Some users have reported that the ALC meter indication occasionally jumps during long key down periods on the 28 MHz portion of the bands. The symptom may be caused by the ground foil of the Final unit (X56-1430-00) coming in contact with one or more of the projections on the final heat sink, due to expansion when the temperature rises.
Apply Mylar insulating tape to the projections on the heat sink, to prevent reoccurrence of this symptom. See figure below.
Notes: This bulletin is applicable to units prior to serial number 3080001.
Time required for this modification is ½ hour or less.