Akai CT-W2855, CT-W3257 Service Manual

FEATURE STEREO FW-CHASSIS 16:9

@J Service manual @ Serviceanleitung (3 Serviceanvisning

a Manuel de service a Manuale di servizio

CT-W3257 CT-W2855 ENT

UNT-DPL

1997

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Service mode selection:

Switch on the receiver by pressing the mains switch and within 5 s. press the remote control buttons MENU, TV and ‘7” successively.

Wahl des Service-Modus:

Schalten Sie das Gerat mit dem Netzschalter ein und drticken Sie innerhalb 5 Sekunden nacheinander die Fernbedienungstasten MENU, TV und ‘3”.

Val av service-liige:

SIB pa mottagaren med huvudstrombytaren och inom 5 s. tryck pa fjlrrkontrollens MENU, TV och “i” knappar succesivt.

Sklection du mode service:

Mettre le recepteur en marche a I’aide de I’interrupteur principal et dans les 5 secondes appuyez successivement sur les touches MENU, TV et 7” de la telecommande.

Selesione del modo servizio:

Accendere il ricevitore tramite I’interruttore genera+ e premere in sequenza i tasti del telecomando MENU, TV e ‘7” entro 5 secondi.

Language selection

1. Press the MENU button (under the lid).

2. Select “Set-up” with the cursor buttons (up-/downwards) and press the OK button.

3. Select “Language” and press the OK button.

4. Select the desired language and press the OK button.

5. Press the TV button to exit.

Manual tuning

Select programme number you want to tune.

Press the MENU button. Select “Manual tuning” and press the OK button.

Press the red button (SEARCH).

Press the OK button to store.

Press the TV button to exit.

APSi (Automatic Programming System)

1. Press the MENU button.

2. Select “Set-up” and press the OK button.

3. Select “Retune TV” and press the OK button.

4. To retune the channels, press the OK button.

5. Press the TV button to exit.

NVRAM (ICf2)

lnitialization of NVRAM

The NVRAM must be initialized and configured, if the NVRAM is

replaced or it has totally lost its data. The next procedure is

assuming that the tv does not start at all due to wrong data in

NVRAM.

Set the receiver to the service mode by switching on the

receiver with the mains switch and within 5 s. pressing the buttons MENU, TV and ‘7” successively. Note! The receiver is in the service mode although it looks like the receiver is in stand-by mode! Press the RED-button to pre-configurate the set. Green led

will flash once to indicate this. At the same time the controller will check NVRAM and

initializes it automatically if it was “empty”. lnitializing will take about 15s. When it is complet, the green led will light up. Continue to the step 4. The automatic initializing did not happen, if the green led

does not light up steady. In some cases the led might also light up immediately after configuration without any initializing, depending on NVRAM contents. In this case it might be enough to to store the new configuration by pressing “OK”. Continue to the step 4. If the automatic initializing did not happen, you can start it

manually by entering the key code: BLUE (wait approx. 2~1, 2,5,4 (wait approx. 2s) and OK.

lnitializing will take about 15 s. Switch off the receiver by pressing the mains switch.

Set the receiver to the service mode by switching on the

receiver with the main switch and within 5 s. pressing the buttons MENU, TV and 7” successively. If the receiver remains in stand-by mode, press the TV button twice and

then press the ‘7” button.

Configurate the receiver by pressing the RED button. The

configuration menu will show up.

Press the OK button. Press the TV-button and tune in one or more tv channels.

Return to service mode by pressing the “i” button.

After that make all of the service adjustments (see section

10,

“Service adjustments via IIC bus”).

11. Switch off the receiver by pressing the mains switch.

Service mode selection

1. Set the receiver to the service mode by switching on the set

with the mains switch and within 5 seconds pressing the

remote control buttons MENU, TV and “i” successively.

N-1 If the receiver remeins in stand by mods, a&w

selecting thrir service mode, swirch on the receiver by pressing the 734 button tw&e 8ffd &&?ct tbtt swvtce mode

by prerpsing the 7” butt&n.

