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" <[email protected]> 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: [email protected] Sent: Saturday, December 14, 2013 12:49 AM To: [email protected] 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, [email protected] 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 _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
