[time-nuts] strange hp 5345A option C19

[Luca Dal Passo]

Hi Nigel,
     You are right.
A previous user, made a very very bad fix!!!!
There are some traks modified in the PLL board related to the external
reference.
Now I have to start with a complete restoration process.
I have dismounted the counter and extracted the boards. Fortunately
no other horrible items appeared.
Thank you again.
Regards
Luca




Il giorno giovedì 22 agosto 2013, ha scritto:

> 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<javascript:;>
> 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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