Here will introduce a new kind of mini portable phone

 Here will introduce a new kind of mini portable phone
Another IF IC and crystal, IF IC after power internal oscillator circuit for crystal start-up, by the IF amplifier output, 13MHZ clock usually after capacitors, resistors, or amplifier supply the CPU; also supply RF phase-locked loop circuit as the basic clock signal. Normal reset signal, the CPU just for the power, the internal registers in a random state, does not run the program, the CPU must reset signal to reset. The reset terminal of the CPU in the phone are generally low reset after a certain clock cycle, CPU internal register is cleared, then the voltage up again here is high, allowing the CPU to start from scratch to run the program. 13MHZ clock circuit failure. The CPU is not working properly. Version of the register is not working properly. In the actual maintenance, power IC, CPU version register Weld 13MHZ (or 26MHZ, 19.5MHZ) crystal, VCO non-working power the majority. There have appeared many kinds of phone in the market.The customers uses this kind of mini portable phone
About 20 ~ 50MA current stops moving or slowly the whereabouts of about 20 ~ 50MA current, but it stops moving or slowly the whereabouts of this description of the problem, the software self-test, but off. The current instructions, the hardware is already working, but the current is small, the memory short circuit or software does not work properly. Find the following: CPU memory Weld or damage; processing method: First, by using the blowing welding logic circuit, the second is the normal version with information (font) or the chip to be replaced, three in software maintenance instrument maintenance. There are about 100 to 150MA current, but soon fall; this phenomenon in the performance of the fault does not boot up to.
First, the mobile power supply circuit failure, the phone "reluctance" to meet the conditions of boot, but will shut down after the boot for a while. Mobile phone with a boost circuit is more prone to this failure. We know that the phone's battery voltage is low, typically around 3.6V, some phone's battery voltage is lower, the phone's circuit but requires a higher voltage, some mobile phones are set to boost circuit. When the step-up circuit failure and boost circuit switch on the phone machine influential, it is possible to cause the fault of the phone is switched on and then automatically shut down. Then phone can work well again for another 12 hours.
Heavy welding or substitution of normal chip can not boot, and use free to disassemble, repair instrument reading and writing can not should be measured individually to the peripheral circuits and substitution of these chips. The software is not caused by normal boot. Mobile phones during the boot process, if the software through, but will not boot, the software error is the main memory data is not normal, when the line is no obvious disconnection, the first substitution of the normal chip version or rewriting the software, and some chips The circuit will be damaged, can not be overridden.