[TenTec] Omni VI warbling sound
dukeshifi at comcast.net
Wed Dec 26 12:31:53 EST 2018
Is the warbling present on all bands once it commences?
> On Dec 26, 2018, at 8:15 AM, Peter Bertini <radioconnection at gmail.com> wrote:
> 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.
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