[time-nuts] HP 10811A failure

Tom Knox actast at hotmail.com
Sat Oct 13 15:53:41 UTC 2012


I am sorry I assumed you had resolved your PS issues, I should have been clearer, I meant bad cap in the oscillator. I would temporarily solder a number of leads internally and check the different voltages for noise. Good luck on the repair.

Thomas Knox

> Date: Sat, 13 Oct 2012 17:30:27 +0200
> From: rfnuts at arcor.de
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] HP 10811A failure
> 
> At least not a power supply cap. No change on a different PS. Do you 
> mean the oscillator output coupling cap?
> 
> 12V for the oven because inside the outer oven lives a 10811-60158 ( see 
> http://www.realhamradio.com/GPS-oven-journey.htm ) that, as by the specs 
> sheet, is specified 12 to 30 V DC, 11 W max. at turn on (mine draws some 
> 9 W), and Steady state power drops to approximately 2 W at 25°C in still 
> air at 20 V (mine draws some 1.9 W at 12 V without powering the outer oven).
> 
> Adrian
> 
> 
> Azelio Boriani schrieb:
> > 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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> 
> 
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