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, [email protected] 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 <[email protected]>: > 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, [email protected] > 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 > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
