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

Wayne (gmail) wayne.holder at gmail.com
Tue Mar 22 08:43:53 EDT 2016


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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