Javier....Thanks so much for responding. On your advice, I opened X-Plane, clicked Plugins/Plugin Admin/Enable-Disable but all I could see were the two plugins I use-Checklister and Pilotview; no sign of Mentor [ panic ! ]. However I couldn't resist a quick circuit and before closing-down thought I'd check the plugins again. There it was!!! Mentor so I clicked a few times to get the green tick to enable, checked the radios and yes they now tune. So yes it was a bit fiddly [especially for someone as inept with computers as me] but problem solved. Once again Javier thank you for the acf. and for your backup and patience.