Cpu; Deflection And Geometry Control; Sharpness Control; Exposure Control - Polaroid 8035 Repair Manual

8K Series ProPalette Repair Manual

CPU

ProPalette's CPU is a V53 (Intel 186 compatible) with a TI DSP. It also has 4 megabytes
of DRAM (expandable to 14 megabytes at the factory), and a field-upgradeable 512
kilobyte flash firmware memory.

Deflection and Geometry Control

Pixel deflection is controlled digitally via a 2D lookup table, 16-bit DAC, sample and
hold and a low-pass filter. Instead of magnets on the CRT yoke, the 8K Series ProPalette
models correct geometry (pincushion) digitally through the 2D, 16-bit lookup table
customized at the factory for each unit and stored in flash memory.

Sharpness Control

The ProPalette provides dynamic focus through a 2D lookup table and a 12-bit DAC. The
lookup table is customized for each unit at the factory and stored in flash memory. The
system also reduces pixel degradation in the corners by correcting for spot astigmatism
with internal neck magnets.

Exposure Control

ProPalette controls exposure as follows:
Exposure Parameter
Pixel brightness
Compensation for CRT
brightness drift (Autoluma)
Compensation for CRT
phosphor color balance drift
4
COS (compensation for
brightness fall-off at corners)
Control Method
Intensity-modulated 1D lookup table and 16-bit
DAC
12-bit ADC with 8-bit gain control, providing more
than 20 bits of dynamic range. Brightness is
checked before each exposure and corrected when
necessary.
Periodically recalibrated via photocell viewing CRT
through the filters.
2D lookup table and 12-bit DAC.
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Theory of Operation