Disassembling CASIO radio alarm clock TQT-251NJ-7JF

lyg2275

Disassembling CASIO radio alarm clock TQT-251NJ-7JF [Copy link]

 It is said that those who work in model electronics can take home appliance repair as a second career. I have repaired old TVs, induction cookers, alarm clocks, laptops, etc. before, but I didn’t take pictures. This time, when I saw the forum organizing an event, I found the easiest alarm clock to disassemble and took some pictures. A few months ago, my alarm clock was not keeping accurate time. It was off by more than ten minutes in half a day. I took it apart for repair and replaced it with a new crystal oscillator based on my colleague's advice. Now it keeps accurate time. It seems that the remedy is right for my case. Here's a front view first. My daily work has taught me good habits. I turn off the power before I start working. I use three No. 5 batteries. Remove the five screws on the back (you can see they are flat-tail self-tapping screws if you look closely) and unveil the mysterious transparent mask. Continue to remove the four screws on the front (also flat-tail self-tapping screws). After opening it, you can see the internal structure. To be honest, I'm quite disappointed. The internal wiring is messy, which is not at all what I imagined Japanese electronic products should have. PS: I replaced the shiny cable before. I forgot why. Maybe the original cable was messy. I replaced it because it looked unpleasant. An expert can tell at a glance that it is a low-quality domestic cable. However, I didn't have imported cables at the time, so I had to make do with it. The workmanship of the circuit board is still good. It is lead-free. From the two through-hole pads, we can see that the immersion gold process is used. The silk screen is clear on the board, and the detailed information of the board can be seen. It has passed the CEC certification. From the definition of each cable pad, the various functions of the alarm clock are realized through this board, but the main control chip is protected, so we can't see what it is. PS: The red circle is the crystal oscillator I replaced before, 32.768k. It was originally a plug-in. I only had a patch on hand, so I just soldered it on. Anyway, there is no vibration, so I am not afraid of it falling off. This board should be used for receiving waves. It is connected to the magnetic rod antenna. The main chip is also protected. These two buttons are used for lighting. There is a button on the top of the alarm clock. When you wake up at night and want to check the time, just press it and the whole alarm clock will light up. Of course, the alarm clock also has an automatic lighting function, which will automatically light up when the ambient light is dim. This is the light guide ring. Two LEDs are embedded at the upper and lower ends, which can make the entire alarm clock light up. Movement, fixed with buckles on three sides From left to right, they are the alarm hand, hour hand, minute hand, and second hand. To remove the movement, you must first remove these four hands. The inside of the movement is quite complicated, so I dare not start it easily. Overall, the workmanship of this alarm clock is good, but the internal wiring is a bit messy, and it stopped working after one year of use. I don’t know if it’s because it’s made in China, or if I bought a fake. I also have a Casio radio-controlled wall clock at home. I haven’t changed the battery for five years, and it’s still very accurate. Next time I have a chance to disassemble it to see if it’s made in Japan. OK, that’s it. It can still work normally after reassembly, which means it’s not broken. I’ll take some photos to commemorate the next time I repair something, in case of emergency (for example, to meet friends by disassembling it next time)

通宵敲代码

Isn't the radio-controlled clock synchronized with the radio transmitter? Why is it not keeping accurate time?

lyg2275

It doesn't receive signals 24 hours a day. It usually receives signals automatically at night and not during the day. It is accurate right after receiving the signals, but becomes inaccurate after walking for a while.