Philips TC5.1L, Service Manual

Circuit Descriptions, Abbreviation List, and IC Data Sheets

EN 19

TC5.1L CB

9.

9.1.3

Tuning Section

This section mainly consists of the tuner (TU101), the IF pre-
amplifier circuit and the SAWFILTER. 

Table 9-1 Tuning section 1

Table 9-2 Short specification of the tuner

From Pin58 of IC101 the I2C bus clock signal goes to the tuner. 
The tuner works during the clock time. IC101 will send out a 
data signal from Pin57 to control the tuner's working state by 
controlling the +33V voltage. +33V is provided from Pin10 of 
T803. That voltage is put into the tuner at Pin7. A circuit inside 
the tuner tran33V into a voltage between 0 and +33V 
(as a function of the data, sent by IC101). 
The AGC signal is a close loop control voltage that keeps the 
amplitude of the signal constant.
Output of tuner is the Intermediate Frequency signal (IF signal). 
The IF signal will pass pre-amplifier circuit (refer to the picture 
below). The amplified IF signal passes the SAW filter and is 
then sent to IC101 Pin41/42.
IC101 creates a CVBS signal and sends it out from Pin30. 
CVBS will be selected by IC901, and then pass from Pin13 of 
IC901 to Pin20/24 if IC101. IC101 will demodulate the CVBS 
signal into an R, G, B signal. Next IC101 will send this R, G, B 
signal from Pin50/51/52 to the CRT board.

Figure 9-3 Pre-amplifier circuit

9.1.4

Sound Process Section

The SIF signal is sent out together with the TV signal from 
Pin30 of IC101. It passes through Q203, R225. X202 and a 
High-pass filter (consisting of C254, L206, C253) filters out the 
video signal and low frequency interference. 

Figure 9-4 Sound process section 1

SIF will be finally sent into Pin2 of IC1001. An analog automatic 
gain control circuit (AGC) allows a wide range of input levels. 
The analog-to-digital conversion of the IF sound signal is done 
by an A/D-converter. The high pass filter, formed by a coupling 
capacitor at  suppresses video components.
IC1001 is controlled via the I2C bus slave interface. 
The AV sound signal will be directly sent to Pin37/38 or Pin40/
41 of IC1001. Q901/2 and Q903/4 form Emitter-Follower 
circuits to provide a better load ability.
The (analog) sound signal will go from Pin26/27 of IC1001 to 
Pin4/12 of IC602. IC602 is a dual bridge amplifier. The output 
voltage of IC602 drives the speakers. The volume is adjusted 
via the I2C bus.

Figure 9-5 Sound process section 2

Pin

Symbol

Description

1

AGC

Auto gain control

2

AS

I2C bus address select 

3

SCL

I2C bus serial clock

4

SDA

I2C bus serial data

5

6

BP

Supply voltage tuner s5V

7

BT

Supply voltage tuning s31V

8

IF

Intermediate frequency out

Receiving
Channel

VHF LOW BAND: CH2~B(55.25~127.25MHz)
VHF HIGH BAND: CH C~CH W+11(133.25~361.25MHz)
CH W+12~69(367.25~801.25MHz)

Receiving
System

NTSC

Intermediate
Frequency

Picture carrier: 47.74MHz
Colour carrier: 42.17MHz
Sound carrier: 41.25MHz

Antenna Input
Impedance

Unbalanced 75Ohms

Output Imped-
ance

Unbalanced 75Ohms

Band change-
over system

Digital change by PLL IC

G_16340_023.eps

100306

G_16340_024.eps

100306

G_16340_025.eps

100306