[TenTec] OMNI VI+ Problem

[Robert Weingaertner]

I had a similar problem on one band with my Corsair I. I think that the 
problem turned out to be an open or wrong value capacitor in the 
final low pass filter. If the match were perfect, it would trip out, but
if the load was slightly detuned for a higher SWR, it would be OK.
The low pass filter was just not providing the correct impedance match
for the final. I did not have tha capability to test the capacitors, 
so I got a replacement board from TT and sent the original board
back under warranty. 

    73, Bob WB2VUF


Jimmy D. Roller wrote:
> 
> Has anyone encountered this problem before? My 7 year old OMNI VI+
> (option 1) has developed a problem with drawing excessive current on 15
> meters. All other bands behave normally, but on 15 meters, I can only
> show 80-85 watts output before the power supply over-current circuit
> trips. This OMNI has always been a bit "touchy" on 15 meters into
> anything less than a near perfect match, but I have always been able to
> put out 100 watts into a good match. The problem started during the NAQP
> CW contest which is not a good time, what with jumping around the bands
> snagging multipliers. Since then I have done a few tests on the gear.
> First, I insured that "all" my SWR bridges were at least close to one
> another. The 238 tuner provides a > 1.2 SWR on any of the antennas
> tried. In addition, it makes the Hercules II very happy on any of the
> antennas. Next I hooked up a dummy load and got the same results. I even
> verified the SWR of the dummy load with the Autek RF analyst. Still the
> problem persists. I have tried various length coax patch cables between
> the boxes. The dummy load was connected direct to the OMNI VI
> with an 18 inch piece of RG-213.
> 
> I use a TT 960 power supply that has been modified to a 961 by turning
> the filter cap upside down per TT Service Dept. It has been around the
> shack for 11 years and is still in good shape. The last thing that
> happened to the OMNI before the problem presented itself was the Lock
> Pulse alignment using TT's procedure and commercial grade scope and
> counter (I have a friend who maintains all county radio/electronic
> gear). That's about it. The rig performs as expected on all other bands
> into a dummy load or antennas and/or antennas matched with the 238
> tuner. 15 meters is the only place the problem exists.
> 
> Has anyone encountered this problem before? I would appreciate your
> sharing any experiences you may have had. Perhaps the over-current
> protection circuit is a bit on the stingy side and the OMNI VI needs a
> bit more current to achieve full output on 15 meters? I dunno. I thought
> I would first plumb the accumulated knowledge and wisdom of the
> reflector before I once again call the wizards just down the road. Any
> comments or suggestions will be much appreciated. Thanks in advance.
> 
> 73/CUL,
> 
> Jim, N4IR
> 
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