FE 5680A Warning
The FE 5680A's advertised as NEW are not NEW! A friend that made me
aware of the sale did notice clear signs of use, so I did a closer inspection
under a Microscope and found clear indications that the unit has been
bolted down in the past. Does work fine and I am looking at ways to go directly
to the C field to disciplin the Rb. Does any one have info that would help
to do so.
Bert Kehren Miami
I just bought a couple of 5680A's that have the same FEI p/n. They are
pop-riveted to a heavy double-sided board., obviously cut off from a
longer board. I've removed one of these from it's board/heatsink. There
are two pots on the board, only one of them can be trimmed with the case
on. The sinewave forming filter and maybe countdown chips are not there,
and never were. There are three identical voltage regulators on the
heatsink spine.
I'll be doing some more reverse engineering on these units; they were so
cheap I had to have a couple! If only FEI was more helpful! hey must
have moved on from these, and could put one manual out there?
Oh Well!
Don
The FE 5680A's advertised as NEW are not NEW! A friend that made me
aware of the sale did notice clear signs of use, so I did a closer
inspection
under a Microscope and found clear indications that the unit has been
bolted down in the past. Does work fine and I am looking at ways to go
directly
to the C field to disciplin the Rb. Does any one have info that would
help
to do so.
Bert Kehren Miami
time-nuts mailing list -- time-nuts@febo.com
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and follow the instructions there.
--
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
R. Bacon
"If you don't know what it is, don't poke it."
Ghost in the Shell
Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com
On 11/12/2011 9:46 AM, Don Latham wrote:
I just bought a couple of 5680A's that have the same FEI p/n. They are
pop-riveted to a heavy double-sided board., obviously cut off from a
longer board.
I think those pop-rivets are actually screws with a small hex socket in
the center. That's what was mounting one I got several years ago.
Aha. Well, they were hollow, so I drilled 'em out. Didn't want the big
card anyhow :-)
Don
Rex
On 11/12/2011 9:46 AM, Don Latham wrote:
I just bought a couple of 5680A's that have the same FEI p/n. They are
pop-riveted to a heavy double-sided board., obviously cut off from a
longer board.
I think those pop-rivets are actually screws with a small hex socket in
the center. That's what was mounting one I got several years ago.
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.
--
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
R. Bacon
"If you don't know what it is, don't poke it."
Ghost in the Shell
Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com
RESENT WITHOUT ATTACHMENTS
Fellow Timenuts,
Here are the clues that will answer some of your questions concerning
the newer
version FEI Rubidiums and also its Kissing cousins from Symmetricom;
the newer
series XPRO and SA22c. It appears both companies have came with up with
same idea
at the same time or copied each other to a large extent.
In the old days the Atomic loop was in the analog domain. The loop
output signal
was a fixed frequency and any other frequency was derived from that
fixed
frequency outside of the loop.
These newer devices have incorporated a different paradigm using a
digital control
process for the actual Atomic loop. Thus the output frequency is
truly part of
the loop rather then derived from the loop. The AD9832 provides but a
fraction of
the control loop error signal allowing for adjustments to be made in
steps of parts
in 10 to the minus 13 (10E-13). The C-field adjustment is done with
either an A/D
or some digital potentiometer, but may also have some possible external
access.
The end result is that the output frequency is factory selected by
changing the
frequency of the main crystal oscillator. This makes it very hard to
change a
Rubidium with an odd-ball frequency because of internal firmware.
All of this is gleamed from two (albeit cryptic) documents from
Symmetricom. One
document is on their XPRO unit and the other is on the SA22c unit. In
the XPRO
document carefully read pages 15 through 19 (PDF pg 21-25). Then
carefully read the
SA22c document pages 20 and 21 (PDF same).
Keep in mind that the info is written so as to not give away so-called
trade
secrets. So you have to do some critical thinking and reading between
the lines to
get the whole picture. The XPRO document block diagram on page 16
(PDF-pg 22) is
the primary key to all of the above.
