Mic not working at all.

Evening,

Just picked up an iPhone 4 cheap, needed some repairs doing. All works now bar mic, not in calls, face time or voice memos. Nothing.

Have replaced mic itself, the one that's part of the charging dock assembly?

Have tried all the tricks, needles, hoover etc etc. still nothing at all on anything. All cables inside the phone are on and correct.

Can any of you advise on what next?

Thanks