Bypass cap issues in the PA likely allowing the PA to break onto oscillation.
Bob, K4TAX
Sent from my iPhone
> On Oct 8, 2014, at 5:56 PM, Douglas via TenTec <tentec@contesting.com> wrote:
>
>
> One of my Omni D's (series C) has starting having a problem...
>
> It shows up first on CW - the final current will suddenly jump up and trip
> out the supply.
> It seems to do this only over a very narrow temperature range. Cold it's
> fine, with the final amp assembly warm, it's fine.
> As I back off of drive, the behavior returns to normal at around 60 watts. As
> I push drive toward 100 watts current will jump, especially on high speed CW
> "dits" from around 16 amps to over 20 and the supply will trip out. As the
> process is repeated a few times, perhaps due to the the final amp assembly
> warming up, and then all is fine, making it hard to troubleshoot.
>
> Using a second Omni D with the same power supply, antenna tuner and antenna
> and all is fine.
>
> Something in the final amp breaking down at a certain temperature range??
>
> Any thoughts?
>
> 73,
>
> Doug/WA1TUT
>
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