[Icom] ICOM IC756 Pro II Problem

[Jim Frederick]

I have a problem with my 3-month old IC756 Pro II. It works fine up through
the 10M band in all respects. I tried to use it on 6 meters for the first
time and here is what it does: When the transmitter is keyed, even on SSB
with the power control and microphone gain both all the way down, it goes to
full power output on some frequency other than 6 meters, around 80 meters I
suspect. Obviously there should be no power output on SSB with no microphone
input. And it should not have full power output with the power control all
the way down.

Occasionally it will put out RF on 6 meters as long as the microphone gain
is near zero. With extremely light microphone input I can hear a normal SSB
signal on a second 6-meter receiver in the room. But as the modulation is
increased to anywhere near normal it "snaps" to full power output (power
control is still full counterclockwise!) and the signal in the other 6-meter
receiver disappears.

My 6-meter antenna is flat, fed with ALL Andrew 1/4 Superflex hardline and
7/8 inch LDF hardline from the jack on the ICOM to the flex section at the
rotor atop the tower. Problem also occurs when using a Bird dummy load.
Occasionally it seems like it is going to work correctly when using the
dummy load, but it will always "snap" to full power after a few seconds.

ICOM in an email response to me says it probably is RF feedback. I don't
think so, because there should be no RF at all in SSB with both the mic gain
and the power control all the way down.

Anyone ever heard of this problem? Any ideas? Thanks in advance,

Jim Frederick W4LF   jimfred@tampabay.rr.com