Problem solved!
After removing the grub screw in the base I extracted the complete element.
Checked capacitors and soldered joints - all OK. Cleaned mild tarnish off
all element sections and matching sections. Took apart joints where grub
screws are fitted and cleaned mating surfaces. All the grub screws were
tight so had not worked loose. Also cleaned mating surface between feed and
aradial/mount boss. Reassembled and re-erected. Now working fine.
Seems probable that there can be come minor corrosion in joints with grub
screws and og the element itself. A good clean up every two or three years
would be a good move to prevent losses creeping in.
73 de Richard (Dick) G4BBH