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

Bob Camp kb8tq at n1k.org
Sat Nov 14 17:33:15 EST 2015


Hi

> On Nov 14, 2015, at 8:01 AM, Pete Stephenson <pete at heypete.com> wrote:
> 
> On Sat, Nov 14, 2015 at 12:00 AM, Bob Camp <kb8tq at n1k.org> wrote:
>> Hi
>> 
>> First thing to check is that it really *is* at limit. There apparently are a few odd things
>> that can trigger the alarm.
> 
> What sort of odd things might cause that?

Since we do not have an exact firmware dump of any of the TBolt firmware (let alone a
dump of each version) it’s only a guess as to what can trigger the alarm. What I have seen
are OCXO’s that trigger it without being at either end of the tune range. What I would guess
is that there is some sort of aging estimation going on. 

> 
> It was weird: yesterday LH highlighted the DAC value which was around
> 0.38V (I didn't write down the number, alas) and the "osc age alarm",
> both of which were red.

Which is the sort of thing I have seen. 

> 
> I did a factory reset for good measure and things cleared up. The DAC
> value is now around 0.42V and the alarms are off and everything is
> green. The OSC plot in LH tracks the DAC value, so it appears that the
> Thunderbolt is able to control the oscillator reasonably well.
> 
> What's the max range that the DAC can produce? +/- a volt? Two?


The DAC range is +/- 5V. The OCXO’s apparently start out from the factory 
set to center at 0V. If that’s true, your 0.4V OCXO has aged less than 10% of the
range in how ever many years since it left the factory. 

> 
>> The OCXO’s out of the TBolt are sold on the auction sites from time to time. They
>> seem to go for < $40 delivered. The footprint on the OCXO is pretty standard. You
>> can tune the parameters on the TBolt. There are a lot of other choices. About the only
>> real limit is the 10 MHz frequency.
> 
> Cool. I see a bunch of Trimble and non-Trimble oscillators for sale on
> eBay but would hate to get the wrong one. Does it need to be the exact
> same model number, or are they usually all compatible (assuming that
> they are 10MHz and use the same voltage for the oven and other
> electronics?

I would go for a proper TBolt part. I’d get one with the most recent date code
you can find. Newer is always better :) To get the right sort, I’d take Tom up 
on his offer. It sounds like the best deal I’ve heard.

Bob

> 
> Cheers!
> -Pete
> 
> -- 
> Pete Stephenson
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