On Thu, 20 Aug 2009 11:56:33 -0400, Wayne.B
wrote:

I've had an Icom 802 SSB with AT140 tuner installed on the boat for
over 4 years now. It uses the more or less standard 23 ft whip
antenna and has the same ground system that the old SSB had which is
alleged to be a copper strap running down to the bonding system. It
has worked fairly well up until recently but now seems to be
transmitting weakly and the control panel is indicating a high SWR.
Nothing has changed as far as I can determine and all connections seem
to be tight and corrosion free. I'm suspecting that the tuner is not
working properly but other than buying and installing a new AT140, I
can't think of any way to trouble shoot this issue.

Any suggestions?

Followup:

After trying all of the helpful suggestions here, and talking to a
number of people, the SSB was still not transmitting. Apparently
there are no longer any SSB tech guys in this area and bringing
someone over from Ft Lauderdale was going to cost a bundle. Gary
Jensen at Dockside Radio in Punta Gorda suggested buying a dummy load
and a Wattmeter/SWR Bridge to test definitively whether or not the
transmitter was working. That seemed like a reasonable suggestion
since MFJ Electronics has a good selection at reasonable prices.
Everything arrived today and I hooked up the wattmeter and dummy load
just before the antenna tuner, started a calling sequence with Winlink
and checked the meter. Everything looked good with over 100 watts
showing and the dummy load was heating up. It looked like it must be
a tuner problem since I'd already checked the antenna and ground as
best I could. To make a long story short I removed the test
equipment, hooked everything back up the way it was, and tried yet
another test transmission. This time everything worked OK and I was
able to contact several different Winlink gateways and check into The
Maritime Mobile Net. Apparently there had either been a bad
connection at the point where I inserted the wattmeter, or the
presence of all that official looking test equipment scared the radio
into performing properly. It looks like I'll need to carry the test
gear around when we go cruising from now on. Both the meter and
dummy load are good up to 200 MHz so they can also be used to test the
VHF radios if need be.