[TenTec] omni 6+/ power issue

[Wayne Dial]

My OMNI 6+ has a power issue on 20m and 17m, it drops to 50w output on 20m and 
15w on 17m. All other bands are okay.  I've checked the output of the L.O. Mixer 
board, port 26, across a 50 ohm load. 160m through 40m, the the output is 800 
mvpp and and drops to 100mv on 20m and up. I don't think it is the output 
filters of the PA  because 20m and 17m don't share the same filter. The L.O. 
Mixer is nested below another board so I can not make any measurements on that 
board other than ohm meter readings.  Has anyone seen this before?

Thanks, 
Wayne/w8aju