Signal Flow - Philips B8 Series Service Manual

SIGNAL FLOW

The incoming TV RF signal is applied to the U/V Tuner via the Antenna RF Input. The IF signal is
developed within the U/V Tuner, then amplified by an IF Preamplifier located inside the Tuner.
The amplified IF signal is sent from Pin 11 of the U/V Tuner to the SAW Filter, Y200. The SAW
Filter produces bandpass shaping for the IF signal before it is applied to the TV Signal Processor
Integrated Circuit, IC271, for processing. AGC (to the Tuner) and AFT (to the Microcomputer)
signals are developed within IC271 and then sent to the Tuning System for RF Amp gain control.
Sound IF signal processing for the B8 Chassis is performed by coupling the 4.5MHz Sound IF
signal from IC271, Pin 6, via a Buffer Amplifier, Q221, and 4.5MHz Band Pass Filter, Y220, into
IC271, Pin 1. Audio is output from Pin 15 in mono versions and applied to the Audio Amp Output
IC, IC730, to drive the speakers. For the stereo equipped sets, the detected baseband audio
signal exits IC271, Pin 15, and then enters the Stereo Decoder IC200. The Stereo Decoder has
Internal/External switching, via the control input on Pin 21, to allow either the detected baseband
audio or External Audio from another source to be routed through and exit to IC730 and IC740.
Composite video from IC271, Pin 6, is buffered by Q221 and then passed through a 4.5MHz
Trap, Y221, to remove any sound products present. This signal is buffered again by Q225 before
it goes back to IC271, Pin 13. Depending on the part number of IC271, either BS315 or BS316
will be installed. With BS315 installed, The CC Video comes from Q225. If BS316 is installed,
the CC Video comes from Pin 38 of IC271. Internal/External switching of the video is done within
IC271. The chroma and luminance signals are then processed by the Chroma/Luminance
Process block within IC271. Sync input from the Chroma/Luminance block to the