I am including the two aforementioned documents as attachments.
Hopefully they will
get through. If not I will ask Didier (KO4BB) to host them on his site.
Bill....WB6BNQ
Kind of joining in late.
Might this be the epay womart for $49 inclouding shipping?
That really is quite a good price.
May also order one up.
Regards
Paul.
On Sat, Nov 12, 2011 at 5:04 PM, Don Latham djl@montana.com wrote:
Aha. Well, they were hollow, so I drilled 'em out. Didn't want the big
card anyhow :-)
Don
Rex
On 11/12/2011 9:46 AM, Don Latham wrote:
I just bought a couple of 5680A's that have the same FEI p/n. They are
pop-riveted to a heavy double-sided board., obviously cut off from a
longer board.
I think those pop-rivets are actually screws with a small hex socket in
the center. That's what was mounting one I got several years ago.
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.
--
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
R. Bacon
"If you don't know what it is, don't poke it."
Ghost in the Shell
Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com
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's it, I think. Look for the large base and the extra crystal,
completely extraneous.
Don
paul swed
Kind of joining in late.
Might this be the epay womart for $49 inclouding shipping?
That really is quite a good price.
May also order one up.
Regards
Paul.
On Sat, Nov 12, 2011 at 5:04 PM, Don Latham djl@montana.com wrote:
Aha. Well, they were hollow, so I drilled 'em out. Didn't want the big
card anyhow :-)
Don
Rex
On 11/12/2011 9:46 AM, Don Latham wrote:
I just bought a couple of 5680A's that have the same FEI p/n. They
are
pop-riveted to a heavy double-sided board., obviously cut off from
a
longer board.
I think those pop-rivets are actually screws with a small hex socket
in
the center. That's what was mounting one I got several years ago.
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.
--
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
R. Bacon
"If you don't know what it is, don't poke it."
Ghost in the Shell
Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com
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.
--
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
R. Bacon
"If you don't know what it is, don't poke it."
Ghost in the Shell
Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com
I can let you know what I've found out about these units - I got given
a couple of dead ones and did a bit of poking around trying to get
them working. I didn't get that far, since one of the units was
easily fixed (the MAX882 3.3V regulator had failed) and the other
seems to have a faulty Rb absorption cell (it works if you swap the
cell from the other unit into it).
The first is, as you noticed, that they have 3 voltage regulators -
but apparently couldn't spare one to generate the +5V line - they seem
to run (1) The Rb lamp / heater (the one nearest the connector) (2)
the cell heater (the middle one) and (3) the analog electronics @8.8V
(the last one).
The quickest way to verify this is to apply +15V / GND to pins 1 and 2
of the d-type and then check the voltage on the VCC pin (20) of the
74ACT240 buffer chip next to the connector - there is no 5V there.
There is also no 5V on pin 5 of the MAX882 - and hence no 3.3V line.
There is a connection between these points and pin 4 of the d-type -
and applying an external +5V to this pin will bring up the 3.3V line
and allow the unit to lock. When locked, pin 3 on the d-type goes
low, and will sink enough current to operate an LED.
Pin 5 is also connected to GND, and was (on the original PCB) also
connected to the ground plane along with pin 2. It doesn't seem to be
actually necessary, as the unit will operate with a single ground
connection, but would it would seem to be good practice to use this
pin, too.
It's been alleged that pin 6 is a 1PPS output - but I can't see
anything on it at all except a constant logic 1 - I tried changing the
'ACT240 in case the buffer was damaged, but this had no effect, and
the pin is still a constant 1. I suppose it's possible that there is
an extremely narrow -ve going pulse on it, but if there is it's too
narrow for the trigger circuit on my (100MHz) scope to see it.
Pin 7 outputs a 10MHz sine wave - about 800mV p-p unloaded. I haven't
put it into an analyzer, but it looks pretty good.
