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

paul swed paulswedb at gmail.com
Sat Oct 29 15:31:10 EDT 2011

My comments have been about other rb cels and the fact that components in
the rf oscillator tend to die and are generally replaceable. Additionally
using the practice of heating the emission cell with heat gun to
re-evaporate the accumulated rb seems to really revive a cel. So if its
dead what the heck have some fun. I wrote up my info and its on Diddiers
and Stanleys sites. Others like Magnu's and Stanley have written up their
So good luck.

On Sat, Oct 29, 2011 at 12:54 PM, Peter Bell <bell.peter at gmail.com> wrote:

> I was wondering if anyone on the list has ever had a play with these
> things?  I had a couple of dead ones, and have managed to get the
> first one working (easy fix - the 3.3V regulator was dead), but the
> second seems to be a lot more troublesome.
> Basically, everything seems to be working, but there is no resonance
> dip detected at the photocell - however all the individual parts seem
> to be OK.  I did a couple of quick and dirty tests firstly by swapping
> the entire Rb cell assembly over between the two units - and the fault
> swapped over with the Rb cell.  Both cells are running at the same
> temperature, the photcells are good, and the working one still works
> (on both main boards) even when you swap the snap diode / filter
> assembly or the shield / c-field coil from the bad one.
> Basically, all that's left is the photocell (which seems to pick up
> light OK), the FET / Thermistor (unlikely, since the heater works
> correctly), the lens (looks perfect) and the Rb cell itself.  So I'm
> tending towards the "bad Rb cell" idea - but the problem is that I've
> fixed quite a few Rb oscillators in the past (mostly Efratom FRKs and
> a few FRSes) and I've never seen a bad Rb cell.  So I was wondering if
> anyone else on this list thought it seemed likely.
> (resent with the photo reduced in size).
> Incidentally, when I was looking at the Rb cell, I noticed that it
> seemed to be a pair of cells held together in a heat-shrink tube - I
> assume that the first (slightly smaller) one is a isotopic filter and
> the second is the actual absorption cell?
> And does anyone have any schematics for these things?  FEI seem to
> have the standard "send it back to us" approach that is increasingly
> common recently - another reason I liked the FRSes.
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