It will be normal for home televisions to have a few glitches for a long time. The common fault is that televisions have no sound and there is no picture. Faced with this kind of situation, it will be very embarrassing. I do not know what causes it. I do not know if it is necessary to change a TV again. The machine should still be repaired...
Next, Xiao Bian will teach you a few simple ways to tell you what to do if you have a TV with sound and no image.
There are many reasons why there are no images on the TV. For some small reasons, there is no image on the TV. We can find the problem on our own and we can repair it without trouble.
The specific maintenance methods for the television without sound are:
1. Listen to the high-voltage sound of the start-up: If there is a description, the circuit work is basically normal (note that it is basically normal), and if not, the line circuit is not started.
three conditions:
(1) No change, indicating that the cathode voltage of the cathode of the kinescope is abnormal; check whether the 200v visual discharge power supply is normal.
(2) Vertical one bright line because of the open circuit of the horizontal deflection coil or the phenomenon of false welding in the solder joint.
(3) There is a bright line at the level, and there are many reasons. In addition to the open circuit of the field deflection coil or the welding of the welding spot or the welding of the field output block, the signal transmission circuit of the field oscillation and the field output may cause malfunction;
When the output power of the field output block and the peripheral circuit have no abnormalities, adopt the human body induction signal injection method (take the tweezers touch input terminal of the field output block) to observe whether the horizontal bright line has a phenomenon of jumping or broadening; if there is a field output The block works normally, the fault is in the field oscillation, and the signal output circuit of the field output, otherwise the fault is in the field output block itself.
If the picture tube is still on, check the IF channel and the preview discharge, which is usually caused by the detuning of the AFT AGC or the preview 6.5 notch.
If the picture tube is not bright, first see if there is high pressure, there is proof that the line is working properly, and then see if there is a filament voltage of 6.3 volts, and then check the three visual discharge tubes.
If all of the cutoffs are generally around the decoding block fault, check the brightness of the channel and pay brightness potentiometer, this card of the TV picture tube is rarely bad, the worst tube is Samsung. It is not difficult to repair
Is the tube bright when there is no image?
If the picture tube is still on, it should be a fault in the circuit related to the video channel.
If the picture tube is not bright, it may be a failure of the power supply circuit of the kinescope.
In the case of old color TV, if the worst case is that the kinescope is not lit and there is sound, if the picture tube is broken, then the kinescope will be considered “wastefulâ€.
1, brightness, contrast closed.
2, no acceleration voltage or too low.
3, the tube filament does not shine.
4, no high pressure or high pressure.
Check if the filament voltage is present. Yes, the picture tube is bad, otherwise it is the problem of power supply to the filament. The current limiting resistor, rectifier, and filter capacitor are usually broken for the filament supply (part of line output).
CRT filament wire breakage detection method
When the power is turned on, the rear of the picture tube does not emit light and is turned off. Place the multimeter in the Rxl block. The red and black pens respectively measure the resistance of the two pins of the HY5PS1G831CFP-S6C. Normally, the resistance should be about 6 to 10 Q, as shown in Figure 3-85. In order to measure the resistance of the filament of a picture tube, it is about 6Q. If the resistance of the filament is in a high-impedance state or even fails, the internal contact of the filament is bad or has broken.
Cathode cathode emission capability detection method
Detection: When the TV or color display image color cast or a serious color cast, it may be that the individual cathode of color TV display tube produces weaker thermal electron emission. At this point, the voltages at the b-pole and c-pole of the last-stage view-discharge tube can be measured first. If the voltages at the b-poles of the three view-discharge tubes are the same and the voltage at the c-pole is also similar, then the cathode-ray emission capability of the color cathode ray tube becomes smaller.
At this time, the current of each cathode can be further measured. The normal current is generally about 0.4 mA. If a cathode current is less than 0.36 mA, a significant color cast will be produced, and if it is less than 0.3 mA, a serious color cast will occur.
Treatment: If a certain cathode current is 0. 35mA or more, then the color cast only needs to fine-tune the drive potentiometer and white balance potentiometer of the cathode view tube, so that the cathode current is 0.25 ~ 0.35mA, when the adjustment potentiometer can not Solve, can connect a 510{1～lkQ resistance between this cathode and +12V power, in order to strengthen the electric current of this cathode;
If a cathode current is less than 0.2mA, the color picture tube cannot reproduce the normal color, and only the replacement of the same color picture tube can solve the problem.