[time-nuts] Fwd: FE-5680A Physics package

paul swed paulswedb at gmail.com
Mon Oct 31 23:54:49 UTC 2011


I had suggested using the heat gun approach way back in the thread. But
from the pix its not going to help. The cell is clean from what I can see.
So possibly it did leak out. Or the rf exciter has gone bad. Thats actually
what I have run into.
The heating works when you look at the bulb and see RB crud on the glass.
Thats when the heating revaporizes it and really gets the bulb back into
service.
Regards
Paul
WB8TSL

On Mon, Oct 31, 2011 at 9:41 AM, Peter Bell <bell.peter at gmail.com> wrote:

> That FE-5680A (the "non-programmable" one) is the same as the 2 units
> I have - I have seen the "heat a lamp with a heat gun" trick before
> when I was playing with the FRSs - but in this case the actual lamp is
> fine - the problem seems to be with the absorption cell (or possibly
> the other one, which I suspect may be a filter). I've never seen these
> go bad in any of the other units I've seen.  I guess I could try
> re-consolidating the Rb into that little pinch and see what happens.
>
> I'm also not sure the heat gun trick is going to be very practical for
> the lamps on these units - the RF exciter coil seems to have been
> stuck onto the lamp with RTV and then the whole assembly stuck into
> the lamp housing using a big dollop of RTV at the back.  You possibly
> could release the lamp, but it looks like you would have a good chance
> of destroying the drive coil in the process.
>
> I've also been trying to figure out what the RF architecture of these
> units is - it certainly seems to be different from the older ones; for
> a start, the DDS chip is now an integral part of the control loop and
> is generating at least part of the modulation used to interrogate the
> resonance cell (the DDS is clocked with 20MHz and generating
> ~5.312MHz, but the Fselect pin is being driven by a 416.6...Hz square
> wave coming from the Xilinx PLD and it's output is mixed with the
> 60MHz from the VCXO and fed to the snap diode on the physics package
> multiplier assembly.
>
> Once I get a better handle on how it all works, I guess I should write
> it up for the benefit of anyone else trying to fix these things - but
> right now it's in the "unannotated photographs and cryptic notes"
> phase :)
>
> Regards,
> Pete
>
> On Mon, Oct 31, 2011 at 8:32 PM, J. L. Trantham <jltran at att.net> wrote:
> > That's it!  Plus, more information.
> >
> > I knew most everyone would be better organized than I am.
> >
> > Joe
> >
> > -----Original Message-----
> > From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> > Behalf Of Mark Detering
> > Sent: Monday, October 31, 2011 7:22 AM
> > To: Discussion of precise time and frequency measurement
> > Subject: Re: [time-nuts] Fwd: FE-5680A Physics package
> >
> >
> > Here is a page that has some information on the FE-5680.
> > http://vk3um.com/Rubidium%20Intro.html
> > Near the bottom the is a link to an article by VK3GJM that talks about
> > rejuvinating Rb lamps. This may be of help.
> >
> >> Peter,
> >>
> >> Somewhere, I have read an article about 'resurrecting' a 'dead' Rb
> >> bulb.  I think it was done with heating but I do not recall.  I
> >> probably have the article squirreled away somewhere and I can probably
> >> chase it down if someone else on the list does not come up with the
> >> link first.
> >>
> >> Are you familiar with what I am talking about?
> >>
> >> Joe
> >>
> >
> >
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