1. You may check the circuit surroundings first and see to it that it is free from dirt, foreign object and corrosion, a corroded components may also cause the problem, clean it first as necessary.
2. You may start to check the VSIM line paths continuity by using a multimeter, start from the VSIM capacitor through to the SIM card pin connector, to check if that said line is okay.
3. Check the ground line of the sim card pin connector, If the ground line is cut it also cause the problem.
After dis assembly check all sim jack points at mother board with meter.check all these parts and track that are given in above diagram and if any of them is missing apply jumpers to make that path in good condition.if any of the components is missing replace it with new.
Samsung S3 Mini I8190 Sim IC Solution Jumper Problem Ways Sim Not Working Sim Not Valid
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