The original issue with the Hisense TV model TC25100H was a bright line on the screen. During the initial diagnosis, I checked the power supply circuit using LA7841, and it was functioning normally. The 5th pin of the LA7841 showed a bright signal, which indicated that this component was likely not the cause of the problem. I then focused on the field oscillator section. After checking the LA76818 power supply and its surrounding components (pins 23 and 24), everything appeared normal. This led me to conclude that the fault was due to a faulty LA76818.
Since I had an LA76810 on hand, I decided to try replacing it. Although I knew they are often considered interchangeable, the bus settings needed to be adjusted accordingly. After the replacement, the screen started flashing, which suggested a mismatch between the ICs. While the system could enter the menu, there was no "IC SELECT" option available.
I removed the LA76810 and felt reluctant to give up, so I tried adjusting some related data settings close to the original configuration, but nothing worked. Then I considered replacing the CPU. The original CPU was LC863528 3PR5, and I had an LC863524 55L7 as a backup. After comparing the pinouts, I found them to be mostly compatible. Notably, the LC863524 55L7 had the "IC SELECT" option enabled.
Replacing the CPU with the LC863524 55L7 resulted in a full-screen display, although the field size was slightly larger than expected. The screen still flickered, but I managed to enter the menu. The characters displayed were white, indicating that only the blanking signal was being sent. I first adjusted the field width to make the characters visible, then changed the "IC SELECT" setting from 76818 to 76810. Immediately after, the screen stopped flickering.
Next, I checked the color output. It turned out that the R, G, and B signals were not properly reaching the LA76810. In the original setup, the CPU's R and BG signals passed through VD736, VD738, and capacitors C775, C776, and C777 before reaching the LA76810. However, with the new CPU (LC863524 55L7), the signal path included a 4.3K resistor connected to C75, C776, and C777. After making the necessary adjustments, the color output became normal.
Once the video signal was restored, I noticed that only one channel was working. The volume control also didn't function correctly. After fine-tuning the bus settings, everything returned to normal operation. You can see the results in the attached images.
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Hisense TV TC25100H replacement CPU example (LC863524 replacement LC863528) - Home Appliances
AC to AC Power Supply refers to an electrical device that converts alternating current (AC) from one form to another, typically varying the voltage, frequency, or phase of the input AC signal to produce a desired output AC signal. This type of power supply is used in applications where a specific AC output is required that differs from the available AC input.
AC to AC Power Supplies find applications in various industries and scenarios, including:
Industrial Automation: Where different machines and equipment require specific AC voltages and frequencies.
Renewable Energy Systems: For interfacing renewable energy sources (e.g., solar, wind) with the grid or local loads, often requiring frequency and voltage matching.
Testing and Measurement: In laboratories and testing facilities, where precise control over AC power conditions is necessary.
Aviation and Maritime: For powering sensitive equipment on aircraft and ships, where stable and reliable AC power is crucial.