Paul...if you operate key down into a dummy load on those frequencies does
the rig still exhibit those symptoms?
Try that and sniff the top of the Omni near the heat sink (sounds odd, I
know).
If there is any smell like a burned resistor I may have a solution for you
that requires a lot of disassembly and a little grinding of the pc board.
My output transformer arced over between the 2 output transistors causing
the phenolic (or is is fibreglass?) PC board material to char black and
become conductive. I ended up grinding away the PC board and creating an
air gap between the to solder pads of the transformer...fixed my problem.
My symptoms included burnt resistor smell, flickering of ALC at key down
and distortion of audio on transmit. But yours sounds so frequency specific
that I doubt it's the same problem...like I said...just a shot in the dark
in case you try everything else with no success.
Tom K2TA
Greenwood Lake, NY
----- Original Message -----
From: "Paul" <gw7lhi@hotmail.com>
To: "Ten-Tec List" <tentec@contesting.com>
Sent: Saturday, September 13, 2003 5:29 PM
Subject: [TenTec] Help - Omni V PA
Hi.
I have an OMNI V that I'm very happy with, apart from a minor issue on 20m.
I've noticed that on 20m above 14.250, the PA appears to go unstable /
parasitic.
This results in poor audio reports from some contacts.
I've tested into a dummy load, and in tune mode as I vary the carrier power
I notice a definite point where the PA ( or whatever ) suddenly starts to
misbehave.
This is visible on the ALC indicator, which dims slightly or begins to
flicker even though the indicated RF output is not changing according to the
external metering / dummy load.
The current drawn does not change significantly when this happens, it stays
right around 19 amps at 100w out.
The effect is much more noticeable with an antenna connected.
The antenna has a SWR of 1.2:1 and does not cause any problem to my FT-102
or other solid state PA rigs.
Any ideas?
The problem only occurs on 20m between 14.250 approx and 14.350.
The only clue I can offer is that the RF output is a little lower on 20m
than any other band, but only by about 3-5 watts.
The PSU is a home brew 30 amp hernia inducing beast, there is no issue with
it as the same effect is present with a fully charged car battery.
I have also wired the DC power cable directly into the radio, as the molex
(?) connector was causing approx 0.5v drop through it.
I have also bypassed the fuse holder, no difference.
Thanks for any input!
Paul MW0CDO South Wales.
PS: Does anyone know where I could get a set of keypad buttons suitable for
the V.9 upgrade?
They appear to be like rocking horse fertiliser here in the UK...
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