1.before search the marking code (smd code),check the device on hand first,to see what is used
for,and is which grade,original of country?
For example,if the device's design country is Japan,then maybe 90% component on the board are from Japan supplier.when check the IC marking (smd code),we need to pay more attention to Japan manufacturer.
If the main design purpose of the device is cost down,then maybe 80% component on the board are from China supplier.when check the IC marking (smd code) need to pay more attention to China manufacturer.
below is the sample:Ricoh BJ-6 charger
This device's country of original is Japan,the main component are MIP2D2,M61032FP and so on,they are Japan manufacturer's product.
If want to search the smd component's IC marking (smd code),need to think about Japan manufacturer firstly.
2.Identify the smd component'spackage and IC marking
search target is the Diode (D21),as the picture below,IC marking (smd code)=J4 65
IC marking(smd code) J4 and 65 ，usualy one of them is marking code,the other one is date code.
3. If have vernier calipers,measure the size to identify the package.
size 4.38 mm x 2.66 mm
4.Search J4 on this website: www.marking-codes.com