[time-nuts] TrueTime NTS-100 Innards

Jason Rabel jason at extremeoverclocking.com
Wed Dec 6 04:15:51 UTC 2006


I managed to get a TrueTime NTS-100 IRIG (yes it's old I know), and the
first thing I did was pop open the chassis. ;) I was amazed how little space
was actually used by the card and power supply, plenty of room to add other
time stuff (maybe I can fit in a GPS and a Soekris board). I don't have
anything that can output IRIG-B yet, but I just couldn't pass this up.

Anyhow, I contacted Symmetricom about a PDF manual, and they were nice
enough to send me one (I also got the GPS version manual from someone else -
if anyone wants either let me know). It only gives the basic commands and
nothing about the various jumpers and headers on the board. I tried my best
to squeeze out some tech info from the Symmetricom guy but no luck. Also a
firmware upgrade he said would cost at least $250 and he didn't know if it
was still available (not really worth it since I bought the unit for only
$100).

I started probing around with my oscilloscope and frequency counter and have
made a few discoveries and have a few hunches. Does anyone else have a
NTS-100 (either GPS or IRIG or PPS)? It would be especially helpful if you
have some non-standard options. If you do, can you snap a few high-res pics
of the board so I can see how you jumper layout compares?

The 10 MHz output was the first thing I found, it was quite obvious as the
connector was similar to the alarm. I think I have found the jumper to
disconnect the onboard VCTCXO (and wire in an external OCXO or whatever),
and the tuning voltage pin. Without having an IRIG signal going in it
doesn't bother to try and steer the oscillator any so I can't fully test
this out yet.

I'll probably pull the board out tomorrow so I can follow the traces on the
bottom side. Also I want to drill a hole and mount a BNC connector for the
10 MHz output. It may be old but it is an interesting little piece of
technology, and it still works. The inside was extremely clean, no dust or
anything, like it just came off the assembly line.





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