[time-nuts] Symmetricom Power On Counter

Bob Camp kb8tq at n1k.org
Mon Jul 25 16:45:22 EDT 2016


Maybe it only has a 20 year life if you power it up 50% of the time :)
Somehow I doubt that it only has a 10 year “power on” life. 


> On Jul 25, 2016, at 3:55 PM, Skip Withrow <skip.withrow at gmail.com> wrote:
> Hello Time-Nuts,
> I just ran a Symmetricom X72 for 10 days to check the rate of the Pwr HRS
> counter.  At one point I thought I did this with an SA.22c and found a
> discrepancy between actual number of hours run and the counter increment.
> I can report that the X72 does appear to count hours correctly.  After
> running for 233 hours the hex counter incremented by 233 decimal.
> This leaves me with some questions though.  The counter in the unit is four
> hex digits giving a max count of 2^16 or about 65,000.  The life of the X72
> is supposed to be about 20 years (roughly 180,000 hours).  So what happens
> to the unit on overflow, does the counter just rollover?  So how do you
> tell a new unit from one with 70,000 hours on it?  And there is also a
> service bit that is supposed to switch when there are several months of
> life left, what drives this bit?  Is it some kind of lamp life measurement
> (like the LPRO), and is the power on counter involved in any way?
> The Symmetricom X72 and SA.22c seem to be cousins, I have not played with
> an X99 and don't know if it is related.  If someone has insight into these
> units I would be most interested in knowing some of the answers.  In fact,
> the 'w' command dumps about 26 different values (all in hex) and having the
> secret decoder ring for what the item mnemonics are and the scaling of the
> displayed values  would be very useful.  The user manual lists the 'w'
> command but gives no information regarding the resulting display that I can
> find.
> Thanks in advance for any help.
> Regards,
> Skip Withrow
> 303-790-1830
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