Service manual

CA-7
Microprocessor Control
types of on-screen display (OSD). Neither sync pulses come directly from the video processor where they
are first produced. Horizontal sync is actually fed back from the sweep transformer on the flyback pulse
line. Vertical ramp signals feed the base of Q6002. Sync is produced on the collector and fed to the
vertical amplifier and through R6006M to the V-Sync pin of the micro. OSD or CC (closed captions) are
sent as processed RGB (red, green, & blue) from pins 50, 51, and 52. At those times it is necessary to
blank out main video, a fast-blank (FB) pulse is sent to the video processor from pin 49 along with the
processed RGB. An exception to this occurs when PiP is displayed. Under that circumstance, the fast-
blanking pulse without RGB is sent to the video processor.
Some CA chassis feature a halftone function that dims video surrounding OSD. This halftone circuit is
described in the video section, but is controlled by a DC level from pin 40.
Closed captioning display is accomplished in the microprocessor by use of the composite video into pin 22.
Here a data slicer extracts the caption information and outputs it to the RGB pins when captioning is re-
quested by the user. Note that when OSD needs to be on the screen, such as after a channel change or
during a volume change, the OSD will have priority, and CC will mute. IC6000 also gains synchrony
information from the composite video stream.
Pin 6 is a signal detection pin. When the tuner sends a bona-fide signal to the video processor, it separates
the horizontal sync signal from the IF and sends it to this portion of the microprocessor. It can then be used
to determine if a certain channel is carrying an active broadcast.
Automatic frequency correction (AFC) is sent to the microprocessor via pin 3. The DC level on pin 3 tells
the microprocessor if it needs to communicate an adjustment to the tuner to allow for clearer channel
reception. The ideal voltage level here should be approximately +2.5 volts.
IC6000 provides CRT-protection for the set through pin 13. Operation of this shutdown depends on a DC
level from the CRT protection circuit off the vertical amplifier circuit. Should the vertical IC2100 fail, the
DC level will no longer be present. In this situation, the CRT-protection latch will shut the receiver down
three seconds after detecting the failure. This circuit will prevent the CRT from burning a horizontal phos-
phor line in the center of the screen or, worse yet, cutting the yoke end of the tube off completely.
The remainder of the input and output pins of IC6000 are adequately described in other sections of this
manual. Refer to the video, audio, and deflection sections of the CA chassis for these descriptions.
IC Location Part # Notes
IC6000 221-01384-01
221-01384-02 Refer to Service Manual
221-01386-01 for Corresponding Model
221-01387-01
IC6001 221-00745-04 All Models
IC6002 221-01177A All Models
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