Loss of access to access to relevant information found spare battery bt400 external components for the filter capacitor c408, and then all the way through to the 0 ohm r420 power management IC u501 of j3 foot , the other way to the main screen chip select electronic switch v403 was measured . : required voltage 2.6v or so, current <= 4ma normal clock circuit , so that when repairs are usually the fault plane , first test bt400 whether the absence of voltage 2.6 ~ 3.0v , then remove bt400, check if poor ;. bt400 in fine , the power supply can be adjusted to 3v output , and placed in series with a multimeter 50 microamps file backup plus 3v voltage on the PCB - battery place, observe the meter pointer is greater than 4 microamps ; If more than four micro- Ann and put the pointer without instability phenomenon , then remove the v403, v503, check whether leakage ( available exclusion ) , leakage and replace through the above steps , the problem can be solved.