Daewoo DTR-14D3VG, Service Manual

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RGB signal selection has three modes to choose from:
- RGB (composite)
- fast RGB insertion (R1
IN
G1
IN
B1
IN
)
- OSD mode
Before the RGB signal selection the RGB signals are clamped to a similar DC level during burstkey period.
Selection is controlled by the RGB insertion input switch. Fast insertion on the RGB inputs is made active/inactive
via the I
2 C bus(IE1). With the I 2 C bit IN1 the status of the insertion switch input is sensed.
The RGB input stages (i,e,RGB clamps and selection) are linear circuits to handle RGB signals supplied from the
SCART connector.
• Second RGB insertion
The RGB signals inserted via the second RGB-internal YUV-signals are selected. At the YUV-outputs the selected
signal will be available. Converting the RGB signals to YUV signals has the advantage that the YUV-interface and
the YUV processing of the one chip can be used.
(2) RGB-control
• RGB processing
The selected RGB signals (i,e,composite RGB and Rin, Gin, Bin) are via the I 2 C bus controlled on
- contrast
- brightness
- RGB white-point adjust (one individual control per channel)
In OSD mode these RGB signal controls are inactive. OSD is added at the RGB output pins, which then provide
nominal black levels at the RGB-outputs only.
Contrast can be adapted over a 20dB gain range by means of the I2C function : CONTRAST:00 –> 63.
Nominal contrast setting is realised with I
2 C bus setting CONTRAST = 32.
For brightness, a change of DC-level of ± 0.7V at RGB output (w.r.t to nominal) is possible fora change in I 2 C bus
command (BRIGHTNESS:00 –> 63). For nominal brightness, the RGB output is at black level which is equivalent to
a I
CATHODE
of the CRT of 0mA
For white-point adjustment, a ±3dB change in channel gain is possible for a change in I 2 C bus commands (WHITE
POINT RGB:00 –> 63.) Nominal white-point adjustment settings are realised with I 2 C bus setting WHITE POINT
RGB = 32.
RGB output illustration during fast insertion