19 Apr
2006
19 Apr
'06
6:55 a.m.
Sat, 15 Apr 2006, "Bruce Lane" <kyrrin at bluefeathertech.com> wrote:
My thanks to all who offered assistance on my
issues with the 'tech
special' Trak Systems 8820 GPS station clock. The unit was successfully
repaired, and has been working for nearly a full week without any
further signs of problems.
For the curious: The problem turned out to be that one of the
firmware EPROMs developed a broken internal bond wire on the output-
enable lead. This caused the chip to appear completely blank to both the
Unisite programmer and the Trak device. My contact at Trak was kind
enough to send over image files to do a fresh set of EPROMs.
The only other adjustment I found myself making was a fine-tune
alignment on the 10MHz ovenized oscillator, to bring its center
frequency back to a point where the reference circuitry could discipline
it down to full accuracy. That was also accomplished without incident,
and I now have a second Stratum-1 level clock and frequency standard for
my lab.
The moral of the story: EPROMs can fail too! Just not in the way we
might expect. ;-)
Congratulations to getting this thing back into functional state. I wish you
a good time and many years of satisfying operation for your device.
Incidentally, I've been having a bit of fun with a MEINBERG GPS166 Satellite
Controlled Clock lately - it had been set aside as defective at the
computing center of Erlangen University and I happened to get it for the
asking, together with its bullet-shaped "radome" antenna/amplifier.
When I finally built myself a coaxial cable to connect the two (SMA <->
N-Type), I had a working setup! But after a relocation a bit later, I got
some smelly smoke and an "antenna fault" error when I powered it on. Turned
out to be a small cylindrical choke in the shielded RF box which had gone
open circuit - possibly involved with supplying power to the antenna
amplifier.
I checked the coaxial cable for shorts, couldn't find one at that time,
replaced the choke and had the next one burn through. I disassembled and
reassembled the N connector very carefully, replaced the choke once again
and have been operating the clock without problems since then. It too can
give out fixed and adjustable frequency pulses - along with second and
minute signals, which you could amplify adequately to drive daughter clocks
like that falling-leaf wall clock I have (needs a 24V pulse every minute).
The special plus of the unit I have is the so-called "Erlangener Firmware"
which was custom-written for Erlangen University. The usual variety only
used the serial port for giving the time - either in intervals, when a ? was
entered or when a pulse occurred on a logic input - but this one also puts
out the geographical location, so one could even use it for a navigation
system, in theory at least.
So long,
--
Arno Kletzander
Stud. Hilfskraft Informatik Sammlung Erlangen
www.iser.uni-erlangen.de
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