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 <[email protected]>
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.
[email protected]
www.biwa.cc
K6OQK
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