.
This information then passes via the I
2
C bus to the
microprocessor IC1101 which evaluates this data and
compares the data set in the memory (during
alignment adjustment) to continuously match the
measured data.
These correction values again pass via the I
2
C bus to
the fast processor in the DDP IC1504. Here the RGB
output stages are corrected according to the values
supplied, thus compensating for CRT and component
aging.
2.9.2. Picture Measurement
To ensure that the Picture Measurement is kept within
the range of the A/D converter resistor R603 is used
along with R1539.
This Picture Measurement which is fedback to the
DDP IC1504 pin 17 sense input is used to perform
Beam Current safety (discussed on page 30 of the
Euro 4 Technical Guide under the heading ABL
protection) which is software controlled.