The battle continues. After my previous post there was no sign of life in the servo. In addition it was possible to turn the servo by hand, this should not have been the case if the PWM signal was active. Another look at pins.h and Configuration.h showed the following anomaly:

Configuration.h line 65
#define MOTHERBOARD 80
this is for the Rumba board

but in pins.h the only place where the servos are referenced starts at line 454:
#ifdef NUM_SERVOS
and continues to line 468

This is part of the if statement at line 301
#if MOTHERBOARD == 3 || MOTHERBOARD == 33 || MOTHERBOARD == 34 || MOTHERBOARD == 35 || MOTHERBOARD == 77
which caters only for the RAMPS / MEGA RAMPS / 3Drag Controller boards.

I copied the contents of lines 454 through 468 in pins.h and inserted them at line 1251 which is the Motherboard 80 section.

A quick recompile and the servo now obeys instructions.

Any one see any problems with this modification?