[time-nuts] PM6681 and Timelab (was: PM6680 or 53131A for TimePod)

Bob Camp kb8tq at n1k.org
Wed Nov 18 07:35:20 EST 2015


The coin cell / backup battery swap out is something we probably will become more familiar
with on a *lot* of gear. The battery backed up RAM idea is now old enough that there is a large
population of test gear / radios / telecom gear out there with this “feature”. In some cases the 
loss of the battery is a temporary issue. In a lot of others it’s a significant problem. 

If you are buying a piece of gear that has important stuff in RAM, the big question is — has the 
data been lost already? I have bought gear that had a good battery in it, but bad data. If the gear
comes up with “data lost” on the screen, that’s easy to spot. In most cases …not so easy at all. 

Some gear might be configurable by normal means. Almost everything I’ve seen needs a “factory
only” shoot from a test set that probably no longer exists. Yes, there’s nothing magic in that test
set. The RAM just has bits in it. Figuring out what all the bits need to be without any documentation 
is not easy. 

One might hope that as the gear becomes obsolete, the information about what’s what would be 
released to the public. Based on … errr …. on the job experience - not so likely. The data rarely 
is documented in a “public compatible” fashion. One guy’s notes tell you what the test setup looks like.
Another set of notes go into the code. Both are buried in log books from who knows when. Beyond
this, someone actively has to agree to release “corporate IP”. The complex part of that is the fact 
that the calibration techniques probably live on in a modern piece of gear. Not at all easy ….


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