Changhong PF25118 color TV often experiences data errors, more accurately described as data initialization failures. The symptom is that after a normal shutdown, when the TV is turned on again, there's no image, no sound, and the channel number turns red. After an automatic search, the image appears, but the volume is at maximum level (100), the field becomes larger, the frame shrinks by about 1cm, and pincushion distortion occurs. Each time this happens, you have to enter the bus, change OP1 from 3E to F0 and OP4 from 5F to DF, then turn off the TV using the remote control. After that, everything works fine, but the same issue reappears every few days. This is a design flaw in this model! The root cause is that the line adjustment does not match the flat picture tube. When turning the TV on or off, high voltage static electricity is generated, which is sensed by the keypad, leading the CPU and memory to reset during startup. If you pay close attention, you'll notice that the high-voltage static electricity is especially strong during these moments, particularly in dry weather. 10.1" - 27" High Brightness LCD Panel 10.1" - 27" High Brightness Lcd Panel,Lcd Module,Sunlight Readable Tft Panel,Auo Panel Shenzhen Risingstar Outdoor High Light LCD Co., Ltd , https://www.risingstarlcd.com
Changhong color TV PF25118 repeated data error common problem - android - Phones Developers
Solutions:
1. Replace the original line with one that includes a high-voltage bleeder resistor (whether the manufacturer designed it or not is unknown).
2. Prevent high-voltage static electricity from affecting the keypad. This is something technicians can do.
Method 1 (provided by Li Tianhao): Connect the button's ground wire to the CRT’s ground line. Then coat the button circuit board with insulating varnish, and place the power switch on the outer layer with a metal scraping root, soldered to the CRT ground.
Method 2 (provided by chst): Connect two diodes (like 4148) to the data and clock lines. The two pins are connected to the positive and negative poles of each diode, then both negatives are connected to 5V, and the positives are grounded. Also, ground the chrome part of the keyboard.
Method 3 (provided by Xu Xiaofeng): Manufacturers have made technical changes. First, locate the connection for the fast 5V storage and remove it, replacing it with an inductor. Then add a capacitor, and apply hot melt glue to the metal parts of the button panel.
Method 4 (provided by laowu2007): Wrap the switch in thin tin foil, ground it with a wire, and use four 1N1448 diodes for the 5th and 6th legs of the memory block 24C16. Connect the positive ends to 5V and the negative ends to the respective pins. The other two positive ends are grounded.
Method 5 (not provided by the problem solver): Disconnect the 7th pin of the memory, perform an automatic program search, adjust color, contrast, brightness, and then reconnect the 7th pin through a 6.8K resistor to 5V. This may be inconvenient for users, such as needing to redo the auto-search for new cable TV channels and losing the ability to remember newly added programs.