[time-nuts] Temex LPFRS-01 / LPRO rubidium reference repair

Magnus Danielson magnus at rubidium.dyndns.org
Thu May 8 02:11:27 UTC 2014

Hej Ulf,

On 05/08/2014 01:14 AM, Ulf Ralberg wrote:
> Bought an LPRS-01 on eBay too. Of course it only locked for a few
> seconds. Got some valuable hints from Magnus Danielsson that steered me
> in the right direction - the VCXO was probably saturated. After some
> inspection, I conluded there were no trimcap to set VCXO mid frequency.
> But there is a trimpot associated to the 20 MHz crystal circuitry, just
> in front of the 20 MHz Xtal (the bigger one of two attached to the
> physics package).

Actually, this is the trimcap which sets the VCXO mid frequency.
Good that you found it and reported on it here.

> The said trimpot was originally set to about 1 o'clock
> and fixed by lacquer. Removing the lacquer and turning it CCW about
> 30-40 degrees gave good values reported back from the 'M' command _after
> locking_:
> 8C 70 BF AB 80 80 AB DA
> Now my LPRS works like a dream, thank you Magnus!

You're welcome!

Oh, welcome to the time-nuts! Maybe introduce yourself and tell us a 
little about your rig and what you are doing. :)

Back in the days, Ulf and I worked for the same company.


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