[time-nuts] Bad batch of HP10811's

[Jeroen Bastemeijer]

Dear Rick,

Are you sure the 500Hz is too much for a cold oven? I checked my 5345A 
(recently acquired) counter, which was switched off for some time. 
Measuring the frequency directly after applying power and switching on, 
resulted in about 1640 Hz frequency offset. After warm up, the error is 
below 0.4 Hz. (The unit used here is a 10811a). The error drops pretty 
fast, allthough I didn't measure an accurate curve. Is the frequency 
difference caused by the tempco of the oscillator circuit?

Cheers, 73s Jeroen PE1RGE

Rick Karlquist wrote:

>I'll apolgize on behalf of HP for putting in that stupid thermal
>fuse.  It cannot be soldered in for the obvious reason that the
>soldering temperature exceeds the fusing temperature.  Therefore,
>it must be socketed.  It does NOT have gold plated leads, and
>hence the reliability of the contact with the socket is poor.
>I think the reason for it was that if the oven ran away, the
>thermal foam would burn up and out-gas toxic fumes.  Ovens very
>rarely run away.
>
>The unit that is 500 Hz off is not due to a cold oven.  There isn't
>that much tempco in the crystal.
>
>Rick Karlquist N6RK
>
>
>John Miles wrote:
>  
>
>>That's almost always caused by the thermal fuse on the outer PCB.  They
>>tend
>>to open up due to aging.   Just short it out... it was a ridiculous place
>>to
>>put a thermal fuse anyway.
>>
>>-- john, KE5FX
>>
>>-----Original Message-----
>>From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
>>Behalf Of Jack Hudler
>>Sent: Sunday, January 14, 2007 12:00 PM
>>To: 'Discussion of precise time and frequency measurement'
>>Subject: Re: [time-nuts] Bad batch of HP10811's
>>
>>
>>
>>Who sold them?
>>-----Original Message-----
>>From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>>Behalf
>>Of Mark Amos
>>Sent: Sunday, January 14, 2007 1:41 PM
>>To: time-nuts at febo.com
>>Subject: [time-nuts] Bad batch of HP10811's
>>
>>Time-nuts,
>>
>>Seems like a bad batch of HP10811's was dumped on e-bay over the
>>holidays...
>>Some (at least
>>2) won't tune up to 10MHz: one won't adjust above 9,999,530 and the other
>>peaks
>>around
>>9,999,920 after warming up for a day or so.  It seems to stay on frequency
>>(albeit the wrong
>>one...)
>>
>>I did some preliminary checks (internal reference voltages, OK, etc.)  I'm
>>thinking that it
>>must be a bad crystal to be this far off.
>>
>>C'est une cause perdue? (I.e. did I buy a "parts" unit?)
>>
>>Mark
>>
>>
>>
>>
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>>    
>>
>
>
>
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-- 
Ing. Jeroen Bastemeijer

Delft University of Technology
Department of Electrical Engineering
Electronic Instrumentation Laboratory
Mekelweg 4, Room 13.090
2628 CD Delft
The Netherlands

Phone: +31.15.27.86542
Fax: +31.15.27.85755
E-mail: J.Bastemeijer at TUDelft.nl