ICF-C120 SONY type FM/AM two band digital clock radio, using foreign standards for AC110V x 60Hz. Power consumption of 5W. Due to our use of city electric standard voltage AC220V, frequency 50 Hz and then, it should be first 26 feet of the machine in large scale integrated circuit LM8560 (50 / 60 Hz) choose to end with a wire and its 15 feet (VSS) to connect, to adapt to China's power supply frequency. And then a buck transformer (usually self coupling) will be used for 220V power down to 110V for the use of the machine.vQTservice manual download site
This machine has the advantages of small volume, machine can not accommodate the transformer, and in the machine with a transformer after all are cumbersome, not easy to use, so the electric air pressure method (see Figure 1), drop the city electric 110V for the machine with the country. The circuit for R discharge resistance, residual charge discharge capacitor is C. C should choose the high quality of the voltage of the 630V no polarity capacitor. The small size of R and C are mounted directly on the machine, compared with the transformer is more convenient and flexible. This machine power consumption is small, such power supply effect is good.vQTservice manual download site
The use of this machine has been part of the normal work of radio, but only a digital electronic clock display, no display timing figures. The machine timing digital display circuit according to the real plotted as shown in Figure 2. The principle is AC 50Hz signal from the transformer T, secondary (N2) removed the R106 buck c105 filtered and 25 feet added to the LM8560 for its internal 50 frequency divider circuit after get the standard second signal (timing standards), the cumulative time again through the internal decoding and driving circuit, from 1-13 feet output sum signal, for display display timing.vQTservice manual download site
From the failure phenomenon analysis, LM8560 and the display intact, the fault in the 50Hz AC input signal circuit. 25 feet check LM8560 R106 and c105 found R106 normal but c105 serious leakage and lead to AC 50Hz signal cannot be added to the LM8560 25 feet, make 1-13 foot stroke segment output signal, the display load time digital display. Because the colon is not affected by the signal display, it can display, after replacing the C105 troubleshooting.

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