[time-nuts] HP 10811A failure

Azelio Boriani azelio.boriani at screen.it
Sat Oct 13 11:05:55 EDT 2012


And, why 12V for the oven? The 10811A manual states from 20V to 30V for the
oven. 12V for the oscillator itself.

On Sat, Oct 13, 2012 at 4:34 PM, Tom Knox <actast at hotmail.com> wrote:

>
> Sounds like another dead cap.
>
> Thomas Knox
>
>
>
> > Date: Sat, 13 Oct 2012 14:51:54 +0200
> > From: rfnuts at arcor.de
> > To: time-nuts at febo.com
> > Subject: [time-nuts]  HP 10811A failure
> >
> > Hi All,
> >
> > both of my double oven 10811A's have been running flawlessly until now
> > when I noticed that the output power has dropped by about 3 dB (measures
> > only 4...4.5 dBm at 50 Ohm load), and the noise floor has gone up by
> > about 20 dB, while the frequency is still spot on.
> >
> > I used them for various mesurements, so I can unfortunately not remember
> > what might have caused the failure. Only the 12V linear lab power supply
> > that fed the heaters had developed a completely dead filter cap, so the
> > feeding voltage was a 100 Hz sawtooth rather than DC. The heaters appear
> > to be still working though. I'm only using the internal heater. They
> > draw some 700 mA at power up and drop to around 150 mA  each when warm.
> > So the oscillators are unlikely to be cooked inside. Something must have
> > happened to the 10 MHz output, possibly an ESD issue?
> >
> > Before I start taking them apart, can anyone tell what has happened or
> > what to look for first?
> >
> > Regards,
> > Adrian
> >
> >
> >
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