Changhong 3D51A5000i is another invincible transfer machine. The fault is not powered. I don't know if you have ever encountered it. Anyway, I have seen many cases!
Measuring the power plug resistance is infinite, it is estimated that the power board is sacrificed! On-site maintenance, did not disassemble, just measured the next sample, then told the internal circuit board failure, maintenance costs gray black brown, agreed to repair, find the car dragged back to the store! Disassemble and repair, the PFC is blown up, and the pipe screws are not on.
The position of the power tube under the board is welded... directly to the cockroach... Big Brother, are you turning off the black bonfire or throwing it directly into the grill to fix it? Look at your welding, I have no eyes! It hurts me to clean up for a long time...
The two power tube models are different. The bad one is 7N80. The other original STP14NK50ZFP is not burnt. Even if there is no problem, you can't replace it with an asymmetrical tube. If you mess up in the post-repair stage, you will be fried early. Going a few streets!
Suddenly, a little black spot caught my attention.
No matter how embarrassing the fault can not escape my eyes! Indeed, my eyes and nose are different from normal people. The nose is particularly sensitive to temperature odors. Some high-temperature components can be used with the nose to feel abnormal. Therefore, when soldering iron is used, it is often smelled and re-welded. Some things are particularly sensitive, such as cracks in the components of the circuit, burnt places, etc. I feel that I can't say it. A board that I have never seen before is placed in front of me. Scanning will reveal some unusual phenomena! A bit like the king of the strongest brain, the microscopic water, but not exaggerated to such a metamorphosis! This is related to an accident more than 20 years ago. At that time, I was a few years old. I was seriously injured in my right eye. I was almost blind. The size of the left and right eyes was obviously different. The black one was 1 meter away. I took the hospital with my size and did not cure it. Finally, the economic reasons can only be abandoned. After school, my left eye began to be affected. There was nothing in primary school. After junior high school, I became more and more nearsighted. Sitting in the middle of the classroom, I saw the words on the blackboard. They are all ghosts. They can't bring myopia glasses. They are dizzy and painful. They are more serious after going to high school. They are listening to the class. There is no way to see what the blackboard is saying. The eyesight falls below 1.0. The hospital examination only said that myopia, did not find a result! But things within 0.5 meters are particularly clear! Therefore, since I was young, I particularly hated the visual examinations held by the school. Every time I was the last one to go to the visual inspection, I was afraid that my classmates would make fun of me, but I was used to making fun of it. I have always been very optimistic, laughing and finishing... ...haha... This doesn't always come this way, the days are not the same, fortunately, vision does not affect normal life and work! Sorry, I suddenly remembered some of the previous things and couldn’t help but write it out!
Follow this path to trace, to correct the inductance feedback sampling pin, obviously there is high voltage coming in from here, or how the resistance can be burned like this, the other way to the power chip SPC1012T, no test, definitely see Zhou Gong went! Blindly replace these, a train IC is not enough for you to burn! Don't miss the most critical step. This power board, whether it is Samsung or Changhong or others, found that there are two faults in the power inductor. The primary and secondary PFC power inductors are prone to short circuit. The main reason is that the insulation is not well done. When the sampling winding and the primary coil are at a high temperature, it is easy to jump! This kind of power board Ma Yun also has those so-called technical upgrades, which are all things that change the soup, N have been opened and compared, they are the same material, just changed the package, because in Samsung The same problem exists in the machine!
The correction inductor is removed and the feedback winding is directly burned open.
Then measure the primary and feedback pins directly short-circuited, you said that you can not fix the blindly installed IC MOS resistors, 300V unobstructed all the way to not let the 1012T blow up the sky?
The air cylinder is heated until the soup is gently pulled, and it is not hard.
Unpack the insulating tape, no need to say it.
Be sure to check that the other one is not broken and handle the insulation to prevent unnecessary repair. The feedback coil is wound back according to the original number. The main coil is cleaned to make insulation, not bad, no need to change, connect the line well. Silicone fixed! Replace the bad 14NK50, check the external components of the G pin, clean the pads to prevent short circuit, replace the SP1012T and burnt resistors. According to the comparative analysis, this resistor 20K is undoubted! To learn to look at circuit analysis components, don't touch the little things, the drawings, and where are the many drawings, like those imported machines without drawings? No matter how I don't understand, I basically don't look for drawings, which is why I don't usually post the drawings.
At the same time, we must check the two 450V capacitors. One of the plates I repaired is halved in size and has slight signs of pregnancy. It is used up as much as the original. The Panasonic board has been removed from the original one. It is a bit too big, barely loaded. On, the silicone is fixed!
After checking again, PS→ON is grounded, VS→ON is connected to 5V, 220V power input is string 200W bulb, VS load is hanging 15W refrigerator bulb, power is normal, then put on insurance, VS hangs 100W, test machine 10 minutes fever Not big
Hang up the thermometer and cover the case for one hour to ensure that the temperature does not exceed 55 degrees.
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Install the back cover and then test the machine one day.
Although it is only 100 pieces to buy a piece, it is much more than a thing you have to learn to change 100 pieces!
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