After observation, black screen, the menu, characters, operation keys are normal. MMmservice manual download site
 MMmservice manual download site
Check TDA8843 18 feet 5.6 V when the voltage is normal, not normal 4 V, 18 feet circuit, disconnect for 4 V TDA8843 starts for the black screen, silent. Check TDA6108 5 foot 6 V, but in only 4.5 V when the phone is switched on, wait for a period of time up to 6 V, TDA8843 start, have a sound figure. Disconnect TDA6108 5 feet, boot for the black screen, not for a long time to boot is black screen for a few hours. Connected to TDA6108 5 feet right away a figure sound, then disconnect TDA6108 figure 5 feet also normal. That means TDA6108 5 feet on when to start the TDA8843 for 6 V voltage, but the boot TDA6108 only 4.5 V, 5 feet TDA8843 cannot start, so went black. In TDA6108 boot properly. Please pay attention to while maintenance TDA8843 18 feet above voltage to 4.5 V, TDA8843 internal will work. Otherwise, black screen, silent.MMmservice manual download site