[Yaesu] Yaesu FT991 heat and power output

[John Geiger]

I have an early serial number Yaesu FT991 (2015 make) that I bought used
about a month ago.  So far I like the rig but have discovered something
about it that is a little unsettling.  The local ham I bought it from said
that it has been back to Yaesu for the final fix, but I know he didn't send
it back, and the original owner didn't send it back, so I don't know if it
has actually been repaired for that issue or not.  I have nothing to verify
that it has.

After the rig has been on for several hours, which means that it is getting
warmer than when I first turn it on, the power output seems to drop some,
maybe about 20 watts or so.  This seems to be a little more evident when
the internal tuner is in line also.  So far it is still putting out full
power when I turn it on, so I don't think it is the final transistor issue,
but I can't say that I have observed this on other rigs I have owned.

Have others seen this issue?  If so, is there a fix for it?  I do run it on
FT8 a lot, but there are also plenty of times it is sitting on received and
hasn't transmitted for a couple of hours, so that should cool it down from
any FT8 sessions.  The fan does come on during transmit so it is working.

Any help or insight would be appreciated.

73 John W5TD