[time-nuts] Is a crystal likely to change frequency by 3% ?

GandalfG8 at aol.com GandalfG8 at aol.com
Mon Nov 26 15:17:00 UTC 2012


David
 
Try here, they have the service guide but no component level info  
available that I can see.....
 
_http://na.tm.agilent.com/8720/document.htm_ 
(http://na.tm.agilent.com/8720/document.htm) 
 
Regards
 
Nigel
 
GM8PZR
 
 
In a message dated 26/11/2012 14:12:55 GMT Standard Time,  
david.kirkby at onetel.net writes:

I've got  an HP 8720D VNA. This has been out of support from Agilent
for 8 years, so  its getting on a bit. There's a clock in the
instrument which keeps the  date and time. This is losing about 1 day
per month (rough guess), so it  has slowed by a bit over 3%.

I'm guessing this is likely to be a  battery running flat, but are
there any other likely causes? I know crystal  can jump in frequency,
but I'm guessing not by 3%, but perhaps if there was  stress in the
crystal, it might be.

It does not help the fact I  can't find a service manual for this
instrument. It's also a fairly  expensive bit of kit (I paid $16,000 a
few months back), so I'm not keen to  screw it up. If need be, I'll
write a bit of code which sets the clock from  my computer whenever the
GPIB is used. I've no need for precision time  keeping on this, but it
would be nice to have a copy of the date and time  on any printouts.
That's not possible when the clock runs so  slow.

On the off chance anyone does have a service manual for an  8720D,
please let me know. I'll buy a copy if need be. There is not one  on
the Agilent web site - only the user  manual.

Dave

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