Haier television blue screen is how is it? how should I solve this?

Haier television blue screen is how is it? Followed by the author to see what causes Haier TV's blue screen phenomenon, how to quickly repair.
Haier TV blue screen reasons:

1. The condition of the high-frequency head and its selection station is not normal. Cannot receive, select, amplify, or output a normal 38MHz image IF.

2. IF channel (including pre-amplifier, acoustic surface filter, image drop, video detection, preview, AGC, AFT, etc.) is faulty. It cannot amplify and demodulate the video signal normally; or send it to the high frequency head. The abnormal AGC voltage makes the high-frequency head unable to work (because the high-amplitude AGC voltage is the offset of the high-frequency discharge tube in the high-frequency head); or the AFT voltage sent to the CPU is abnormal, and the CPU considers the tuning to be incorrect (not the best State) without saving the station and performing blue screen squelch.

3, TV/AV switching circuit failure. It is not possible to properly switch or transmit TV and AV status signals.

4. The radio identification signal (which can represent the presence or absence of a radio station in the presence of high or low level or pulse or other representative form) forms and transmits a circuit fault. The CPU “thinks” that there is no station and executes the blue screen squelch, mute, and no signal for 5 minutes to 15 minutes. Automatic standby.

5, memory loss of power or damage. Cannot store the normal searched program (memory) and cannot reproduce the picture sound at the next power-on; or the memory data (such as AGC, IF selection, AV channel selection, identification signal mode selection, etc.) is lost or changed, so that the corresponding circuit Can not work normally.
Blue screen fault location and maintenance strategy analysis

1, input AV signal inspection method

When there is a TV "blue screen" fault on Haier TV, if there is a DVD player, it is best to observe whether the video is still "blue screen" from the AV terminal input signal of the TV. The following three conditions will occur:

(1) TV "blue screen", AV diagram, sound normal.

Most of the movement, TV status and AV status of the station identification signal formation, transmission circuit is common, as long as there is a state diagram, sound normal, indicating that this part of the circuit is normal. These malfunctions occur in the color TVs of these movements. The fault location should be in the control circuit of the high-frequency head and its selection channel, the mid-channel, and the TV/AV switching circuit.

At this point in conjunction with the cancellation of "blue screen" and automatic search operation inspection, can further narrow the fault. However, there are also a few movements, TV status, AV status each have a radio identification signal formation and transmission circuit, and the CPU also has two legs as TV status and AV status radio identification signal input terminals [such as the microprocessor in the A6 movement. The LC864512 (42) pin (line synchronization conforms to the gate input) serves as the input signal for the AV status station identification signal, and the (43) pin (SD identification input)] serves as the input signal for the TV status radio identification signal.

For this type of machine, TV station identification signal formation and transmission circuits are also checked when this failure occurs. For the color TV controlled by the I2C bus, it is necessary to enter the maintenance state to check whether the option data of the high-frequency head option, AGC, and IF selection is correct.

(2) Av "blue screen", TV picture, sound normal.

Such failures generally occur in TV/AV switching circuits and AV station identification signal formation and transmission circuits (TV stand-alone, AV state station identification signal formation, and transmission circuit independent devices). The color TV controlled by the IzC bus needs to enter the maintenance state, and check whether the option data such as the number of AV channels and the identification signal mode are correct.

(3) AV and TV are "blue screens."

This type of failure typically occurs in TV/AV switching circuits and radio identification signal formation and transmission circuits. The color TV controlled by the I2C bus also needs to enter the maintenance state to check whether the option data such as the identification signal mode selection is correct.

Cancel the "blue screen" method

When overhauling the "blue screen" fault, in order to expose the nature of the fault and facilitate the observation of noise particles and the situation of getting out of the station, it is usually necessary to temporarily cancel the "blue screen" function. There are several ways to cancel the "blue screen":

(1) Cancel the "blue screen" with the remote controller.

Most models can cancel the "blue screen" by pressing the corresponding button on the remote control. If there are some machines, press the "SYSTEM" button on the remote control to call up the "SYS-TEM (system)" menu and select the "blue background" item to set the blue background on or off, when set to the blue background "on "When there is no signal, there is a blue background display; when set to a blue background "Off," no blue background is displayed.

(2) Disconnect the blanking terminal of the microprocessor and the "blue screen" control terminal to cancel the "blue screen".

The common method is to disconnect the microprocessor's blanking terminal and blue character output. Some microprocessors have a "blue screen" console and should also be disconnected.

(3) Analogue station identification signal input, artificially released "blue screen" squelch and mute microprocessors such as CTV222S, PCA84C640P, PCA84C841/177 (CH5002), TMP47C1638, etc., the input station identification signal is high and low logic level, generally in the absence of The signal input is low (close to 0v) and high (5V or so) when there is a signal input.

For these microprocessors, if a resistor is connected to the radio identification pin and the +5V power supply, this pin is forced high, and the microprocessor thinks that there is a signal input, thus releasing the "blue screen" squelch function. Also cancel the mute function.

Microprocessors such as M37210, TMP47C433, TMP47C1238, TMP87CM38, etc. The input station identification signal is a composite sync pulse or a line sync pulse. To simulate the input of a radio station identification signal, a square wave pulse with a frequency of 15-16 kHz must be externally introduced. The amplitude is chosen to be 4.5-5Vp-p, not more than 6Vp-p) to cancel the "blue screen". This method not only cancels the "blue screen" but also cancels the squelch. However, it is not very convenient in practical operation, so this method is not used much.

After clearing the "blue screen" by the above method, clear images appear to indicate that the fault is in the radio identification signal generating circuit and transmission circuit; if there is no noise (white grating) or very few noise on the raster, the fault is in the intermediate amplifier circuit or TV/ AV switching circuit: If there are more noise points on the screen (snowflake full screen), it means that the fault is in the high-frequency head and the control circuit of the station selection.

After determining the fault range, you can easily use the "interference method" and "voltage, resistance measurement method" to find the fault. If you do not cancel the "blue screen", it is difficult to judge the scope of the fault, and the interference method is also useless.

Perform automatic search actions to narrow the fault

For TV "blue screen" faults, such as canceling the "blue screen" after the noise point is normal, then the automatic search operation, according to the situation further narrow the fault.

(1) Unable to search for radio programs (no response on the screen), indicating damage to the high-frequency head or condition selection circuit (including: supply voltage BM, band switching voltage BL, BH, BU, tuning voltage BT, RF-AGC Voltage) problem;

(2) Only TV programs in a certain frequency band can be searched, and programs in other frequency bands cannot be received, indicating that the frequency band switching circuit is defective;

(3) All TV programs can be searched, but the number of displayed programs cannot be incremented (it is customary to refer to "no station"), indicating that the radio station's identification signal circuit or AFT circuit or CPU is bad;

(4) All TV programs can be searched, and the program number on the screen can be incremented, but the system is turned off and then turned on again. It is no picture and no sound (usually referred to as "no memory"), indicating that the memory is bad or the microprocessor There is a disconnection between the memory and the memory.

Smart TV/box information can focus on smart TV information network sofa butler (http://), China's influential TV box and smart TV website, providing information, communication, TV boxes, smart TVs, smart TV software, etc. Answering questions.

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