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General telephone circuits by the ringing system, polarity conversion system, dialing and call systems. New phone hands-free telephone system, LCD displays of high frequency circuit system and cordless telephone system. Typically, repairing telephone method is a headache medicine head, foot pain foot, and in fact, each part of the circuit are connected to each other, such as calling some components of the circuit is not normal Act of dialing for a dial-up system exception. As was the case in this example.Npnservice manual download site
Npnservice manual download site
Fault inspection of the focus in the Pulse Dialing circuit because the supply voltage has not yet been added to the dialer and call circuit. Related circuit as shown in Fig. Measuring the protection resistors R6, transistor V1 damage is found. After the replacement, the function of pulse dialing, but not dual-tone dialing. DTMF dialing and dial measuring IC W91320 {13} PIN to 0V, normal, {12} feet almost 2V voltage, R34 resistance to normal. Try changing C19, W91320, and 3.58MHz crystal oscillator, fault remains. Therefore, suspects that the machine is a system fault call. Measuring TEA1062 ¢Ù feet (LN) voltage of only 4V,{13} feet (VDD side) of 2.5V. Welding open Zener diode ZD2, the voltage does not change, then unsolder TEA1062 ¢Ù feet, rising {13} pin voltage 4V, TEA1062 internal damage is suspected. Try replace with new parts, dial-up properly, sent by normal troubleshooting.Npnservice manual download site
TEA1062 is produced by Philips phone private calls IC, ¢Ù feet for line voltage input, the maximum operating voltage of 12V, minimum operating voltage of 4V;{13 positive power supply decoupling for line-end} feet, which not only provides integrated circuit power supply pin voltage back electret transmitter power supply. If the PIN voltage is too low, both parts of the circuit were not working properly. Under normal circumstances, TEA1062 ¢Ù feet minimum voltage is 5V, and if it is below this value, and the external circuit, and then integrated circuit is damaged. This case is for IC part damaged, affecting DTMF dialing, and sent to the voice volume down.
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