[time-nuts] Vectron GPSDO Oscillator stranges...
Burt I. Weiner
biwa at att.net
Sat Jan 12 05:30:23 UTC 2013
Just to give the group and update... The Caritronic switching supply
in the DATUM 9390 completely failed this afternoon, so obviously it
was on its last leg. I did find Caritronics and they are very nice
people, but expensive. My friend Stu, K6YAZ told me he had a Cisco
power supply model ADP-30RB, which puts out +12 VDC at 2.0 AMPS, -12
Volts at 0.200 AMP, and 5 Volts at 3.0 AMPS. Sounds like just what I
need and it's about the same size as the DATUM outboard 12 Volt
supply that comes with the 9390. He brought it over this evening and
I was going to test it and then connect it up and see if that would
solve my problem. I quickly discovered however, my wife had other
plans for me for this evening. I may be able to do a little in the
morning, but most likely not till Monday afternoon. The ADP-30RB is
readily available on eBay (I bought two more that are guaranteed for
a total of $12.00). I'll let you know how this progresses.
Burt, K6OQK
Ed,
Thanks for you suggestions. I took a look at the control line and
saw about 100 mV of "grunge" and then took a look at the +12 volts
going to the oscillator and saw about 2 volts of the same stuff. I
then went and took a look at the DC to DC Converter's output and say
the same about 2 volts of grunge and about 1 volt of grunge on the
-12 Volt line. The 5 Volt line looks fine. I need to cobble up a
+/- 12 Volt supply (ref to ground) to substitute the on board DC to
DC Converter and see if that solves the problem.
The converter is made by a company called Caritronics. Never heard
of them. I'll see what google tells me. I don't really need the DC
to DC converter as I never run the thing off of 12 Volts, but I've
thought about it.
Thanks,
Burt, K6OQK
>Date: Thu, 10 Jan 2013 10:48:38 -0800
>From: Ed Breya <eb at telight.com>
>
>Subject: Re: [time-nuts] Vectron GPSDO Oscillator stranges...
>
>
>Can you completely swap the Vectron crystal oscillator modules between
>the Datum units? Maybe the fault lies in the other part. If they are
>GPSDOs, each must have a DAC somewhere driving the tuning control line
>to the VCXO, The 10 kHz may be the DAC serial data rate, or a PWM rate
>for fine tuning. A fault in that area could cause the sidebands. Maybe
>you really did hear "data." If you can hang a fairly large (several uF
>or more) plastic capacitor on the tuning line without causing the whole
>thing to oscillate, you may be able to observe a decrease in the
>sideband amplitude - a sure indicator that the tuning signal carries the
>problem.
>
>Ed
>
>
>Oops - regarding that capacitance test on the tuning line, I meant to
>say "up to several uF or more." You can start small to see if there's
>any effect. It all depends on the impedance of the tuning line
>circuitry, and the existing amount of filtering - you may need quite a
>bit of C to swamp it out and show a noticeable effect. You're not
>looking for necessarily "normal" or perfectly-settled operation under
>the test condition, just the relative effect on the sidebands.
>
>Ed
>
Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California U.S.A.
biwa at att.net
www.biwa.cc
K6OQK
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