[R-390] 16 KHz filter oscillates

[rbethman]

Roger,

I would go with the ONE suggestion regarding grounds.

I would believe that this would be the highest probability.

You know enough about the capacitors.  Unless you have some freak 
failure in ONE that bypasses.

Best of luck!

And thanks for your very in-depth knowledge that you have shared!

Bob - N0DGN

On 4/3/2011 9:33 PM, Flowertime01 at wmconnect.com wrote:
> Fellows,
>
> I have a R390/A on the bench. As I peak up the 16 KHz mechanical filter it
> goes into oscillation. I get a nice audio tone out of the headphones. I can
> change that tone with adjustment and drive it beyond the audio range. The
> oscillation continues as it can be metered on the diode load. I can peak the
> level with the trimmer caps. I can back the trimmers back off the oscillation
> point and get a signal through the filter at almost the same level as the
> other filters. I do not know if the filter will ring at these trimmer
> settings with real world signals.
>
> Is there a cure other than replacement? Will replacement cure the problem?
>
> The deck is late production but still with the black beauties. The only
> change was to get the orange drop in before power was ever applied.
>
> Is there a wire dress layout problem that leads to this problem?
>
> Thanks
>
> Roger AI4NI</HTML>