[time-nuts] HP 10811A failure

[Tom Knox]

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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