[time-nuts] Difference between HP 5370A and 5370B

John Ackermann N8UR jra at febo.com
Sat Apr 16 11:43:01 EDT 2005

David Kirkby wrote:

> jim_johnson at agilent.com wrote:
>> Hi David,
>>    I will check with another guy tomorrow (the last
>> surviving technician), but one person "in the know" has this to say:
> I know know the S/N of this unit, although I don't have it yet. The 
> S/N of the 5370B is 2904A02491. If anyone is able to determine the 
> date (and/or part number) of the manual that will cover this S/N, I 
> would like to know.
> I gather there were some changes, over the years, so there is no point 
> me buying a manual that only covers up to version earlier than mine.
> It would also be useful to know if the manuals for later releases were 
> completely new manuals, or just had a few pages extra loose pages 
> slipped in. If the latter, could they could have fallen out of course, 
> so care is needed when buying a manual.

Hi David --

The first four digits of an HP serial number tell you the revision level 
-- the first two numbers plus 60 are the year (ie, 29 is 1989, quite 
late for a 5370), while the last two digits are either the week or a 
series number, I'm not sure which.  These digits only guarantee that 
your unit was built after that date, but they are a good guide to 
relative lateness.  HP manual changes are keyed to that four-digit 
series.  Usually, new manual editions come out fairly infrequently, and 
they include change pages showing all the series changes up to the 
version shown in the manual.  But in reality, the changes are generally 
pretty small and I usually don't worry much about matching up the series 
number unless I have serious repair work in front of me.  (Though note 
the recent discussion about the long time constant in the 5061A Cesium 
-- there are at least three manual versions available, and there are 
some significant difference in the manuals and the way the schematics 
are laid out -- but the 5061A was a big ticket item that was in 
production for a long time.)


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