Hi Ed; Thanks for the response. Great logic/detail on potential issues and solutions. The power supply issue seems completely intermittent and when running may be completely fine. That said I am leaning toward the power supply being the issue, it would explain all the issues. I first saw the power supply issue with the batteries installed, I removed the fuse and the missing voltages came up and the unit locked. before with those voltages absent it was displaying the lock light every few seconds after warmup. I had assumed a bad battery had created too great a load on the supply. But it failed to come up again when I rebooted and then came up again the next time I rebooted. It is either zero or correct. I have several problematic 4065's and thought they had 1000B's, I will check if any have a 1111C. It would be easy to swap them and would resolve the question of if these problems are related. The unit I have may actually be locking but outside it's acceptable EFC range. Phase Noise is except ional about -120dB @ 1Hz offset 5MHz.
I will look at solder on the bricks, for the symptoms that could be the issue. Thanks again for your help; Thomas Knox ________________________________ From: time-nuts <time-nuts-boun...@febo.com> on behalf of Ed Palmer <ed_pal...@sasktel.net> Sent: Saturday, July 8, 2017 12:03 PM To: time-nuts@febo.com Subject: Re: [time-nuts] Tuning a Symmetricom 1111C Hi Tom, I have a Datum 4065A standard with a Datum 1111B oscillator. I've never had to tune it, but it appears to be a clone of the HP 10811 so you might get some insights by researching that oscillator. However, if you're having issues with the +-15V supplies, I'd STRONGLY suggest that you resolve those before attempting to retune the oscillator. Circuit information for these units isn't available, but reading between the lines, I note the following: - My unit uses an AD9713BAP D/A converter to drive the EFC. It requires +-5V supplies. - The system monitors +5V, +15V, and -15V, but not -5V so where is -5V coming from? I see an LM320-5V on the mainboard near the D/A converter. My first guess is that -5V is derived from the -15V supply. If that's true, flaky +-15V supplies will almost guarantee a flaky EFC. Since your unit was able to lock once, it further suggests that retuning isn't required. There's a power supply board bolted to one of the side panels that uses a couple of DC-DC bricks. I found some bad solder joints on that board. I can't remember the details. You might want to check that out. Since these units are microprocessor controlled and include multiple tests and measurements to ensure that the lock is on the correct signal peak I don't think it's going to lock to the wrong peak. You should also be aware that these units use a STEL-1173 chip to drive the D/A converter. This chip is infamous for failing after a few years. If you search the archives you'll find more info on that topic. I found a source for this chip a few years ago, but it looks like that source has dried up. Ed On 2017-07-08 10:00 AM, Tom Knox <act...@hotmail.com> wrote: > Hi All; > > Does anyone have a data sheet or experience with the Symmetricom 1111C, I > have one in a Symmetricom 4065C and the internal diagnostics say it is at the > end of it's tuning range. Is there a way to do a coarse manual adjustment, or > is it a possibility the Cesium is locking to a side peak? In addition the +- > 15 volt supplies have failed to switch on twice during testing, but have > switch on after rebooting. On one reboot it locked quickly. > > Thanks; > > Thomas Knox > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts time-nuts Info Page - American Febo Enterprises<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts> www.febo.com time-nuts is a low volume, high SNR list for the discussion of precise time and frequency measurement and related topics. To see the collection of prior postings to ... and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
