Bc Board - Sony VPL-PX20 Service Manual

3-3. BC Board

The BC board controls the contrast, bias, W/B, etc. of the linear digital signals from the BBC board, then
performs gamma correction by LUT (Look Up Table) and 3D gamma correction which corrects in planes
according to the gradation, converts the signals from digital to analog before outputting them.
1. IC502 (CXD9512Q)
IC502 (CXD9512Q) has a 48 bit 2-pixel series input and 30 bit (10bit/pixel) straight output.
Therefore a 2 clock whose phase matches the input clock is required.
2. IC501
IC501 is an IC generating 2 clock corresponding to the frequency diffusion. It outputs the same clock
as the input to CLKB and the 2 clock to CLKA according to the phase of the input clock.
IC 500 (Pin 1 of IC501) is incorporated to match the timings of the data and clock.
3. IC503
IC503 is a 64 Kbits (8 Kbytes) EEPROM memorizing LUT (Look Up Table) and the 3D gamma
data. It exchanges data with IC502 using I
4. IC511
IC511 generates RESET signals for IC503.
5. IC505
IC505 is a switching buffer for OSD display of PW264 when outputting the internal signals of IC502
in gamma adjustments, etc.
When PW OSD ENA is LOW, DG07 and DGE7 are sent to ODD_YS and EVEN_ YS respectively
to control the ON/OFF of the OSD. DR07 and DRE7 are also sent to ODD_YM and EVEN_YM
respectively to control the OSD half tone.
When PW OSD ENA is HIGH, both YM and YS are pulled-down to the LOW level by the
resistance, and the OSD of this route goes off.
6. IC506
IC506 is a 10-bit D/A converter. It converts gamma corrected digital data to analog signals.
The output when the full-scale (3FFHEX) is input becomes approximately 0.75 Vp-p after
termination at 75 Z of the C board.
7. D500
D500 is an external reference voltage source to improve accuracy. It generates 1.25± 2% voltage.
To avoid the effects of the digital circuit and input signal, IC506, D500 receives the supply of analog
5V from the C board.
Other circuits operate on digital 3.3V from the BB board.
8. S500
S500 switches the I 2 C signal, writes the LUT data using the I
connected to CN503 so that the operations of IC502 (CXD9512) can be controlled directly.
During normal operations, IC502 is connected to the I
the main microprocessor.
2
The slave address of I C of IC502 is 76 Hex.
3-4
2 C signals (slave address is A2).
2 C signal from the external tool
2 C line from the Y board and is controlled from
VPL-PX20/PX30