Mic connector not functioning on MCS200 II control head

[Johnno]

Has anybody experienced this or similar condition before?
Appears that the fault possibly lies in the RJ45 connector on the control head.
Control head behaves as normal under all other operations.
When PTT is pressed, no TX!
I have tried different mics to no avail.
Then replaced type II with a GM1200E (similar to type III head), original tested mic was working fine.
Unfortunately I am unable to read this unit as it was programmed with CPS later than the one I use, so even with the type III head on it I can't load a new codeplug to enable operation of the new head.
I read somewhere on the board ages ago (maybe 2-3 years) about a component that was known to go U/S on these heads, but can't seem to find any posts that relate to it.
Any suggestion will be appreciated