Akai PT-11, TV-2111TGB, TV-1411TGB Service Manual

SERVICE MANUAL

PT-11 CHASSIS

AKAI

TV4411TGB

Modification reserved

Ti/-2111TGB

PT-11 Chassis Service Manual

PT-11 CHASSIS ADJUSTMENT

PROCEDURE

l- System Voltage (+B) Adjustment :

- Before switching on TV, all potentiometers should be adjusted at medium level. Then TV is switched on;

- Adjust all of the analog parameters to minimum with RC

- Adjust Pl trimpot until find +115 V on the cathode of D2 diode

2- AFT Adjustment:

- Place a balloon coil (300 Ohm dc resistance ) parallel to L104

- Apply 80 dB UV 38.9 MHz (39.5 MHz for I ) signal via balloon coil

- Connect a voltmeter to aft pin (pin 9) of IC301

- Adjust TlOl coil until the voltage of this pin being 2.5 V dc

3- Adjustment of G2:

- Apply Philips Test pattern

- Adjust all of the analog parameters to minimum with RC

- Adjust G2 trimpot until seeing two bars on gray scale

4- Horizontal and Vertical Adjustment:

- Apply Philips Test pattern signal

- Center the picture horizontally while picture shifting to right and left with Pl 01,

- Make vertical amplitude adjustment with P602 until seeing top and lower lines of picture will be seen

- Center the picture with P601

5- AGC Adjustment:

- Apply Philips Test Pattern whose amplitude is 60 dB UV to the rf input

- Adjust P102 until find a picture without snowy

6- Focus Adjustment:

- Apply Cross-Hatch Pattern signal

- Find the optimum concentration point between H and V intersection in the middle of screen.

7- White Balance Adjustment :

- Apply Philips Test Pattern signal

- Adjust all of the trimpots on CRT board to medium level

- Adjust color, contrast, brightness to minimum by RC

- Adjust G2

- Apply white pattern, settle in the probe of color analyzer to screen

- Increase brightness until geting Y=lO nits

- Adjust x=270 - 276 nits y=270 - 276 nits via “VR201, VR203, VR205”

- Increase brightness and contrast until Y=90 - 100 nits

- Adjust x, y to same values via “VR202 and VR204”

- Check white balance at high and low contrast level. Again make adjustment if it’s necessary.

PT-11 Chassis Service Manual

SPEClFlCATlONS OF Tk&E CONNEGTOR (EURO SCART)

I- Audio output 1. right channel 0.5 VRMS/cI k 0 2- Audio input 1. right channel 0.5 VRMS (connected to No.6) 3- Audio output 2. left channel 0.5 VRMS (connected toNo.1) 4- GND (audio) 5- GtiD 6- Audio input 2. left channel 0.5 VRMS/>lOk 0 7- RGB input, blue (B) 8- Switch signal video (status) 9- GND

lo- Reserved for clock signals (not connected)

1 l- RGB input, green (G)

12- Reserved for remote control (not connected) 13- GND

14- GND switch signal RGB 15- RGB input, red (R) 16- Switch signal RGB 17- GND (video)

18- GNDlS- Video output 1 Vpp/75 ohm 20- Video input 1 Vpp/75 ohm 21- Shield

2 4 6 8 10 12 14 16 18 20

PT-7 1 Chassis Service Manual

AULT TRACBNG DIAGRAM-POWER SUPPLY

important Service Note : Before changing a component in the Primary Mains Stage it is imperative,

that C5 is discharged by a resistor

Attention! A short circuit transistor

Rl .Ql

r-1 short circuit

I /

I i._-.. ._. _

1 YES

R2.11

Q 602

Measure +115 V supply

___ ..--

Pl .RS,ZDl .

supply 165-270V

PT-11 Chassis Service Manual

ROUBLESHOOTlNG GUIDE FOR MAIN PCB

- -._

TROUBLE CHECK POINTS

No color

No vertical deflection Vertical linearity Vertical size

1 Vertical shift 1 Horizontal linearity / Horizontal size / Flue picture /picture 1 Noise picture

_--

Vert./horizontal synchrony

Interference

No sound

Low sound

( Sound distortion

Contrast

Brightness

’

