Usually the symptoms you describe are caused by the transmitter's going into
oscillation causing runaway current in the finals. You can easily test as
follows:
a. With drive fully down, put the transmitter in Tune.
b. Slowly increase the drive, watching about any meter (RF, current, SWR,
etc.)
c. If when you begin to get a slight reading, the supply shuts down, you
have found the trouble.
The cure for this trouble is to replace the diodes in the circuit that
generates the ALC voltage. On whatever board they are are also two or three
other diodes. You ought change them all whilst you're in there. It is not
a hard job.
73, Mike N4NT
----- Original Message -----
From: "Virginia Smith" <ginnieruth@hotmail.com>
To: <tentec@contesting.com>
Sent: Thursday, January 14, 2010 01:16 PM
Subject: [TenTec] Please help with touchy OMNI - D
Hi All,
I've had this OMNI - D since 1998, bought from the original owner who had
had it serviced prior to sale, however all the time I've had it, the rig
has been very "touchy" The circuit breaker on the 252M power supply trips
often. I was told by a couple of local TenTec users to consult this list,
and that it could be an issue with the power supply or the ALC circuitry -
which I have never quite understood how to set.
FYI, I am on an 88 ft doublet antenna, fed with ladder line on an MFJ
antenna tuner. I can tune at low power, but when I go above a few watts I
am operating on the edge of shutdown. There is no evidence of stray RF,
as I get reports of a clean signal when I do get on the air.
Also I am currently using the same antenna/tuner setup on a loner Icom
rig, and everything is fine.
Any ideas?
Thanks
73
Virginia
KD5EZN
ginnieruth@hotmail.com
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