[time-nuts] Trimble GPS board

Bob rbenward at verizon.net
Sat Aug 22 14:02:35 EDT 2015

Hi Arthur,
Thank you for this information.  I have not received my board yet, I 
probably still have a few weeks to go.  The LT1764 will take up to 20V, 
but I would never go to the edge.  You could easily do 12V, the only 
downside is the dissipation in the LT17654.  Use a variable power supply 
and raise the voltage slowly.  Monitor the temperature with a 
thermocouple,  IR spot meter (radio shack had one for $10), or just use 
your finger.  If you can keep your finger on it comfortable for a long 
period of time, the temp should be OK.  The junction temp is rated for 

Now on the flips side, my only concern is the regulator is not supplying 
the oven power.  Most Trimble OCXOs I see on Ebay are powered by +12.  
When supplying only 6.5V the oven might not get up to temp producing 
frequency instability and some erratic EFC stats.

See below, here is a 73090 OCXO (same as on some of those GPSDO boards) 
powered by +12V.  It's possible the regulator is meant to be powered 
from +12V, supplying power to the digital logic and to the oscillator 
portion of the OCXO. Then +12V directly supplies the oven.


I will post my success and let everyone know how I make out.  I 
purchased this to have a backup for my Z3801 & Z3805.  Both are on the 
fritz, I will be post those trials and tribulations on a new thread.  
Thanks so much for your response.


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