[time-nuts] LPRO-101 BITE (~lock) Signal Always Low

iovane at inwind.it iovane at inwind.it
Tue Mar 22 11:43:41 EDT 2016


Wayne,

are you sure your LPRO actually locks? You say you have measured 10.000 MHz 
but you don't mention the other decimals. Some years ago I characterized some 
LPROs of mine, and from my notebook I take that, on one sample for instance, 
prior to lock the frequency swept up and down between (about) 9.999860 and 
10.000230. Such a span was rather typical among units. A faulty unit of mine 
remained stuck at the upper limit without reversing the sweep. This was due to 
a faulty resistor in one of the two (upper) voltage comparator circuits. Anyway 
I don't know if this would affect the BITE, but I suggest you to check the 
other decimals.

Antonio I8IOV 

>
>The BITE signal is the only way to to know if it has a lock...
>
>Wayne
>
>> On Mar 22, 2016, at 4:37 AM, Bob Camp <kb8tq at n1k.org> wrote:
>> 
>> Hi
>> 
>> There are probably a dozen or more things that contribute to the BITE 
output. It could be
>> a regulator out of range. It also could be the VCXO nearing tune limit. If 
the unit locks up and
>> seems to work, I’d ignore it and move on.
>> 
>> Bob
>> 
>>> On Mar 21, 2016, at 9:42 PM, Wayne Holder <wayne.holder at gmail.com> wrote:
>>> 
>>> I have a surplus LPRO-101 that seems to power up OK.  The power draw 
starts
>>> at 1.7 Amps and then, after a few minutes, drops down to 600 mA, or so 
and,
>>> after this startup, the output shows a 10.000 MHz signal thats 's
>>> accurately as I can measure it.  The lamp voltage is 6.2 volts, which 
seems
>>> within spec.  However, the BITE signal that's supposed to indicate lock
>>> with a LOW level is always LOW and never changes.  The docs say that BITE
>>> signal should start at a HIGH level to indicate no lock and then drop to a
>>> LOW when lock is obtained.  So, this behavior seems all wrong.
>>> 
>>> I opened the case and observed the purple glow of the lamp and probed
>>> around IC U401, which buffers the BITE signal, and saw the same signal LOW
>>> level.  U401 is getting 5 volt power and the inputs to the AND gate used 
as
>>> a buffer for the BITE signal match what I'd expect.  But, lacking a proper
>>> schematic, I'm not sure how to trace this back to the problem.  Has anyone
>>> ever seen a symptom like this with an LPRO101?
>>> 
>>> Wayne


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