Color saturation

Tuning

Memory

Band select

! No video-out on the SCART

No video-in on the SCART

No sound out on the SCART

1 No sound in on the SCART

No remote control reception Check signals on pin 3 IROland 1301 pin 35

I I

1101, T102, C127, 1102, check pin 38SSC Check +K, 1601, pin 42 1401, pin 43 C 625, R 623 C 625, R 624 R 626. P 601 L601, C608 +B, C 607, L 602 1101 pin 25, ABL, FOCUS, HEATER, EHT 1101 pin 17. SCREEN. EHT. +M TUOl, AGC, IF, Fll 01 1401 TUOl. IF. FllOl Check 1101 pin 5 and pin 50, 1401 1101 pin 5, pin 50. 1401 pin 5. +G, 1401, +G, R 403 1301 pin 5, 1101 pin 25, ABL 1301 pin 3, 1101 pin 17 1301 pin 4, 1101 pin 26 1301 pin 1, Q 301, +D, TUOl I 302, I 301, SDA, SCL I 301 pin 7/8. I 303, +K, TUOl Check TV-VID signals, Q 651 Check 1301 pin 12, 1101 pin 16 on AV mode, check the video signals on AV mode SCART pin 20 and 1101 pin 15

I1 01 pin 1, Q 653 . Q654

Check the audio signals on SCART pin 2/6 and 1101 pin 6

1401

pin 3, pin 5, +G R 403

/ i I

PT-11 Chassis Service Manual

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PT- I 1 Chassis Service Manual

DESCRiPTONS OF THE PARTS

I- SWITCH MODE POWER SUPPLY STAGE

In order to supply the DC voltage required at various parts of the chassis, a SMPS transformer controlled by the IC TDA 4605 and switching transistor 3N90 is used. Cl, EMl, C2 filter circuit prevents the network noises and the effects of high frequency which produced in TV set. After rectifying DC voltage is filtered by using C5. The stat up voltage of TDA4605 is obtained from R2 at the same time a square wave ii produced from pin 5 of IC TDA4605. This square wave reaches QI passing through R8. After that Ql form and induction on TRl. which produces a voltage on pin 6. This voltage rectified by D6 is used as a supply voltage of IC 1. IC 1 does not operates SMPS by stopping pulses at pin 5, when the network is higher or lower than fixed limits. Pin 2 is control pin of overload. This stage produces 115V for FBT, 12V for audio part, 33 V for tuning circuit W,

12V (tuner and some ICs) and 8V (for TDA8362) are produce by the means of the regulators LM7805. LM317 and LM7808. This circuit operates between 165 VAC and 250VAC (50Hz).

29 MiCROCONTROLLER STAGE

Below items are controlled or generated by means of these controllers.

fo CTV 32.25 V2.0 (for mono models) and CTV 352s V1.4 (for stereo models) are used as controller on PT

chassis.

0 Voltage synthesis tuning

+ On screen display

3 Control of two transmission standard

0 Controls of the simple text or fastext decoder

+ Full peri-TV (&art) switching and double scat-t switching on stereo models,

0 Controls of stereo decoder TDA 9840 as German Stereo Decoder

9 SAA 7283 as Nicam decoder

Q Sound processing (Bass, treble, balance)

a Controls of the analog values of the picture (Brightness, Color, Contrast)

3- ANALOG OPERATION PART WITH TDA 8362

TDA8362 is a single-chip TV processor which contains nearly all small signal functions that are required for

color television receiver. Fora complete receiver the following circuits need to be added a base-band delay Ii-

ne (TDA4665) a tuner and output stages for audio, video and horizontal and vertical deflection. TDA8362 can

handle signals with positive modulation and it supplies the signals which are required for secam decoder

TDA8395.

VlDEO IF AMPLIFIER

The IF amplifier contains 3 AC-coupled control stages with a total gain control range of greater than 60 dB.The

reference carrier for the video demodulator is obtained by means of passive regeneration of the picture

carrier. The external reference tuned circuit is the only remaining adjustment of the IC.

In the TDA8362 the polarity of the demodulator can be switched so that the circuit is suitable for both positi-

ve and negative modulated signals. The AFC circuit is driven with the same reference signat as the video de-

modulator. To ensure that the video content does not disturb the AFC operation a sample and hold circuit incorporated: the capacitor for this function is internal. the AFC output voltages 6V. The AGC detector operates on levels, top sync for negative modulated and top white for positive modulated signals . The AGC detector time constant capacitor is connected externally.

PT-11 Chassis Service Manual

SOUND IF CIRCUIT

On mono models;

The sound bandpass and trap filters have to be connected externally. The filtered intercarrier signal is fed to a limiter circuit and is demodulated by means of PLL demodulator. The PLL circuit tunes itself automatically to the incoming signal, consequently, no adjustment is required.

The volume is DC controlled. The composite audio output signal has an amplitude of 700 mV RMS at a volume control setting of -6 dB. The de-emphasis capacitor has to be connected externally. The non-controlled audio signal can be obtained from pin 1 via a buffer stage. The amplitude of this signal is 350 mV RMS.

The TDA8362 external audio input signal must have an amplitude of 350 mV RMS. The audio/video switch

is controlled via the chrominance input pin.

