FLY E185
Service Manual
CKT Confidential
Page 34 of 47
should diagnose the RX part first before TX.
4.1 Power on problem
About the power on problem, first, we should confirm the current of the handset, because the
current is very useful for us to analyze the failure. When we connect the handset to DC power
supply, we can clearly read the current of this handset. If the value is much bigger than the normal,
it means this handset must be short circuit (Baseband IC, ESD protection Diode, RF PA, etc.). If
the value is 0mA, it means power supply circuit problem, we can check this circuit step by step
until find out the defective component. If the value is smaller than the normal, it means software
or periphery circuit problem.
What’s more, you can measure the 12-route LDO voltage: VCORE1(0.9V~1.8V),
VCORE2(0.9V~1.8V), VM(1.8V/2.8V), VPA(1.3V~3.4V), VIO(2.8V), VBT(1.3V/1.5V/1.8V/
2.5V/2.8V/3.0V/3.3V), VCAMD(1.3V/1.5V/1.8V/2.5V/2.8V/3.0V/3.3V), VSIM(1.3V/1.5V/1.8V/
2.5V/2.8V/3.0V/3.3V), VWIFI2V8(2.5V/2.8V/3.0V/3.3V), VWIFI3V3(2.5V/2.8V/3.0V/3.3V),
VCAMA(1.5V/1.8V/2.5V/2.8V), VA(2.8V), VTCXO(2.8V), VRF(2.8V), V3GTX(2.5V/2.8V/
3.0V/3.3V), V3GRX(2.5V/2.8V/3.0V/3.3V), VGP(1.3V/1.5V/1.8V/2.5V/ 2.8V/3.0V/3.3V),
VSDIO(2.8V/3.0V), VUSB(3.3V), VRTC(1.2V/1.5V/2.8V), VGP2(1.3V/1.5V/1.8V/2.5V/2.8V/
3.0V/3.3V), VDIG(1.8V). Then measure whether the 26MHZ, 32KHZ output the CLK signal with
right frequency to baseband. If no fault occurs, continue to check FLASH, baseband chip by
download a code, if it can download DA, indicate baseband is normal, otherwise re-soldering the
baseband chip and memory or .replace these chips if all the steps can’t solve the fault.
In the last, no for all of these main chipset need to be check one by one, it depends on the faulty
phenomenon of this handset. Periphery circuit also very important for all of these problems, BTB
connector, I/O connector, USB connector, Battery connector also much problem, these
components are easy to check or replace. So when we faced the faulty handset, we need to follow
the easy circuit first, and then difficult.
Remark: Interrelated components are mainly as below: Baseband chipset (MT6268), MCP Flash
，
26MHZ VC TCXO, 32KHZ crystal.
