RR Sport HSE TDV8
Car had not been started for a long time battery was flat.
Jumped from another battery and it started.
Drove home stopped battery dead. Put start charger on it spun over and started.
New battery fitted. Two days gone flat.
Fault message alternator field winding down to earth.

Fitted new alternator. Starts and runs fine battery does not go flat even after a week still perfect.

Clear the fault and after 30 seconds it returns.

I think using a high amp start charger knackered the first alternator but what else can it do as I cannot get rid of the field winding down to earth fault. I think I read somewhere about a diode pack (not on the alternator) that can blow as well.
Any pointers would be appreciated.

Cheers
Sid