Symptom: Complete and total loss of receiver sensitivity.
Repair: The identified fault was oxidation of the DX switching relay contacts, which are located on the RX NB Unit. After applying a small amount of contact cleaner to the relay contacts using a strip of paper, the radio receiver has regained full sensitivity, including the on-board low-noise pre-amplifier.
1 DX switching relay contacts cleaned with a strip of gloss paper
and contact cleaner.