[time-nuts] HP 10811A failure

Adrian rfnuts at arcor.de
Sat Oct 13 12:51:54 UTC 2012


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





More information about the time-nuts mailing list