The Spey engined Phantom ramps were definitely programmed, if I remember rightly to a schedule dependent on total air temperature. I can remember investigating several ramp servo valve failures. The cap head screws that held the covers over the end of the spool valves used to fail, probably because of pressure fluctuations in the hydraulic system, or it may have been a batch of duff screws, my memory fails me on that.
In the early days there were lots of hydraulic pipe failures which we investigated at HOSM. Initially we did it by calibrated feel by hand during during ground runs. Later using pressure transducers and accelerometers we found the pipes were vibrating in tune with a pressure ripple from the engine driven pumps. This was as a result of McDonnell Douglas changing the length of the hoses between the engine mounted pumps and the airframe, as a consequence of fitting the Spey in place of the J79. We fitted a small spherical capacity absorber in the end of the affected pressure hoses and it significantly reduced the amplitude of the pressure ripple and the pipe failure rate.
I remember a story, possibly apocryphal that on one of the Phantom bases the engineering officer got fed up of repeated pipe failures and was convinced his riggers did not know how to make and fit hydraulic pipes. He therefore gave them a demonstration and made and fitted a pipe himself. It failed on the next flight.
Walbut