[time-nuts] Thunderbolt "osc age alarm", where to get replacement oscillator?

Bob Camp kb8tq at n1k.org
Fri Nov 13 21:34:06 EST 2015


I think you will find that tearing open a TBolt OCXO does not reveal a mechanical trimmer
anywhere to be seen. That’s true at least if it was made past about 1997 …

It’s unusual to see them actually age out. Most that I have seen still have > 90% of their trim
range left. A much more common situation is a shorted or open EFC line. Sometimes the 
issue is outside the OCXO on the TBolt pc board. Other times it’s inside the OCXO. The quick 
check is to watch it on a counter and try to swing the DAC. If the frequency does not change….
you have an open or a short. 


> On Nov 13, 2015, at 5:58 PM, Chuck Harris <cfharris at erols.com> wrote:
> Typically all that means is the crystal needs to have its
> trimmer capacitor adjusted back into range.  I have no direct knowledge
> of the TBolt's oscillator, but it might be as simple as removing
> a screw, and adjusting the trimmer... Or, in some cases you have
> to remove a solder blob from the metal can, and access the trimmer.
> I would sure hate to toss away all that hard earned aged xtal for
> a new one at this point.
> -Chuck Harris
> Pete Stephenson wrote:
>> Hi all,
>> Lady Heather just reported that my Thunderbolt's "osc age alarm" just activated.
>> The manual tells me this means that the oscillator control voltage is
>> at a rail and that the oscillator should be replaced. It says this
>> shouldn't be needed during the first 12 years of service, but mine is
>> ~17 years old, so its time may have come.
>> Where can I find a suitable replacement oscillator? Is there a
>> recommended part number? If the original part is no longer available,
>> what is a good substitute?
>> Cheers!
>> -Pete
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