Symmetricom NTS-200 Time Server

[YetAnotherTechie]

Hello,
I've been following this thread and just have to ask...
I saw on one of the datasheets above that the timing accuracy is at least 150ns plus a few millis once you add the other network overheads. There's been a lot of progress on GPS chipsets in the last 20(!) years, have you considered using a modern timing unit like ublox M8T and say a raspberry pi or similar?
Don't get me wrong, i know and love fixing old gear, but i also consider the performance of the fixed unit and the usefulness of the knowledge i gain repairing it, and to me this units seem like a bad proposition?

[smgvbest]

I have and use a Pi3 + ublox as a stratum 1 time source with fall back to ntp servers as a Stratum 2 time source.   My usage is in Astronomy and keeping my PC set so that images have a accurate timestamp.

for me this is a fun problem to solve, Just wanted to see if I could do it while learning some reverse engineering techniques.

[acfnews]

Hi,

Also totally aware of the (better) possibilities of other hardware. The remote site where the NTS-200 was located also has a newer GPS stratum1 timeserver used in an IoT gateway. The NTS-200 has more emotional value than technical value, and still I think messing around with it is a learning process...

Best regards,

Ron

[smgvbest]

I have not fixed mine yet.
I am convinced until you resolve the incorrect time coming from the P60ARM/GPS you're not going to have a reliable fix.
Problem I have is my EPROM read does not read the 16bit eproms used by this controller nor does the JTAG interface support reading them from what I can tell.   it has a limited JTAG version 1 implementation.
I'm not a JTAG expert but even if I could get a dump of the memory i have no way to write new eproms.   

I did find the AT49F1025 are a pin compatible replacement but are also very hard to find and my programmer does not support them either.   the 8 bit version yes,  not the 16 bit version

[InFoq]

I'm wondering if a linux ntpd or other daemon between nts200 and clients can correct the gps epoch correctly.

not a solution for everyone...but it was not too difficult to program NFQUEUE processes in C on my linux (running ntpd client) to do the timestamp offset corrections in each traffic direction.  Turned out simplicity of NTP protocol being self-unaware enough to allow this to work quite well!  Not sure how non-deterministic the OS's NFQUEUE mechanism is, but NTP's PLL corrections should not be much worse than for other worst-case internetworking jitters... E.g. MitM mangling set-top-box protocol:
https://xakcop.com/post/mitm-stb/

[Uky]

Reviving this thread, I picked up one of these NTS-150's
on a flea market.

While the unit is indead dead regarding the date roll over,
I am considering using it as a 1 second (precision) source...

It does find a lot of satellites and are able to track many of them.
Time is correct (but not date).

Has anyone been able to figure out a signal on the PCB
that can be used as a source? There are two LED's flashing
with 1pps ... but they do this also with no antenna connected...

Ulf

[geerlingguy]

Has anyone been able to figure out a signal on the PCB
that can be used as a source? There are two LED's flashing
with 1pps ... but they do this also with no antenna connected...

I'm not sure of the architecture of this specific box, but most of the time, a PPS signal is driven by the onboard oscillator, which is steered by the GPS PPS, which can come and go. Some devices I've seen will drop PPS if GPS drops out for a period of time, but others will keep pumping out the pulse every second indefinitely, allowed to wander off the GPS over time. I assume that's the case here.

I was just given one of these, and may take a crack at taking some of the already great investigative work here, and seeing if I can get a fix. Will take time though.