[time-nuts] Totally unrelated, but..

Clint Jay cjaysharp at gmail.com
Wed Dec 7 15:16:29 EST 2016


I was looking for a low noise regulator to power a log amp/detector earlier
this year and was rather surprised to find the 78xx regulators were
considerably better than many of the "low noise" devices.

But!!

I've also had odd experiences with some brands of 78xx devices (and way
before the 'net was anything more than SLIP dial up to a shell so I doubt
they were Chinese fakes) ,  one was bad enough that it gave some very
random voltage measurements on a digital meter,  turned out of the was
creating all sorts of RF hash in the low VHF range up to and possible
beyond the FM broadcast band.

On 7 Dec 2016 20:10, "Joe Leikhim" <jleikhim at leikhim.com> wrote:

> Could the low noise parts actually be counterfeit, relabeled as such?
>
> Is the circuit the regulator feeds sensitive to a narrow band of voltage
> that the "good regulator" is outside of?
>
> Try replacing the regulator with a battery supply and resistor divider to
> attain the working voltage. Move the voltage around. A good potentiometer
> and stiff filter capacitors are recommended so as not to introduce "pot
> noise".
>
> Is something corrupting your test procedure?  I had a circuit that
> misbehaved due to floating logic pins reacting to static electricity on the
> work bench. Another time a diode was photosensitive.
>
>
>
> --
> Joe Leikhim
>
>
> Leikhim and Associates
>
> Communications Consultants
>
> Oviedo, Florida
>
> JLeikhim at Leikhim.com
>
> 407-982-0446
>
> WWW.LEIKHIM.COM
>
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