[Yaesu] FT-990

[Tom Homewood]

A friend is having problems obtaining full power output on cw.  Listed
below are the things he has tried and a statement of condition.  Any one
have ideas on the source of the problem?  The friend is WA8SDA,
fmauser@juno.com.

Fan is OK......let me give you the results of testing I have done.
Problem seems to be only in cw mode and power starts to dwindle after 
45 minutes of being on and just in a receive mode. With the xmtr 
being keyed every 15 minutes for a check of output power(xmtr would 
only be on for a couple of seconds to read the meter.)  After  1 hour 
and 5 minutes output power has dropped to 5 watts out, and then slowly 
starts to rise to about 60-70 watts out after about 2 hours of on 
time.  It then stays at this 70 watts out or so unless I hold the key 
down for a few seconds and the power will drop to about 60 watts and 
remain there.  At any time during this testing if the ssb or fm mode 
is enabled, I will always have ~110 watts out, not so with cw.

Test conditions:

All testing into a Heathkit Cantenna
Results are the same on all bands, except I did not test WARC bands
Makes no difference if antenna tuner is in or out of line
RF power and mike gain set to max
Meter always shows 13.5 volts dc
Icc will diminish as power falls(only for cw, ssb and fm OK)
Fan will run initially in cw setting since it has good output, but as 
power drops fan doesn't come on......not really needed I guess.
Comments? Questions? Input? Appreciated.

Tom, W1TO




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