B245/B276/B277/B268/B269 Service Manual 18-Jan-06
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SBU (Sensor Board Unit)
The CCD converts the light reflected from the original into an analog signal. The CCD line
has 7,400 pixels and the resolution is 600 dpi (23.6 lines/mm).
The CCD has two output lines, for odd and even pixels, to the analog processing circuit. The
analog processing circuit performs the following operations on the signals from the CCD:
1. Z/C (Zero Clamp):
Adjusts the black level reference for even pixels to match the odd pixels.
2. Signal Amplification:
The analog signal is amplified by operational amplifiers.
After the above processing, the analog signals are converted to 8-bit signals by the A/D
converter. Each pixel will be assigned a value on a scale of 256 grades. Then, the digitized
image data goes to the BICU board.
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