The Changhong PF25118 color TV often experiences data error issues, more accurately referred to as data initialization failure. The symptoms include: after a normal shutdown, the next time the TV is turned on, there is no image, no sound, and the channel numbers turn red. However, after an automatic search, the image appears, and the sound can be adjusted to full volume, but the field size increases, and the frame shrinks by about 1cm with pincushion distortion. After performing the following steps—changing OP1 from 3E to F0 and OP4 from 5F to DF—the TV works normally. But after a few days, the same issue recurs. This is a design flaw in the unit. The root cause lies in the mismatch between the line change and the flat picture tube. When the TV is turned on or off, high-voltage static electricity is generated, which can be sensed by the keypad, leading to CPU and memory re-initialization. Observing carefully, you'll notice that the static electricity is especially strong during dry weather, making this issue more frequent at those times. Single Sided Digital Sign,Window Facing Lcd Signage,Digital Lcd Signage,Hanging Ultra-Thin Lcd Digital Signage 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 (though it's unclear if this was originally designed).
2. Prevent high-voltage static from affecting the keypad. This is something technicians can do manually.
Method 1 (provided by Li Tianhao): Connect the button’s ground wire to the CRT’s ground line, coat the button circuit board with insulating varnish, and place the power switch on the outer layer, grounding it via a metal scraping root and soldering it to the CRT ground.
Method 2 (provided by chst): Connect two 4148 diodes to the data and clock lines. Connect their negative ends to +5V and positive ends to ground. Ground the keyboard’s chrome parts to prevent interference.
Method 3 (provided by Xu Xiaofeng): Manufacturers have made technical changes. Locate the 5V connection to the fast storage and replace 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 and ground it. Use four 1N1448 diodes for the 5th and 6th legs of the 24C16 memory chip. Connect the positive poles to +5V and the negative poles to ground.
Method 5 (not provided by the solver): Disconnect pin 7 of the memory, perform an automatic search, adjust settings, and then reconnect pin 7 through a 6.8kΩ resistor to +5V. This method may inconvenience users, such as requiring re-searching for new channels on cable TV and losing stored programs.