Video Signal Processing - Philips 7603 series Service Manual

Mono set

Video Signal Processing

The processing circuits listed above are all integrated in the UOC TV processor. The surrounding components are for the
adaptation of the selected application. The I 2 C bus is for defining and controlling the signals.
RF signal processing
The incoming RF signal goes to the tuner (pos. 1000), where the 45.75 MHz IF signal is developed and amplified. The IF
signals then exits the tuner from pin 11 to pass through the SAW filters (pos. 1002). The shaped signal is then applied to the
IF processor part of the UOC (pos. 7200).
Tuner AGC (Automatic Gain Control) will reduce the tuner gain and thus the tuner output voltage when receiving strong RF
signals. Adjust the AGC takeover point via the Service Alignment Mode (SAM). The tuner AGC starts working when the
video-IF input reaches a certain input level. Adjust this level via the I 2 C bus. The tuner AGC signal goes to the tuner (pin 1)
via the open collector output (pin 22) of the UOC.
The IC also generates an Automatic Frequency Control (AFC) signal that goes to the tuning system via the I 2 C bus, to
provide frequency correction when needed. The demodulated composite video signal is available at pin 38 and then buffered
by transistor 7201.