Akai 21CT32 colour TV -How to enter the service mode, full circuit diagram - TDA9381, KA5Q1265, or 5Q0765RT STR, 2SD1866 Horizontal Output Transistor.

 

Signal process
The main chip is N301 TDA93X1 AV control switch HEF4052, sound driver is N101
N17821A
The TV signal inputs into the tuner (A101) from CABLE or antenna. The pin 10 and pin 11 of the N301 are combined to select the band. The pin 4 of the N301 outputs the PWM tuning signal. The IF video signal comes from the IF pin of the tuner. The 38.9MHz IF signal is coupled to the V308 (pre-amplify) and then to SAWF (Z301). After processed in the SAWF, the 38.9MHz signal gets to the pin 23 and pin 24 of TDA93X1. The IF circuit in TDA93X1 includes such unit as the AGC amplifying
circuit, 38.9MHz oscillator, PLL video demodulator, video amplifier, IF identify circuit and AFT circuit. The demodulated signal (CVBS) comes from the pin 38 of TDA93X1, the sound signal comes from the pin 44.The internal CVBS signal needs norm identification then outputs from the pin 38 of TDA93X1, via the trap-wave circuit (composed of the V351, Z354, Z352) feeds back to the pin 40 of TDA93X1. The RGB signal comes from the pin51, Pin52, Pin53 of TDA93X1, and outputs to the CRT board.
The internal sound signal comes from the pin 44 of TDA93X1, via the coupling capacitor C367 connects to the pin 3 and 5 of TDA9859. The TDA9859 is the audio effect processor, the AN7522N is the driver. The TDA9859 includes bass, treble, balance, surround, effect shortcut options.
Through Synchronous separating circuit, the video signal is divided into horizontal-Synchronizing signal and Vertical-Synchronizing signal. The horizontal-Sync pulse coming from the pin 33 is transferred to the horizontal-drive transistor, and will be used to drive the horizontal-transformer. The horizontal-switch transistor is V451, it and the +B supply drives the fly-back transformer to generate the anode high voltage, the focus voltage, the screen voltage, the CRT board drive voltage 180V, the vertical drive voltage 15V and -15V.
The vertical sawtooth wave is generated on the pin 21 and 22, and then enters the vertical output amplifier circuit. The vertical output amplifier circuit is realized with the power amplifier IC –LA78040.
The TDA8177 is a 7 pins vertical deflection circuit (2 Amperes) for DC-coupled 90° or 110° deflection systems with frame frequencies from 50 up to 120 Hz. Only a single supply voltage for the scan and a second supply for the fly-back are needed.
The vertical drive currents of N301 pins 21 and 22 are connected to input pins 1 and 7 of the TDA8177. The currents are converted into a voltage by resistor R405. Pin 2 is on a fixed DC level (internal bias voltage, about 2.3V) and on pin 1 the drive voltage can be measured (typical 1.4 Vpp). The outputs (pins 4 and 7) are connected to the series connection of the vertical deflection coil and feedback resistor R404 and R406. The voltage across R404 and R406. is fed via pin 1 to obtain a deflection current which is proportional to the drive voltage. The supply voltage for the TDA8177 is 17V at pin 3. The flyback generator has a separate supply voltage of V on pin 6. On pin 4 a vertical guard signal is available. For HF loop stability a damping resistor R407 is connected across the deflection coil.

Power supply [SMPS]
The IC of KA5Q0765RT is adapted in this chassis; it is the product of Fairchild. It supplies four DC voltages, one is the +B＝ 110V, another is Hcc＝ 26V, the third is 13V (the sound drive voltage), the fourth is +16V. The +16V can generate the +8V, +5V and +3.3V by the special generators.

I2C bus control adjustment method: Enter and exit factory mode

With factory remote control – Continuous push [test] key on the remote controller, the TV mode will change as:

Normal > M > BUS OPEN you can select “M” ( factory mode ) or “normal” mode.

2) With user remote control
Push [menu] key → display picture manual → push digits key 8500 → display M.
Push [standby] key , exit factory mode and TV will be standby.

Menu-8: Geometrical adjustment .
Receive standard Crosshatch pattern signal for PAL system .

1) Adjust VSLOPE value, the horizontal line just appear from half bottom shadow.
2) Adjust VSHIFT value, the center horizontal line correspond to CRT vertical center.
3) Adjust Vamp value, to get 90% of vertical picture contents would be displayed on CRT.
4) Adjust HSHIFT value， to get the picture horizontal center correspond to CRT horizontal center.
5) Receive standard Crosshatch pattern signal for NTSC system, and again adjust.

Menu-7: AGC-TOP adjustment
Receive 60dBu (1mv)VH color bar signal， adjust AGC value (voltage from high to low）， to picture noise reduce gradually to be just disappeared.

