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

[Wayne Holder]

I don't currently have a way to accurately measure the frequency of the
output, but my assumption is that oscillator is running, but not locked.  I
did some more poking around and found that the crystal volts monitor (pin
9) starts low (around 4 volts) and then slowly rises as the unit runs.  It
rises to about 14 volts and then stops.  So, this may be a similar problem
to what you described.  However, lacking proper schematics, I'm not sure
where to look next.

Wayne

On Tue, Mar 22, 2016 at 8:43 AM, iovane--- via time-nuts <time-nuts at febo.com
> wrote:

> 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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