Pin 8 and 9 are connected to the MAX3232 on the board, and from them
onto the serial port on the DS80C323 CPU. Pin 8 is RXD, pin 9 is TXD
(from the unit's point of view). This serial port accepts the commands
described in the FEI document that's floating around the net for
trimming the oscillator. They appear to operate as described.
Internally, the main VXCO runs at 60MHz - it's buffered and fed into
the Xilinx XC9572XL PLD on the back of the board. This chip appears
to contain mostly frequency dividers - it generates the 10MHz output,
20MHz for the MCLK to the DDS chip (although with a slightly nasty
40:60 duty cycle) a 416.6666Hz drive for the fselect pin on the DDS
chip, a 833.33333Hz drive for the lock in amp. There are also a bunch
of signals that go to the test connector, and are presumably used for
factory programming.
The output of the DDS is about 5.3MHz with FM on it at a 416.666Hz
rate - this is mixed in with the 60MHz output from the VCXO to give
the drive signal to the snap diode in the physics package.
There are 3 pots on the board - the one that's normally accessible via
a hole in the case seems to be intended as a C-field adjust, but does
nothing on the units I have - the other one near it appears to trim
something in the photocell amplifier circuit. The one on the other
side of the board (near the VCXO) sets the bias on the snap diode
That's all I've got, since I then worked out that I didn't have an
electronics problem - hope it helps.
Regards,
Pete Bell
On Sun, Nov 13, 2011 at 1:46 AM, Don Latham djl@montana.com wrote:
I just bought a couple of 5680A's that have the same FEI p/n. They are
pop-riveted to a heavy double-sided board., obviously cut off from a
longer board. I've removed one of these from it's board/heatsink. There
are two pots on the board, only one of them can be trimmed with the case
on. The sinewave forming filter and maybe countdown chips are not there,
and never were. There are three identical voltage regulators on the
heatsink spine.
I'll be doing some more reverse engineering on these units; they were so
cheap I had to have a couple! If only FEI was more helpful! hey must
have moved on from these, and could put one manual out there?
Oh Well!
Don
The FE 5680A's advertised as NEW are not NEW! A friend that made me
aware of the sale did notice clear signs of use, so I did a closer
inspection
under a Microscope and found clear indications that the unit has been
bolted down in the past. Does work fine and I am looking at ways to go
directly
to the C field to disciplin the Rb. Does any one have info that would
help
to do so.
Bert Kehren Miami
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.
--
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
R. Bacon
"If you don't know what it is, don't poke it."
Ghost in the Shell
Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com
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.
Hi Rex,
Those fasteners are both "pop rivets" and screws. They are an advel design of light alloy rivet with an external thread and a hexagonal head on the die. They fasten with standard automatic riveting equipment but can be removed and re-installed with a allen (hex) key. They work very well.
Robert G8RPI.
From: Rex rexa@sonic.net
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Saturday, 12 November 2011, 21:58
Subject: Re: [time-nuts] FE 5680A Warning
On 11/12/2011 9:46 AM, Don Latham wrote:
I just bought a couple of 5680A's that have the same FEI p/n. They are
pop-riveted to a heavy double-sided board., obviously cut off from a
longer board.
I think those pop-rivets are actually screws with a small hex socket in the center. That's what was mounting one I got several years ago.
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.
On 11/13/2011 10:36 AM, Peter Bell wrote:
I can let you know what I've found out about these units - I got given
a couple of dead ones and did a bit of poking around trying to get
them working. I didn't get that far, since one of the units was
easily fixed (the MAX882 3.3V regulator had failed) and the other
seems to have a faulty Rb absorption cell (it works if you swap the
cell from the other unit into it).
Here is a pile of photos I did while fixing one of mine. In this one
the oscillator had drifted high, and wouldn't lock when warm. A tiny
nudge to C217 and it is happy, the output should sweep to about 4ppm high.
I suspect the PTC element on the xtal is dodgy too; It seems slower to
settle than the other units.
I figured they might be useful when trying to point out components and
test points.
/Kasper Pedersen