It is possible to open the can if you are careful. A good vacuum desoldering
tool is a good start to remove as much of the solder as possible. Then one
would peal the can open a bit at a time. Then you need to find out where the
failure is.
But to answer your question, yes just buy one, it's much easier. But first
check that there is power to the heater.
----- Original Message -----
From: "Garren Davis" <garren.da...@qlogic.com>
To: "Discussion of precise time and frequency measurement"
<time-nuts@febo.com>
Sent: Monday, February 11, 2013 12:01 PM
Subject: Re: [time-nuts] FRK-L Rubidium
Ed, Bob,
This morning I noticed the crystal control voltage was down to 11 volts.
I'll let it keep running to
see if it drops any further. The tuning capacitor is adjusted out about as
far as I want to set it. Any
further and I think the adjustment screw will fall out. I did remove C11 as
an experiment to see what
it would do to the frequency. It dropped a lot so now I know I can put a
smaller one in if I need more
adjustment.
Next up is the Tbolt. I'm pretty sure the oven heater is not working. Has
anyone taken apart the trimble
oscillator? It looks like it's sealed pretty good. I see quite a few for
sale. Is it just easier to
replace it?
Thanks for all the help.
Garren
-----Original Message-----
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Ed Palmer
Sent: Sunday, February 10, 2013 11:02 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] FRK-L Rubidium
Hi Garren,
Yes, you're right. Silly me, I made the mistake of believing what was
written in the manual which says 2-12 volts. When I measure it, I see
~2-16 volts. Let that be a warning to you. This isn't the first time that
manual has led me astray! I should have known better.
Did you notice that the voltage changes as you adjust the capacitor on the
side? If the adjustment is at it's limit, you may have to change capacitors
A3C11 and maybe A3C12 to get the oscillator back on frequency. It's
explained in the manual. :-) Let it settle for at least a few days and see
which direction the crystal control voltage moves. If it falls you're fine.
If it rises higher, you may want to look at the capacitors. If you have to
change the capacitors, be sure to use NP0/C0G type capacitors.
Bob's comments regarding the C-field are right on the money. It's for fine
tuning after you have a stable lock. It won't help you obtain or maintain a
lock. You won't be able to adjust it without a known, stable
10 MHz reference source like the Tbolt and some good measurement equipment.
Ed
On 2/10/2013 9:27 AM, Garren Davis wrote:
Hi Ed,
The voltage swings from 2v to 17v. Doesn't that mean I have about 4 to 5
volt margin if it's locked at 12 volts?
I had to adjust the capacitor out almost all the way to get it to lock. If
I need to adjust it more can I use the C-field adjustment or should I stay
away from that?
Garren
On Feb 9, 2013, at 10:48 PM, "Ed Palmer" <ed_pal...@sasktel.net> wrote:
Hi Garren,
Congrats on your repair. Since the crystal control voltage is spec'd as
~1 to 12 Vdc, you're apparently holding onto lock by the narrowest of
margins. You definitely want to adjust the oscillator to bring that
voltage closer to the middle of it's range.
Ed
On 2/9/2013 11:38 AM, Garren Davis wrote:
Found my problem with the FRK. R31 on the Osc board was burned and open.
This was caused by a shorted C16. Replaced and it is now locked. The
lock voltage is 12.7v. Is this good or should it be lower?
Garren
On Feb 9, 2013, at 6:10 AM, "Bob Camp" <li...@rtty.us> wrote:
Hi
How old is the FRK? Does it look like it's been run without a heat sink
for very long? They tend to get flaky if run for a while (many months)
without heat sinking. There's nothing mysterious about it. The MTBF of
the parts gets noticeably worse as the unit heats up.
Bob
On Feb 9, 2013, at 1:09 AM, Garren Davis <garren.da...@qlogic.com>
wrote:
Well for some reason the 10 Mhz stopped working on the FRK. Don't know
why. Started up the thunderbolt. It acquired satellites but then the
DAC voltage went to -5 volts. It's been there for an hour. Will this
change after the unit stabilizes? Going to bed. Will check it
tomorrow.
Garren
On Feb 8, 2013, at 8:25 PM, "Ed Palmer" <ed_pal...@sasktel.net> wrote:
Hi Garren,
I suggest that you get the Thunderbolt working first. Without a
known 10 MHz source to compare to, you're flying blind. Once the
Tbolt is running, you should be able to check the frequency of the
FRK by feeding both into your scope. Trigger on the Tbolt and watch
what the FRK does. You should see the trace scrolling in one
direction, then slow down, then stop, then scroll the other
direction. The 'stop' point is at 10 MHz. The frequency sweeps a
total of 20-30 Hz so it's easy to see. If you don't see the 'stop'
point, the FRK isn't getting to 10 MHz. Now use the best frequency
counter you've got to measure the Tbolt. Regardless of the
calibration of your counter, the number your counter gives you
becomes your 'new' 10 MHz. Now measure the FRK to see if it's
running fast or slow.
You should check the temperature of the lamp. It's easy to get at by
removing the cover in the center of the heat sink. Probably best to
remove the cover and then power down before you go poking around
inside! The temperature of the cavity is also important, but getting
to it is more of a hassle - don't go there if you don't have to.
Of course, check for the normal things like internal power supply
voltages, ripple, current drain (both initial and steady-state), etc.
Regarding your second message, yes, the adjustment under the heat
sink near the edge is the C-field. That won't help you at this
point. The adjustment in the center of one side is the VCO. You
could try adjusting it, but like I said, you're flying blind at this
point. You won't know if you're adjusting closer to 10 MHz or
further away.
Good luck,
Ed
On 2/8/2013 6:12 PM, Garren Davis wrote:
Been lurking on the list for a while and finally started playing
with a FRK-L rubidium frequency standard. I've had this thing for a
while and decided to power it up and see what it would do. I do not
get a lock. What I see is the lamp voltage at 8.54 volts which I
think is good but the xtal control voltage swings from 2 volts to 15
volts and back to 2 volts and keeps cycling like that. I don't have
a good frequency counter but I have a 3 Ghz 40 G/sample scope and it
shows that the 10 MHz signal is there. I just don't know how
accurate it is. Has anyone seen a problem like this? Can anyone
point me to a place to start debugging this? I have the schematics
and test tools. I am a test engineer so I'm not afraid to poke
around in the guts of this thing. Hopefully I can get this thing
running. I also have a thunderbolt that I'll get running this
weekend. I don't know how deep I'll get into this time-nuts thing
but I have this nice scope and a Wavecrest sitting in my gara
ge and I
'd like to put them to use. Any help would be appreciated.
Garren
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