[time-nuts] strange hp 5345A option C19

[Luca Dal Passo]

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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