[1000mp] 1000mp Digest, Vol 57, Issue 7

[WB4U]

I ran into a similar problem some years ago with a friends FT-990. Problem 
turned out to be on the DC board. Seems the heavy wires were too big to 
solder directly to the board so Yaesu has crimped the wires into connector 
which then was rolled down to a size that would fit the holes in the PC 
board. Over time and crimp connection oxidized and would cause the radio to 
do exactly as you described. The fix for that radio was to remove the wires 
from the crimps, tin them, enlarge the holes on the PC board and solder them 
directly to the PC board. The radio is now working without a hitch for the 
last 5 years. The relays in the 990 were used only to switch between the 
built in and/or an external supply. The faulty wires were going from the DC 
board to the radio so it didn't matter which supply was in use, it had the 
same problem.

Johnny