[time-nuts] Zeeman frequency oddness
Tom Van Baak (lab)
tvb at leapsecond.com
Sun Oct 28 13:57:29 EDT 2012
I'll send you a known working 10368A.
On Oct 28, 2012, at 1:36 PM, John Ackermann N8UR <jra at febo.com> wrote:
> Thanks to all for the helpful replies.
> At this point, I believe what happened is that the degausser isn't working properly and that may have resulted in the tube being more magnetized rather than less; no matter what I do, I am now getting lock at about -5e11 -- which is not what it used to be.
> I've started troubleshooting the 10368A degausser, and it appears that the exponential current decay, doesn't. I fear that op-amp U1 (a pre-IC block labeled Intech A-233) is bad as the voltage driving the darlington pair is stuck at 14.5 and doesn't decay with time. I hope that the A-233 is just a potted, discrete transistor, generic opamp, so I suspect that I can dead-bug something like an LM358 in its place.
> If anyone else has encountered this situation, I'm all ears...
> cdelect at juno.com said the following on 10/28/2012 11:50 AM:
>> After the degauss you should recheck the Zeeman setting, which you did.
>> You also verified the synthesizer frequency is set to the frequency that
>> requires a C-field current high enough to reach 53.53.
>> Since it is running at 48.21 you should increase the C-field setting
>> until the central peak moves to 53.53.
>> This is assuming that your unit has the resistor installed for 53.53.
>> If not you will reach the end of the C-field pot before getting to 53.53!
>> In that case you need to put a decade box (set to max resistance) across
>> the C-field resistor and with the C-field set to 500 reduce the
>> resistance until the central peak gets to 53.53.
>> Then solder in a 1% fixed resistor (closest value to the decade box
>> reading) across the C-field resistor.
>> Now recheck and you will be able to use the C-field pot to reach exactly
>> Corby Dawson
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