Option byte description

Bit Description Setting ’ ’

0 TV tuner

1 Decoder TDA9141

4 Deflection controller TDA9151

5 RGB processor TDA4780 6

Video switch TDA6417

7 PIP controller SDA9188

76543210

Yes No Yes Yes No Yes No Yes No Yes

1 ‘0’

In the service mode an adjustment menu (including the adjustment number and name, initializing (left) and adjustment (right))

values are shown on the screen.

2. Return from the service mode by switching off the receiver with the mains switch.

Configuration and fault diagnosis

The set must be configured after adding or removing some options. By pressing the red button in the service mode, the

processor checks all possible addresses of bus-driven circuits and shows the settings on the screen.

This feature can also be used in fault finding; if an option bit is

not “1” when it should be or if it is not possible to change it to “1” by using the number buttons, the IC is either not present or it is

faulty.

Changing the option bytes

1. When in service mode, select the configuration mode by pressing the red button.

0 PIP tuner 2

Megatext SDA5273

5 MSP3410 version D-3B 7

MSP3400 / 3410

0 DSP (AR600)

1 Subwoofer

Comb filter (SVHS line low)

6 DSP (AR602) 7

I/O PCF8574 (DWGxx module)

o-3 Loudspeaker configuration (user mode) 4

Bass splitting (Manual)

6 Pre-equalization for DSP (manual)

0 TXT with external RAM

TOP text enabled (manual)

Flof text enabled (manual)

TXT sync mode (manual)

5 Subpage rolling (manual)

0 Camera connector installed (manual) 3 RGB enabled only in El 4

NTSC 3.58 MHz

5 ACI enabled (manual)

6 NICAM enabled (manual) 7

Loudness enabled (manual)

Yes No

Yes No Yes No Yes

Yes No Yes No Yes No Yes No Yes No

Yes No Yes No Yes No

Yes No Yes No

Yes No Yes No Yes No Yes No

Description

SW VER. = pP software version. NVM VER. = NVM software version.

Select IIC Device byte 1 - 4 or Option byte 1 - 5 with the cursor button (up-/downwards). Selected byte is shown highlighted. Set the bits with the number buttons (0 . . . 7). Store the settings by pressing the OK button.

Return to the service mode by pressing the red button again.

0 Start TV with mains

S-VHS disabled in A/V connector

6 Start TV to demo mode

Hotel TV functions enabled

0 B/G system

I system

D/K system

L/L’ system

Only UHF tuner

3-4 OEM option (manual) 5

Volume bar enabled

On-screen programme number enabled

Parental lock on

Yes

Yes No Yes No

Yes

Yes No Yes No Yes

Yes No’

Remote control buttons in service mode

When the receiver is in service mode you can select the normal TV mode by pressing the TV button and return to the service mode by pressing the “i” button. Number and cursor buttons are used for service adjustments. The yellow button hides temporarely the service menu. The OK button stores the settinns.

Adjustment for different picture format

First make all adjustments with normal 16:9 picture format. The TV uses these adjustment values for all picture formats if no other adjustments were made. In each adjustment it is mentioned if the adjustment must be done separately for different

picture format, repeate only those adjustments.

Making the service adjustment

1. Give a two numbered code which determines the adjustment

(e.g. 05 = horizontal phase, see the following tables) with the number buttons.

Note! The adjustments can also be selected with the

cursor button (up-/downwards).

Vertical picture adjustments

Adjustment

OSD Init.

Zode

name

Vertical amplitude Vertical off-centre shift Vertical start scan

V-ampl. V-shift V-start

2. Adjust with the cursor button (left/right).

3. Store the new value by pressing the OK button.

Note!

l To avoid incomplete adjustments store each adjustment in the

memory immediately after adjusting.

l If the adjustment has to be made separately for different

picture format, select the normal user mode by pressing the TV button and change the picture format with the ZOOM button. Return to service mode by pressing the the “i” button.

Note!

value

Adjust the picture height to correct ratio.

3 6

Vertical S-correction

S-corr.

