[time-nuts] LPRO-101 internals

Mark Sims holrum at hotmail.com
Sat Aug 16 17:12:18 EDT 2008

I am already rather familiar with the workings of rubidium oscillators...  I have built my own before (just for fun,  using a salvaged physics package).  

The LPRO only has one adjustmnent pot (besides the frequency trim pot).  All the other adjustments are trimmer caps and inductors.  The first thing  to try is that select-to-test resistor.  Then the trim pot.  If neither of those makes things better,  I suspect that the inductors and capacitors will not help either.

It is not worth spending more than a couple millichrons trying to reverse engineer the LPRO design when you can buy them for less than $100.  I'd much rather just break out the diddle stick and start diddling the heck out of it...  goes well my philosophy of "If it jams, force it.  It it breaks,  it needed fixing anyway."  Only thing is the darn thing is working now.  I guess the sight of my collection of diddle sticks and that 5 pound sledgehammer in the corner convinced it that it had better start behaving.


things wont get better by fooling around with the trimpots, IMO. Chances 
are some of the pots are quite sesitive, thus impossible to bring back 
to proper settings w/o detailed knowledge about the alignment procedure.

I would refer to the LPRO manual that, unfortunately, doesn't contain 
detailed circuit and alignment information, but at least some basic 
functional diagrams.
Then, put a manual from a well documented Rb (like the FRS) aside and 
try to re-engineer a detailed block diagram. This will show you how much 
it differs from the FRS, and what parts of the FRS manual are or aren't 
useful for your task. It should also show most of the functionality of 
the trim pots. That way, without having turned any pots, you'll have 
learned a lot about how the unit works, and that should be quite helpful 
for troubleshooting.
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