Grundig 40VLE630BH, Service Manual

Page: 70 / 180

TP CHASSIS / TELEVISION
70 September 2011
TP chassis utilizes hybrid tuner. Receiving both analog and digital broadcasts from
the cable, the tuner obtains analog and digital IF (inter frequency signals) of the
broadcasts. This ALPS brand tuner uses 5V power as antenna supply for active
antennas. This selection can be made from user menu and controlled by 5V_TA
signal from the chassis (Leg 1). When the signal of analog broadcast is low
depending on the RFAGC signal coming from main IC, signal levels are strengthened
by the coefficient of amplification that is calculated by main IC (Leg 2). Tuner is
locked to the desired channel by communicating with main board and main IC,
depending on the selected source, through I2CT2_SCL and I2CT2_SDA lines. It
selects the desired frequency by filtering other frequencies and transforms the signal
as to enter main IC. This chassis does not have a separate demodulator IC.
Demodulation is performed in main IC. Here, I2C protocol is used for the purpose of
communication (Leg 7 and 8). Leg 6 sends 4MHz signal of 33V as reference. We
leave this leg empty. Tuner's own power supply is 5V (Leg 3).
Leg 9 gives analog IF output while Leg 11 and Leg 12 give digital IF output. Leg 10
sends IF AGC value used in digital broadcasting, from the digital demodulator.