[ICOM] Mosfet Final Board 756 Pro3 Damage

[JK]

My756 Pro3 recently dropped in output on most bands by about 20%. On 160 
pwer out is 22 watts max. The PA board is the later version that now 
uses MOSFET finals.


Upon examining the PA board I found three 4.7 ohm chip resistors R38, 
R39 & R40 burned, cracked, broken completely. The solder holding these 
three chips became so hot. the solder melted and the broken resistors 
floated out of their correct positions.


This happened 3 years ago on the same radio. But then, in addition to  R 
38, R 39 & R 40, 4 final transistor had also shorted the Gate to 
Ground. 


As I get about 80% of power out on some bands, I think the finals are 
still ok. I have no idea what could cause R 38, R 39 & R 40 to burn up. 
They are in parallel with inductor 8 so I would think most current 
should pass thru 8 not these resistors.


Anyone else have a similar situation or any idea why these 3 resistors 
burn up?


Thanks all.


Jay...NE2Q