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

Jamieson (Jim) Rowe jimrowe at optusnet.com.au
Sun Dec 15 15:25:30 EST 2013


Hi Ignacio,

Thanks for that information, too. I will try moving the tuning trimmer a bit 
in both directions, 'just in case'. But if I still can't get it to lock, I 
think that will mean that the problem is somewhere else - perhaps in the 
photodetector?

Regards, and best wishes for the festive season.

Jim Rowe


-----Original Message----- 
From: EB4APL
Sent: Sunday, December 15, 2013 12:32 PM
To: time-nuts at febo.com
Subject: Re: [time-nuts] Schematic for the 'analog' section of an FE-5680A?

Jim,

I also found my notes for other unit.  It sweeps from 9.9997414 to
10.0000493 and also locks in 3 minutes.

Regards,
Ignacio EB4APL



On 15/12/2013 2:26, EB4APL wrote:
> 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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