Color Restoration; Color Restoration Circuit (Red Only); Color Restoration Function (Red Only) - Sony CPD-420GS Training Manual

Color Restoration

OVERVIEW
The Color Restoration function can be performed by the user to restore
the White Balance of the CRT. The CRT beam current is measured when
White Balance is performed via the DAS/CATS software. The CRT beam
current is converted to a voltage and stored in registers. During the Color
Restoration function, these registers are sampled and the CRT beam
current is adjusted until they equal the values stored in the registers. The
Color restoration function can only be accessed via the OSD menu and
activated after an initial warm up period of approximately 30 minutes.

Color Restoration Circuit (Red only)

T
he Color Restoration circuit is comprised of the Micro IC1001 (N Board),
IC001 (RGB DRIVE), IC003 (OSD), IC004 (CUTOFF AMP), CRT and the
current sensing components. Each of the Red, Green and Blue cathode
beam current sensing circuits are identical and only the Red cathode beam
current circuit will be explained.
As the video image changes, the Red cathode beam current also changes.
This current change flows through R116, R122 and R108 to CUTOFF
AMP IC004/6 (R.B.C.F.). The P-P video level is AC coupled by C121, DC
clamped by D120 and rectified by D108. This voltage level is input to
IC003/22 (RCI) where it is A/D converted by IC003.
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This digital value of the Red cathode beam current is stored in an indi-
vidual register. During the White Balance adjustment via the DAS/CATS
software, the average DC level is sensed and stored in the registers.

Color Restoration Function (Red only)

The Color Restoration function is activated via the OSD menu only after
an initial warm up period of approximately 30 minutes. When the Color
Restoration function is activated, the Micro IC1001 (N Board) via the I
bus instructs IC003 (OSD) to output an all white pattern to be displayed
on the screen. IC003/22 (RCI) samples the Red beam current input and
compares this DC level to the level stored in the register. If the levels are
not the same, IC003 outputs correction data via the I
(N Board). IC1001 (N Board) via the I
the DC level output at pin 3 (R BKG) and the P-P level output at pin 20 (R
OUT). The DC and P-P levels are varied until the measured beam cur-
rent is equal with the level stored in IC003 register. Once the Color Res-
toration function is completed, the input video signal is displayed.
2 C data bus to IC1001
2 C data bus instructs IC001 to vary
2 C