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

Bob Camp kb8tq at n1k.org
Tue Mar 22 07:37:54 EDT 2016


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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