[time-nuts] strange hp 5345A option C19

[GandalfG8 at aol.com]

Hi Luca
 
The earlier 5345As were fitted with the 10544A oscillator, I've seen units  
with both that and the later 10811, so it could indeed be the original  
oscillator.
If your 10544A has the PCB edge connector and  is installed in the usual 
place then without seeing what's actually been  done I'm a bit lost as to why 
it would have been modified. If there was a  problem perhaps with the 
original int/ext reference switching, or with the phose  locking to an external 
source, that might be a reason, but for that it sounds  like quite a drastic 
fix:-)
 
Regards
 
Nigel
GM8PZR
 
 
In a message dated 22/08/2013 10:31:06 GMT Daylight Time, iw2lje at gmail.com  
writes:

Thank  you Nigel for your comment.
Now I understand the reason why it may be  useful to have this
additional external link.
In the counter is fitted  an oscillator model 10544A (instead of a more
known 10811), but I  think  that it is the original one because the
date code of the serial  number is a bit old (year 1981). At that date,
the 10544 was still in use.  Observing carefully the way  in which the
internal connections to the  Ref In and Out are made, I notice that
wires, insulating material and  sockets are different from the original
HP's. So it seems actually to be a  user made modification not related
to option C19.
Good  bye
Luca




2013/8/21   <GandalfG8 at aol.com>:
> Hi Luca
>
> There are other  items of HP equipment fitted with Ref Out  and Ref In
> terminals  joined by an external link, with the intention that  the link 
is
>  removed to connect an external standard to the Ref In terminal,  but in 
a  "normal"
> 5345A the external reference is used to phase  lock the  internal 
oscillator
> which means that the unit can't work from an   external reference if the
> internal 10MHz oscillator has been   removed.
>
> However, I found some time ago that it is possible,  just by fitting a
> single link internally, to drive the counter via an  external reference 
even if
> the internal standard has been removed so  I'm guessing that the internal
> standard on this one might have been  removed at some time and a previous
> owner has fitted a non original  internal standard with a similar 
provision  to
> bypass the normal  arrangement.
>
> It should be fairly easy to check just by looking  to see if the  original
> HP oscillator is still fitted or whether  a different one has been  added.
>
> Whether or not this  relates to the Option C19 I don't know.
>
>  Regards
>
> Nigel
> GM8PZR
>
>
> In a  message dated 21/08/2013 17:00:21 GMT Daylight Time, 
iw2lje at gmail.com
>  writes:
>
> Dear  all,
>
> I have bought an HP  5345A. It’s ok and I’m  very glad. On the rear
> panel it is wrote  "OPTION C19" (a little bit  strange!) and there are
> two  additional BNC installed on the little panel  normally used to
>  place the HPIB connector when present.
>
> These 2 BNCs  are  named REF OUT and REF IN and there is a jumper cable
> that connects  the  output to the input.
>
> It seems to be a modification  made by some user  (very strange: I can’t
> understand why to place  an extra auxiliary bypass  for the 10 MHz
>  reference).
>
> Do you have an idea about this strange   modification and about the
> strange option C19? Could it be a custom  option?  Could the option C19
> and the 2 BNC for the reference  be  related?
>
> Thanks
>
> Bye
>
>  Luca – IW2LJE – Milano –  Italy
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