One thing you also should do is set the tuning, even if it sweeps
through 10 MHz if outside the lock range it will not lock. I have
seen it.
Bert
Sent from Samsung tablet"Jamieson (Jim) Rowe"
<jimr...@optusnet.com.au> wrote:Hi Bert,
Thank you too for your tips and suggestions. I thought there might be
'some'
analog circuitry in the 5680A, because the photodetector output from the
'far end' of the Rb resonance cavity probably needs some amplification,
before its 'strong enough' to be fed into an A-to-D converter. In any
case
the schematic I found in the time-nuts archive doesn't seem to include
anything in the 'physics package' -- the Rb lamp oscillator, the
microwave
oscillator feeding the resonance cavity, the photodetector and its
output
amplifier or whatever. So it looks as if I'm going to have to search
around
in that area myself...
Anyway Bert, thanks again and all the best for the festive season.
Jim Rowe
Sydney, Australia
-----Original Message-----
From: ewkeh...@aol.com
Sent: Saturday, December 14, 2013 12:49 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Schematic for the 'analog' section of an
FE-5680A?
Jim
unlike older Rb's there is very little analog in the unit. It is
sweeping
trough its lock range so maybe you may find something around the
lamp. The
lamp should not be the problem because the 5680 has not been around and
been operating for extensive time before pulled.
How ever I like to caution time nuts and be careful who they buy from, I
did have a bad experience with one vendor and I did post it previously.
False claim of new and when returned after return authorization refused
refund
since I refused to give a 5 star rating. I forwarded the emails to
ebay and
they did nothing. So any time nut that buys from ggg* fitting deserves
what he is getting. We have other sources out there that time nuts have
good
experiences with and with the price increasing by a factor of 4 one
should
be careful. Personally I do not think they are worse the price
Bert Kehren Miami
In a message dated 12/12/2013 4:30:57 P.M. Eastern Standard Time,
jimr...@optusnet.com.au writes:
Hi,
I’m an elderly time-nut newby, and I’ve already struck trouble with a
used FE-5680 Rb-vapour reference
I bought via eBay. It runs (from +16V and +5V), and the current drain
starts at 1.75A and then drops over
5 minutes or so down to about 650mA. But it won’t lock, even if I
leave it
powered up for a few hours (with a fan
to keep it from getting too hot).
The output frequency just keeps switching up and down between about
9999850Hz and 10000080Hz, with a bit of ‘lingering’
near each end. And of course the ‘lock’ output at pin 3 stays
stubbornly
at about 4.35V.
To my newby brain, this sounds like the problem is either in the Rb
lamp
(too dark, perhaps), or
else in the photodetector and buffer, etc, forming the ‘dip detector’
part of the feedback loop.
Could one of you much-more-experienced time-nutters tell me if my
diagnosis sounds right?
Also, I’ve found a schematic for the digital sections of the
FE-5680A in
your archives, kindly drawn up
by one of your very experienced members, but has anyone done a similar
schematic for the ‘analog’
sections? I suspect I’m going to have to work out for myself where to
test for a fault in these
sections. There’s also a bit of a mystery (in my mind, at least)
regarding
that little 2-pin SIL header
just near the Rb lamp, on the top of the PCB. Anyone know what that’s
for?
All the best in anticipation, folks.
Jim Rowe
