Fwd: FE-5680A Physics package
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.
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
tricks.
So good luck.
Regards
Paul.
On Sat, Oct 29, 2011 at 12:54 PM, Peter Bell bell.peter@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.
time-nuts mailing list -- time-nuts@febo.com
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and follow the instructions there.
Following up on my own post - it seems it is the Rb cell that's the
problem - I swapped the cell over (it's just held in place by hot
glue) and fault moved with the one from the bad unit. After removing
the heat-shrink, there are two separate glass cells in the assembly,
as I suspected. The smaller one (on the left in the photo) was the
one closest to the lamp and if it contains anything at all, it's not
visible. The second, slightly larger, cell seems to be the actual
absorption element and contains a small quantity of some silvery metal
(I.E. Rb) partly in the pinch and partly deposited on the glass.
It all looks so simple it's hard to see what the problem could be -
the only thing I can think of is that the first cell has leaked (the
second one obviously hasn't, since the Rb is not oxidized). The other
conclusion that I've reached from this is that these units are pretty
non-critical - as long as I used the good Rb cell assembly, it would
lock with any combination of housing / heater / photocell, RF
multiplier assembly and C-field coil / shield. Ah well - put it to
one side until / if I get another dead unit, I guess.
Regards,
Pete
On Sun, Oct 30, 2011 at 3:31 AM, paul swed paulswedb@gmail.com wrote:
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
tricks.
So good luck.
Regards
Paul.
On Sat, Oct 29, 2011 at 12:54 PM, Peter Bell bell.peter@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.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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and follow the instructions there.
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
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Peter Bell
Sent: Monday, October 31, 2011 1:00 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Fwd: FE-5680A Physics package
Following up on my own post - it seems it is the Rb cell that's the problem
- I swapped the cell over (it's just held in place by hot
glue) and fault moved with the one from the bad unit. After removing the
heat-shrink, there are two separate glass cells in the assembly, as I
suspected. The smaller one (on the left in the photo) was the one closest
to the lamp and if it contains anything at all, it's not visible. The
second, slightly larger, cell seems to be the actual absorption element and
contains a small quantity of some silvery metal (I.E. Rb) partly in the
pinch and partly deposited on the glass.
It all looks so simple it's hard to see what the problem could be - the only
thing I can think of is that the first cell has leaked (the second one
obviously hasn't, since the Rb is not oxidized). The other conclusion that
I've reached from this is that these units are pretty non-critical - as long
as I used the good Rb cell assembly, it would lock with any combination of
housing / heater / photocell, RF multiplier assembly and C-field coil /
shield. Ah well - put it to one side until / if I get another dead unit, I
guess.
Regards,
Pete
On Sun, Oct 30, 2011 at 3:31 AM, paul swed paulswedb@gmail.com wrote:
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 tricks. So good luck.
Regards
Paul.
On Sat, Oct 29, 2011 at 12:54 PM, Peter Bell bell.peter@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.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
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and follow the instructions there.
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
That's it! Plus, more information.
I knew most everyone would be better organized than I am.
Joe
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@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
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
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@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@febo.com [mailto:time-nuts-bounces@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
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
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@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@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@febo.com [mailto:time-nuts-bounces@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
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
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and follow the instructions there.