Do you have the service manual? If not, get it here...
http://www.ko4bb.com/manuals/index.php?dir=05%29_GPS_Timing/Efratom
As I recall there's pretty good trouble shooting in the manual. Several
years ago I fixed an FRK-H that wouldn't lock. The crystal osc had
drifted enough that the trimmer didn't have enough range to tune to the
lock freq. Fix was to pull one small cap that was in parallel with the
trimmer. (C-11 on Osc schematic A21.)
If you have a counter that you trust, it should be easy to see if tuning
is reasonable. The manual will show where the trimmer is. I think I
recall looking at the modulation signal as shown in fig 3-2 in the
manual as I didn't have an accurately calibrated counter at the time. (I
wasn't able to get to a balanced 2fm output signal until I modified the
circuit.)
On 2/8/2013 6:50 PM, Garren Davis wrote:
I've let it run for hours and it gets warm. It has a heat sink and it all gets
warm. There are two adjustment screws. One under the heat sink and one on the
side of the unit. Is one for the vco and the other for the C-field?
On Feb 8, 2013, at 4:53 PM, "jmfranke"<[email protected]> wrote:
How long do you let it run? Does the crystal oscillator oven get warm? If you
let it run more than 15 minutes, and the oven gets hot, the next thing to check
is the output frequency range as the tuning voltage sweeps. Not having a
frequency counter hurts but there are other methods. One is to use WWV on 10
MHz. You should hear the output slowly sweep through WWV, first on one side of
zero beat and then through zero beat to the other side. If the beat stays on
one side, the VCO needs tweaking to get the sweep somewhat symmetrical about
the 10 MHz WWV signal.
John WA4WDL
--------------------------------------------------
From: "Garren Davis"<[email protected]>
Sent: Friday, February 08, 2013 7:12 PM
To:<[email protected]>
Subject: [time-nuts] FRK-L Rubidium
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 garage and I'd like to put
them to use. Any help would be appreciated.
Garren
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