MENU9 CRT cut-off and white balance and sub-brightness adjustment.
Receive gray and white 2 steps signal.
a) CRT cut off adjustment.
1. Push [▲P+][▼P-] key to select “SC”, push [►V+][◄V-] key then automatically vertical scan will be stopped.
2. Adjust SCREEN control on Fly-back transformer to get the darkest single horizontal line (red green or blue, sometimes shows more yellow, more purple or more white).
3. Push [V+][V-] key again, vertical scan work repeat.

b) White balance adjustment

1. Select RD/BD menu.
2. Adjustment RD/BD to get color temperature as x=281, y=311.
c) Sub-brightness adjustment (use stair case signal)
1. Select SB MENU.
2. Adjust SB to get the darkest step being on or off.

MENU6 Set SHIP MODE
Select “SHIPMODE”， push [V+][V-]key may be shipped.
Note::
May increase the screen of FBT current, the darking single ought no fly-back line, AV state.

BUS control adjustment item default setting (21 inch)

Note1:
TEXT DEF : TXT_def = 0: Pan_Euro + Cyrillic
= 1: Farsi English + French + Turkish
= 2: Arabic + English + French + Turkish
= 3: UKRAINIAN
Attention:
When TXT_def=0, will appear" the TXT LANGUAGE" in the customer Setup menu, press V+/ V- key," the TXT LANGUAGE" will appear the following circulation: W- TR-> EAST1-> EAST2-> W- TR
The W- TR diagram text includes the following language:
English German Swedish/Fin/Dan/Hungarian Italian French Spanish/Portuguese Turkish
The EAST1 diagram text includes the following language:
Polish German Estonian Slovenian Czech/Slovak Rumanian
The EAST2 diagram text includes the following language:
Polish German Swedish/Fin/Dan/Hungarian Lettish Russian Slovenian Czech/Slovak Estonian
Note 2:
Make use of 4 color keys of the remote control, browse 4 pages of the enactment quickly, namely index function.
The TV/ AV sets the saving key for the index.
While using this function," the TXT LIST" establishes for" ON" in the customer menu.
Example: if want to use the color key of the red quickly 230 pages of enter the diagram text
The sequence press" TEXT"," red key","2","3","0" on the remote control," TV/ AV"
Note 3:
Switch on the hour appearance constitution
0: connect the AC power, enter to need the machine appearance automatically
1: connect the AC power, automatically switch on appearance
2: connect the AC power, if shut down the appearance as the diagram text
appearance, enter the diagram text appearance automatically.

Schematic diagram of the general UOC chassis

LG LH-T7652SB, LHS-76SBC, LHS-76SBS, LHS-76SBW DVD-CD RECEIVER How to enter the service mode, Schematic diagram, Exploded view

 

Stereo mode 100W + 100W (Rated Output Power 100W, 4Ω at 1 kHz, THD 10 %)
Surround mode Front: 100W + 100W (Rated Output Power 100W, THD 10 %).  Centre: 100W
Surround: 100W + 100W
(Rated Output Power 100W, 4Ω at 1 kHz, THD 10 %)
Subwoofer: 200W (Rated Output Power 150W, 3Ω at 30 Hz, THD 10 %)

Be sure no power is applied to the chassis or circuit, and observe all other safety precautions

* NTSC model doesn’t have VCR option and use DVD option B~F as VCR option. (only DVD exist)
* PAL model has another separate VCR option. (Both VCR and DVD exist)

1) The pick-up incorporates a strong magnet, and so should never be brought close to magnetic materials.
2) The pick-up should always be handled correctly and carefully, taking care to avoid external pressure and impact. If it is subjected to strong pressure or impact, the result may be an operational malfunction and/or damage to the printed-circuit board.
3) Each and every pick-up is already individually adjusted to a high degree of precision, and for that reason the adjustment point and adjustment screws should absolutely never be touched.
4) Laser beams may damage the eyes.
 Never permit laser beams to enter the eyes.
 NEVER switch ON the power to the laser output part (lens, etc.) of the pick-up if it is damaged.

NEVER look directly at the laser beam, and don’t let contact fingers or other exposed skin.

Cleaning the lens surface
If there is dust on the lens surface, the dust should be cleaned away by using an air bush (such as used for camera lens). The lens is held by a delicate spring. When cleaning the lens surface, therefore, a cotton swab should be used, taking care not to distort this.  Never attempt to disassemble the pick-up spring by excess pressure. If the lens is extremely dirty, apply isopropyl alcohol to the cotton swab.
(Do not use any other liquid cleaners, because they will damage the lens.) Take care not to use too much of this alcohol on the swab, and do not allow the alcohol to get inside the pick-up.

Service mode entry for EEPROM

SMPS Schematic

Main board schematic

Cabinet and mainframe Exploded View