[time-nuts] Not Vectron GPSDO Oscillator stranges...

Burt I. Weiner biwa at att.net
Sun Jan 13 07:11:52 UTC 2013


SATURDAY EVENING
Gang,

More update and good news...  I removed the Caritronics switcher 
supply module and connected the Cisco ADP-30RB supply in its 
place.  I'm pleased to announce that my DATUM 9390 is happy.  The 
power supply noise is less than 5 mV on all three rails under 
load.  I'm letting him cook and after about 8 hours he's presently 
locked at 6E-12.  The 10 kHz sidebands are gone or at least 80 dB 
below the 10 MHz signal and the Cisco power supply is only a tad 
above ambient temperature.

I found that a Molex 6 pin male will mate with the connector on the 
end of the Cisco power supply cable.  It's possible to plug the 
connector in, but rotated 180 degrees, so that's of concern.  I'm 
looking at a few options to change the connector for positive 
keying.  I'm also concerned about any future problems causing the 
Cisco supply to spike and do some serious damage.  I may add a 
crowbar preceeded by a fuse on each of the 3 rails.  Maybe I'm being 
over cautious, but having once lost the mother board on my HP-3336A, 
I'm a bit nervous.

Anyway, I wanted to let the gang know what has transpired.  I'll let 
you know what I do about the connector.

Burt, K6OQK


FRIDAY EVENING
Gang,

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.  Stu 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 saw 
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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