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.
Any guidance would be appreciated.
Thanks,
Burt
Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California U.S.A.
b...@att.net
www.biwa.cc
K6OQK
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