Repair the old Skyworth power board

DIAG

Repair the old Skyworth power board [Copy link]

 

Or just open a separate thread!

It was still the old Skyworth TV. The fault phenomenon was that it could start up normally and the TV programs would turn off automatically after a few minutes. There was no fault and the power indicator light was not on. After a few minutes, the program could be automatically restored. It was judged to be a power supply problem. The 5V power supply was only about 3.4V after removing the shell and measuring online. It was only about 4.5V under normal circumstances. After replacing the bulging capacitor, the fault still existed and finally it could not start up at all. The
power board was repaired offline. The 5V power supply chip is P1014AP10. I forgot whether pin 1 supplies 7.8V or 8.8V. Then I looked for the TL431 chip and found the sampling resistor between its pins 1 and 2 and the output power supply. It was found that the resistance of R664 had changed (the board was not tested and was all white glue. It was more than ten kilo-ohms after being removed). The silk screen was 242 (chip). The voltage divider resistor is R660, and the silk screen is 2491 (about 2.5K measured online). Fixed resistor plus adjustable resistor, adjust the output voltage, remove and measure the resistance value,

Discrete components are spliced with a close resistor,

After installation, it is OK.
Note: It is best to add an isolated power supply when repairing the power board! ! !

When I searched for the fault online, I found that the circuit diagram of the power board was quoted from the home appliance repair information website.

tagetage

Good maintenance experience.

There are no three faults and the power indicator light is not there-------What do three faults mean?

wangerxian

This old item feels very comfortable after being repaired.

qwqwqw2088

The power supply problem is more accurate.

秦天qintian0303

Which part is most likely to break?

eric_wang

More than 10 years ago, I had a Konka LCD TV at home. It had a similar problem. The screen dimmed and then turned off automatically. After a while, it would light up again. Because I had been using it as a monitor screen, I thought it was aging, so I discarded it. Now it seems that it may have a similar problem.

niuyite

Electronics repairman was such an enviable profession 30 years ago, but it has declined with the increasing integration. Occasionally repairing old items is a great blessing in life!

okhxyyo

Great~~~ My TV has been going crazy lately, turning on automatically all the time. I had no choice but to unplug the cable. The so-called smart system automatically turns on. . It's really intoxicating

DIAG

tagetage posted on 2024-8-9 09:39 Good maintenance experience, three no faults and no power indicator light -------what does three no faults mean?

This was the term used in the CRT era. Now it can be understood as no backlight, no image, and no sound.

DIAG

niuyite posted on 2024-8-9 10:28 Electronic repairman was such an enviable profession 30 years ago, but it has declined with the intensification of integration. Occasionally repairing old items is a great blessing in life!

Now they are all scrapped. I just play with them for fun. The original parts are given by Teacher Maychang.

DIAG

qwqwqw2088 posted on 2024-8-9 09:56 The judgment of power supply problems is relatively accurate

Hi, I gave up at first, and the second-hand power supply board I bought online arrived. By chance, I discovered that when I touched the transmitting and receiving ends of the isolation optocoupler, the output voltage changed, so I continued to repair it. It was a lucky coincidence. I'd like to share this with you so that you don't have to make a detour!

DIAG

eric_wang posted on 2024-8-9 10:22 More than ten years ago, I had a Konka LCD TV at home with a similar problem. The screen dimmed and then turned off automatically, and then lit up again after a while, and repeated this process...

It’s right to start electronic repair from the power supply!

DIAG

okhxyyo posted on 2024-8-9 10:35 Like~~~My TV has been going crazy lately, turning on automatically all the time. I have no choice but to unplug the cable. The so-called smart system automatically turns on. . It's really intoxicating...

Hey, the price has come down, but the quality control is not as good as it used to be!

DIAG

Qintianqintian0303 posted on 2024-8-9 10:04 Which part is most likely to break?

The most obvious thing is the bulging of the power supply filter capacitor. The rest requires specific analysis of specific problems. If you study electric vehicle chargers, you will find that the principles of common power supplies are similar.