On Jan 17, 2011, at 5:17 PM, Dr. Gerald N. Johnson wrote:
> On 1/17/2011 3:10 PM, Jim Goudie wrote:
>> Hello all,
>> A tale of misfortune and fortune. And before I decide which way to go, I
>> thought I'd check and see if the symptoms ring any bells out there...
>> I was on the air with my Omni VI opt 3... I was switching bands fairly
>> often, and the last switch was to 160. I set the tuner, which for 160
>> produced a rather sharp null. When I keyed the rig, the breaker tripped.
>> That's odd, I thought. I hadn't tripped the breaker like that in many, many
>> Shortening the story, after resetting the breaker, I found it would trip as
>> soon as the output power got up over a watt or two.... And it did it on 80
>> meters... and 20 meters without the tuner in line. I shut down for the
>> night. Today, going into a dummy load, it put out power until about 50
>> watts out, and then the needle on the power meter went erratic, but the
>> breaker never tripped.
>> The side story& symptom are that last night, after fooling around, I
>> realized the rig wasn't receiving any signals. This morning, when I first
>> turned it on, it received ok. But, after doing my dummy load testing, the
>> received signals were gone again.
>> So... I pulled my trusty 544 off the shelf to replace the Omni VI at my
>> operating position... and operated for three hours with that.
>> I'm guessing the problem lies in the SWR-sensing, tx-rx switching stuff in
>> the output... I haven't cracked it open or even looked at the schematic
>> yet... Any thoughts?
> I think that's the first place to look but be sure all the board grounds
> are tight so that the PA or RF board isn't oscillation at some out of
> band frequency.
> I recall losing the diodes in the SWR sensing/ALC detect area has made
> several TT radios do weird thiings.
> 73, Jerry, K0CQ
>> Jim, AF3Z
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