EMERSON LCD TV 26-32 Service Manual

Service manual

for 2652 -3252

Block diagram

LM21 chassis was combined with PHILIPS 3rd ‘One Chip’ technology named UOCIII chip set. The chip is integrated by a 51 Core

MPU as control center, and 128Kbyte or 256Kbyte code Flash-ROM. The PHILIPS VSP (Video signal processor) is used as TV’s

picture processor and SSD (Sound signal DSP) used as TV’s audio signal processor. The IF signal is output from tuner and

amplified by Pre. Amplify department. After the signal through the picture SAW and sound SAW Filter(quasi separate) then it was

input the UOCIII chip. Inside the chip the signal was demodulate YC separate and RGB decode by VSP; the DSP of SSD

department was worked for FM-demodulate, NICAM or A2 stereo decode, all kinds of audio effect processes include BASS, Treble,

Volume and 5 section equalizer etc. the video output of UOCIII is RGB, H_sync, V_sync; audio output is L, R channel audio signal.

The RGB,H,V_sync and Y PbPr input were selected by a video switch named FSAV330, through the video switch they were into

MST6151A, the scale chip. Inside the chip A/D depart change video signal into digital signal at first. Second the 3D de-interlace

part process the digital video. After the movement correction, color progress etc. finally the scaling engine scale the picture into

1366 x 768 and output in LVDS format to the LCD panel. MST6151A was also have a VGA port and DVI port for different high

quality signal input. But all analog video (eg. AV; S-video; SCART) was input into UOCIII chip at first, than the signals were into

MST6151A after they were changed into RGB signal. At the same time the audio signal was processed by SSD part inside the

UOCIII then the audio will be amplified by TPA3008 (TI’s class-D power amplifier) before they were input into louder speaker.

UOCIII chip was also with a headphone audio output, the headphone signal were amplified by LM358 (NS’ double operate amplify).

All parts of system were controlled by 51_core MCU inside UOCIII through I2C bus except scale chip. The scaler MST6151A was

controlled though 4 Bit parallel bus.

Signal Flowing Chart (analog part)

The analog video part and audio part chips of system were assembled in one main board with tuner. The RF signal passed the tuner

was changed frequency in IF signal, before it was transferred in Prep. Amplify. The Pre Amplify was made up with Q703, it was

used to compensate the IF losing through the SAW filter. The 33V tuning voltage was outputted by Q504, L511, C530. They were

buildup an oscillator to produce 5V AC current approximately 500kHz. Then AC current was rectified by voltage multiplier(D504

double diode). The voltage is changed with the tuner’s demodulation in different channels. The Prep. Amp. Amplified IF signal

before it pass through the SAW filters(K3953,K9650). IF signal were inputted into UOCIII chip after passed the quasi separate

architecture SAW filters. K9650’s pass band could be switched for compatible DK.BG,I and L/L’. so Q701 and D701 were

combined band switch circuit to change K9650’s pass band. When IF was inputted into UOCIII, the VSP part demodulate the video

signal, the comb filter separate Y/C signal, the color matrix compose RGB signal. Finally RGB signal and negative pole were

transmitted to socket CN805, the cable lines transmit the signal into the digital PCB. At the same time of video demodulation the

TeleTXT signal was also decoded by VSP part and the TXT was over lap RGB signal in OSD format. The audio signal was

demodulated by DSP inside SSD part(include Germen’s A2 format and British’s NICAM format decode). The back part of SSD

worked as sound processor. It’s include volume, bass, treble adjust; 5 sections equalizer and BBE effect. At last L/R channel sound

was outputted form UOCIII chip’s Pin-60, Pin-61 to TPA3008’s input ports. After been power amplified audio signal was

transmitted to loudspeaker.

Functions for each module:

1) Tuner, Pre. Amplify and SAW filters:

The tuner with frequency synthesizer was PAL/SCAM compatible and controlled by I2C bus. Tuner’s Pin-1 is AGC control Pin, The

AGC voltage was outputted by UOCIII’s Pin-98(AGC_out), the range of AGC is 0V~4V which have 64 ranks adjusting in factory

menu. The Pin-2 is NC(not connect). The tuner’s slave address was selected by Pin-3, it was connected to GND, so the tuner’s slave

address is 0xC0. Pin-4(SCL)and Pin-5(SDA) were I2C control bus. They were connected to I2C BUS through 2 100Ω

resistors(R702,R704). Pin-6 is NC. Pin-7 is tuner’s 5V supply pin. Pin-8 is NC. Pin-9 is 33V tuning voltage supply pin, the voltage

of the pin will changed from 6V~20V when tuner adjust at different channel. Pin-10 is NC. Pin-11 is IF output pin. The R707 and

C703 were matched input impedance of Pre. Amplify. Been the Pre. Amplify, Q703’s gain was select by the ratio of R706 : R711. In

system the Pre. Amplify’s gain was 7 times.

The tuner’s Pin define were list in the form as follows:

After been Pre. Amplified, the IF signal will pass the SAW filter. The picture SAW is K3953(EPCOS part number), K3953’s pass

band is 33.9MHz~38.9MHz, it’s baud chart is listed as follows:

Pin No. Terminal name Define and Description Voltage

1 AGC （AGC voltage supply） 4.0V Gain Max.

2 —— —— ——

3 AS （Slave Address Selection Line） -0.3V To 5.5V

4 SCL SCL（Serial Clock Line） -0.3V To 5.5V

5 SDA SDL（Serial Data Line） -0.3V To 5.5V

6 NC NC（No Connected） ——

7 BP （+B For PLL & Mixer） +5V

8 —— —— ——

9 BT/LOCK （Tuning Voltage Supply） 33.0V

10 —— —— ——

11 IF1 （IF Output） ——

The audio’s SAW filter is K9650(EPCOS part number). It could be switched at 2 pass band. Channel 1 is for 40.40MHz audio carry

frequency of L’-NICAM stereo audio signal. The baud chart is as follows: