Pete,
Thanks! I saw a reference today stating that these boards “in the oven” often
have solder joint problems, which makes me think that my be heat related, as
well.
I appreciate this additional information. I only have a 20 mhz scope, but I
know people! ;-)
Thanks again!!
Jim AF3Z
Jim Goudie — jagoudie@comcast.net
610 Kraybill Church Rd
Mount Joy, PA 17552
> On Jan 28, 2022, at 1:43 PM, Peter Bertini <radioconnection@gmail.com> wrote:
>
> *To*: tentec@contesting.com
> *Subject*: Re: [TenTec] Omni VI warbling sound
> *From*: Peter Bertini <radioconnection@gmail.com>
> *Reply-to*: Discussion of Ten-Tec Equipment <tentec@contesting.com>
> *Date*: Wed, 26 Dec 2018 09:15:59 -0500
> *List-post*: <mailto:tentec@contesting.com <tentec@contesting.com>>
>
> That warbling can also be caused by a HFO crystal that is trying to phase
> lock to the master oscillator. The PLL will sweep the oscillator loop
> voltage trying to achieve a locked condition.
>
> I've had problems with a few (three) of my Omni VI rigs developing problems
> with the oscillators on the 81595 LO Mixer Board. If the problem is not in
> your VFO PLL, look at the lock signal on Pin 11 of U13 on the CPU board.
> It should be a very narrow negative pulse (100 MHz scope, fastest scan
> rate) and stable. Oscillators are adjusted for minimal pulse width. If an
> oscillator is out of lock, you will see a lot of jitter on pin 11.
>
> If anyone who has found a cure for this issue I'd appreciate hearing from
> you. It appears to be heat related, as the crystals age the board becomes
> very heat sensitive, and the board is in encased in what is basically an
> oven which adds to the problem.
>
> Pete
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