[time-nuts] Schematic for the 'analog' section of an FE-5680A?

[EB4APL]

Jim,

My unit, according to my notes, sweeps between 9.999766 MHz and 
10.000056 MHz and locks in 3 minutes from cold start.  Maybe you have to 
move the frequency a bit towards the low side.

Regards,
Ignacio EB4APL


On 15/12/2013 0:27, ewkehren wrote:
> 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" <jimrowe at 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: EWKehren at aol.com
> Sent: Saturday, December 14, 2013 12:49 AM
> To: time-nuts at 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,
> jimrowe at 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
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