On stereo models;

On stereo models, the adjustable sound output pin (pin50) is used for mono sound. An external sound IF circuit TDA3845 is used for NICAM B/G, I stereo systems. For NICAM L stereo system, TDA4470B Sound IF IC

is used so that obtain AM sound and NICAM I sound carrier. On German Stereo system, TBA120U is used

as FM demodulator for second sound carrier.

SYNCHRONIZATION CIRCUIT

The sync separator is preceded by a voltage controlled amplifier which adjusts the sync pulse amplitude to a fix level. The sync pulses are then fed to the slicing stage (separator) which operates at 50 % of the amplitu-

de. The separated sync pulses are fed to the first phase detector and to the coincidence detector. The coinciden-

ce detector is used for transmitter identification and to detect whether the line oscillator is synchronized. When the circuit is not synchronized, the voltage on the peaking control pin (pin 14) is LOW so that this condition can be detected externally

The IC TDA8362 contains a start up circuit for the horizontal oscillator. When this feature is required a current of 6.5 mA has to be supplied to pin 36.

COLOR DECODING

TDA8362 contains PAL and NTSC decoder (TDA8361 contains only PAL decoder) but it can cooperate with the secam add-on secam decoder TDA8395. The communication between two IC’s is achieved via pin 32. The TDA8362 supplies the reference signal (4.43 MHz) for the calibration system of the TDA8395, identification of the color standard is via the same connection. When a SECAM signal is detected by the TDA8395 the

IC will draw a current of 150 uA. When TDA8362 has not identified a color signal in this condition it will go in-

to the SECAM mode, that means it will switch of the

R-Y and B-Y outputs and increase voltage level on pin 32.

41 VERTICAL DEFLECTION CIRCUIT WITH TDA3653B

The TDA3653B is vertical deflection circuit for drive of various deflection systems with currents up to 1.5 A pe-

ak to peak. Pin 5 is the output pin. the supply for the output stage is fed to pin 6 and the output stage ground is connected to pin 4. Pin 1 is the input for the driver of the output stage . The signal at pin 1 is also applied

via external resistors to pin 3 which is the input of the switching circuit. When the flyback starts, this switching

circuit rapidly turns off the lower output stage and so limits the turn-off dissipation. It should be noted that the lowest voltage at pin 8 is > 2.5 V, during normal operation.

I “4 I I ‘“-

J p 5v

12.5v

SMPS STAGE ClRCUlT DIAGRAM

PT-11 Chassis Service Mawa/

5- HORfZ6NTAL DRIVE CIRCUIT Tl~e horizontal drive pulses obtained from pin 37 of the TDA8362 are connected to base of Q601(2SC: 57i;1

via R602 Q601 drives Q602 (BUH515D) via the drive transformer TR602. TR601 is the EHT transfon>er. r B i 115 V ) is switched by Q602 and TR601 generates both “EHT, FOCUS, G2 voltages required for CPT” and “170 V. Heater voltage and 26 V vertical supply voltage”. The anode beam current information from per’ 7 of TR601 is used for reducing contrast at too high beam currents, in order to stabilize the voltages dew& from power supply.

PT-1 I Chassis Service Manual

61 SOUND OUTPUT STAGE

.On mono models, TDA7056A is used as sound output amplifier with DC volume control. Pin 50 of the

TDA8362 is AC coupled to the input pin 3 of the TDA7056A via a RC filter. It is supplied by + 12V coming from a separate winding in the SMPS transformer.

On stereo models, TDA7057AQ is used as sound amplifier. The sound level is controlled by sound processor TDA8425 via 1% bus on stereo boards. The outputs of TDA8425 ( pin 9 and pin 13 ) is connected to TDA7057AQ via a divider circuit and two capacitors.

71 TELETEXT STAGE

The teletext stage consists of I SAA5254. On this stage, it should be paid attention that there is video signal on pin 8 of I SAA5254 after a RCL filter, on condition that existence of the other requirements such as +5V, periferical components.

Basically, fastext stage consists two l’s, STV5346 Teletext decoder and CTV 974 fastext controller with 1% bus interface. For List Mode a 2K EEPROM (PCF8582) can be added.

81 CRT STAGE

The TDl6103Q is used on CRT stage as video output amplifier. The TDA6103Q consists of three monolithic video output amplifiers. Each amplifier can be seen as an operational amplifier with negative feedback. The

advantage of negative feedback is that the amplifier characteristics do not play an important role up to certain frequencies.

The device needs only one power supply voltage (+M ). In contrast to previous types of DMOS video amplifiers, the TDA 6103Q does not need a second supply voltage (12V.), so it saves one wire from motherboard to CRT stage.

As the TDA 8362 has no white point adjustment and no black current set-up, two adjustments are required for gain and three adjustments for black setting.

PT-11 Chassis Service Manual

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