Vertical S-correction 413 Zoom1

Vertical slope 4:3 Zoom (coarse)

12 Zoom-H 71

Vertical slope 4:3 Zoom1 Vertical slope 4:3 Zoom, 60Hz NTSC

Vertical slope 4:3 Zoom (fine)

Zoom-L

Vertical slope 4:3 Zoom1

Center value, 43 Zoom shift (V-wait)

Shift

Center value, 43 Zoom1 shift Center value, 4:3 Zoom shift, 60Hz NTS

Horizontal picture adjustments

Adjustment

EW width

Horizontal phase

:ode

OSD Init. name

Width

H-shift

value

Horizontal phase 4:3

Horizontal phase 4:3 Zoom Horizontal phase RGB Horizontal phase RGB Zoom

EW parabola 06 Parab. 13 EW corner EW trapezium EHT compenzation

07 08 09

Corner Trapez EHT

0 2

Separate adjustments for 16:9 and 4:3 Zoom1 format!

Separate adjustments for 4:3 Zoom and 4:3 Zoom1 format Make the adjustment also for 4:3 Zoom picture using

60Hz NTSC signal!

0 Separate adjustments for 4:3 Zoom and 4:3 Zoom1 format

Separate adjustments for 4:3 Zoom and 4:3 Zoom1 format

Make the adjustment also for 4:3 Zoom picture using

60Hz NTSC signal!

Note!

Set brightness and contrast to 10%.

Separate adjustments for normal 4:3,4:3 Zoom and 16:9 picture format!

In addition make same adjustments by using RGB signal!

Set brightness and contrast to 90% and compensate

the change in picture size.

Other adjustments

Adjustment

Red gain Green gain

Blue gain

Red reference Green reference Blue reference

Clamp shift Peak white limit Gamma correction

Tuner AGC

Power supply block

Supply voltage WI) and protection circuit

Setbrightness and contrast to normal level. Connect a

universal voltmeter to the cathode of Do1 1.

Adjust with Pol the DC voltage (Ul) for +I55 V (fl VI

Code OSD

name

17 R gain 18 G gain

19 B gain

20 R ref. 21

G ref.

B ref.

Clamp 0 Normally no need to adjust. 23 PWL 63 Normally no need to adjust. 24

GAMMA 32 Normally no need to adjust. 25 TVAGC

Init. Note!

value

This procedure is necessary e.g. when the picture

32 tube, CRT-module etc. has been replaced! 32 Apply a test picture and adjust the R, G and B

references.

Then adjust the R, G and B gains. 52 21 16

170 Apply a 1 mV (60 dBuV) test signal. Adjust the picture just

without noise.

LL Picture and sound IF-module

Video demodulator

1. Apply a test signal (I mV = 60 dBuV).

2. Connect a universal voltmeter to the module connector Xl pin 6.

Check the over-current protection after making any service operations in the primary circuit of the power supply. Set the receiver to the stand-by mode. Short circuit the cathode of Do 13 to the ground and keep the short circuit connected. When

the over-current protection works correctly, the power supply

stops. Remove the short circuit and switch on the receiver by pressing the mains button.

K Horizontal deflection block

Focusing

Set brightness to normal level and contrast to high level. Use cross-hatch pattern and adjust the picture for optimum resolution.

(Screen grid voltage) Ug2 voltage

Set contrast to minimum, brightness and colour saturation to normal level.

At the end of the vertical blanking, there is a black current measurement pulse (clamp pulse) at pins 9, 12 and 15 of

IChl. Use an oscilloscope and find the output stage with the highest cut-off (ie. the highest voltage during the black

current measurement pulse).

Adjust the voltage of the clamp pulse to +I40 V with Ug2.

3. Adjust with LL6 the DC voltage to the point where it changes from 0 to 5 V.

Sound demodulator

Apply a CCIR B/G standard (FM modulated sound) test signal.

Connect a universal voltmeter to ICLI pin 13.

Adjust with LLI the DC voltage for +3.7 V.

______ _.L

Clamp pulse v-l_A

140 v

Note! Adjust the voltage with a clamp pulse.

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