Signal Flow - Philips 13PT30L1 Service Manual

SIGNAL FLOW

The incoming TV RF signal is applied to the U/V Tuner via the Antenna and RF input. The 45.75MHz 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 Pins 10 and 11 of the U/V Tuner to the SAW filter, 1003. The SAW filter
produces bandpass shaping for the IF signal before it is applied to the TV Signal Processing Integrated
Circuit, 7250 for processing. AFT voltage is developed within 7250. These voltage values are then sent to
the microcomputer via the I 2 C bus for Tuner Oscillator frequency correction.
Sound IF signal processing for the E8 chassis is performed by coupling the 4.5MHz Sound IF signal from
7250 Pin 6 through transistor 7266 and a 4.5MHz band pass filter 1001 to Pin 1 of 7250. In the Mono
version, Baseband Audio from Pin 15 of 7250 is buffered by transistor 7951 before being applied to Bass
and Treble circuits. The outputs of the Base and Treble circuits are applied to a 1 watt amplifier 7954 in the
US version or a 2 or 3 watt amplifier 7953 in the Latin version. In sets equipped with a Stereo module,
Baseband Audio from Pin 15 of 7250 is fed to the Stereo Decoder module. The DBX Stereo Decoder
module has internal/external switching, AVL switching, volume control, and alignment settings via the I 2 C
bus (SDA & SCL). Internal/external switching, AVL switching, and volume control for the Normal Stereo
module are performed through individual control lines from the Microcomputer. Audio output amplifiers for
both the DBX and Normal Stereo versions are located on the Stereo module. AVL switching for the Mono
version is performed in 7250 via the I 2 C bus. Volume for the Mono set is controlled in the Audio Output