It is almost impossible to do a chip replacement. At least I haven&#39;t heard anyone who has done it.<div><br></div><div>Have you tried downgrading to a lower unlockable Baseband via Cydia?</div><div><br></div><div>When was your iPhone 3GS manufactured? I fit was after 2010 and you tried to upgrade to iPad Baseband 06.15.00, you may have bricked you iPad. </div>

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