[time-nuts] DATUM 9390-52054 Grief again...

Burt I. Weiner biwa at att.net
Sat Apr 6 18:07:36 EDT 2013


(Note: additional information about the receiver module has been added.)

Burt

Gang,

You will remember several months ago I had some stranges that I 
thought were related to a defective Vectron oscillator in one of my 
DATUM 9390-52054.  That turned out to be a the internal switching 
power supply so I replaced it with an external Cisco unit.  I've done 
this in three units, two are mine and one belongs to Stu, K6YAZ.

Well, I now have a different grief in one of my units.  It had been 
cooking along swell with no problem ever since I replaced the power 
supply.  This morning I notice that one of my units had the lock and 
tracking lights out.  The display said that the signal level was low 
and there were no usable satellites.  The 10 MHz output is also about 
20 or more dB low.  I assumed the power supply is all right because 
the display was working and it said it was 9-E9, not so good, but 
working - sorta.  I swapped antennas and the good Datum was happy so 
I know the antenna is ok.  when I got inside I checked the power 
supply rails and they're within .05 Volts of where they should 
be.  There is 5 Volts on the GPS module and there is 4.96 Volts on 
the antenna Type-N connector (measured with the antenna line 
disconnected.)  Power cycling the DATUM did not resolve the problem.

Does anyone know if the symptoms above will occur if the 10 MHz 
oscillator is defective?  I can understand it not tracking or not 
locked, but could this cause the receiver to not see or indicate any 
satellites?  Since I only have two of these units on line, I'm very 
reluctant to start swapping modules because I would be without any 
working reference, so I need to keep one up and running.  Both of my 
units are on a UPS, and according to the clocks in the kitchen, the 
bedroom, and the old VCR, we've not had a power interruption.

I do not recognize the GPS receiver module, but it has the following 
number on it:  TNL 22880-B.  I have the schematics for the overall 
DATUM 9390-25054, but the GPS module in just a block.  By the way, 
the GPS block on the DATUM overall schematic is marked, "SV6 / 
(TANS)".  I suspect this means something noteworthy.

Any guidance would be appreciated.

Thanks,

Burt

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California  U.S.A.
biwa at att.net
www.biwa.cc
K6OQK  



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