Xiu Cai repair TV: the first time encountered many years of failure (Panasonic TV) - Home Appliances

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My friend's friend blew my phone last night, saying that the TV set in his workshop was broken for a few days, missed a few football matches, and asked me to help anyway. To be honest, last night's game Germany VS Argentina is my favorite team. If you go to repair TV, it means that some wonderful shots are about to be missed. But there is no way to save people’s lives and build a seven-level float. Although reluctant, there is no way to get rid of it, ask the model clearly, and pack up the guy accessories.
This is an aluminum alloy workshop. In the so-called office, a Panasonic 25V42G is lying there quietly, as if silently telling its former glory. It is estimated that it will soon be retired, replacing it as the current popular LED bar. ?
Disassemble the three without it, first test the tube, it has been broken. Do you think that there is no wind and no waves? Carefully check the relevant reverse-pass capacitor (this machine likes to break through the reverse-pass capacitor), the correction circuit, the crystal oscillator, etc., and there is no abnormality. Take a closer look, the previous repairer has canceled the protection circuit, TNND, no wonder it will break through the line tube (the local protection circuit is very sensitive), restore the protection circuit, disconnect the high voltage package + B feet, + B145V is as stable as Taishan, Eliminate the possibility of power anomalies.
Detecting the line current, the string rises to more than 800 ma, the circuit is implemented to protect, it seems that there are still problems in the line.
Several places that can cause overcurrent have been denied, and the rest is the high voltage package! Careful observation, the high voltage package seems to have signs of breakdown near the focus and acceleration poles. With a scorpion pick, it has already burned into a carbon shape. It seems that the high pressure package has been heroic.
At present, this kind of high-pressure package market is almost out of stock. Fortunately, the apprentice has an old machine, and a phone call will be sent in less than 30 minutes. Whether he is free or not, he will be installed.
Turn on the machine, check the line current, 320ma, the filament is bright, and hijacking, I thought it would be done. But the screen did not reflect, more than ten times more than the face of the big bag of adults! Raise the accelerating voltage, the screen is still "the mountain is still the mountain, the beam is still the beam", a little face is not given!
Detecting the three-shot output of the tailgate, RGB is about 160V, obviously the output circuit has an output. Then check the ABL resistor R522 (22K), the resistance is normal, this is amazing! If the luminance signal channel is abnormal, it should be responsive to turn up the accelerometer screen. It seems that the problem is still in the high-voltage package itself, and the apprentice said that when the TV was acquired, it was like severe aging, and the high-voltage package was absolutely OK.
Judging by experience, it is possible to focus on the problem. Open the socket cover and use 10K to measure the resistance of the focus line to ground, which is less than 3K! Unplug the high voltage package to focus and accelerate the lead. The focus of the focus is infinite. At this time, the apprentice removes the stem and opens the inside of the focus pin. The tube seat that appears in front of the eyes is full of sorrows and misery. Black carbon has been burned between the foot and the grounding foot, no wonder so! The TV that has been repaired for many years has encountered this phenomenon for the first time. The serious leakage of the focusing pole and the grounding pin causes the focus voltage to be short-circuited to the ground, causing a black screen without a grating!
Change the tube seat, turn it on, everything works! I asked the user whether the image is blurred every time the TV is turned off before the TV is broken. Will it be clear after a while? He said yes, at first, it was a few minutes. Later, it took nearly an hour to see the image. The indicator light was on a few days ago, thinking that the image would be as long as usual. Who knows waiting, the lights are gone. . I shook my head and said that you guys are usually sick and not ill, and they will have to pay big money when they are seriously ill! A simple header failure is caused by your neglect and even the high voltage package is burned.
Pack the guys, the game of Germany VS Argentina is about to start, hahaha! The user will stay together to watch the game, okay, he will call you bleeding!
Remind the maintenance novices: three no color TV, generally check to the tube breakdown, in addition to the user has used the TV for a long time, there are often reasons, first of all must be carefully checked whether + B is elevated? Then carefully check the reverse capacitance and correct the relevant circuit of the circuit. If the crystal oscillator is used, it must check whether the crystal oscillator is leaking, whether the excitation is normal, etc. Otherwise, if the upstream tube is turned on, the tube may be burned again, causing unnecessary loss. In addition, using a universal meter to detect the line current, a slight abnormality, immediately disconnect the test leads, is also one of the ways to protect the line tube.