[time-nuts] FE-5680A PPS on pin 6 (or not)

beale beale at bealecorner.com
Wed Jan 11 17:54:11 UTC 2012


All three of my FE-5680A units show a constant DC voltage on pin 6, with absolutely no PPS signal. This is when pin 3 is low (lock) and the 10 MHz output is indeed locked at 10 MHz (within 4E-10 anyway).  I am using a Tek TDS-210 digital scope which certainly has no problem with a 1 usec pulse, and in fact, I did see a nice square 1 usec pulse on Pin 6 once, from one unit. But it went away after a power cycle, and did not return.  I know many (most?) people do see the 1 PPS so perhaps all three of my units are damaged (?)

I presume the 1 PPS signal would come from the XC9572 CPLD which also drives the 10 MHz signal, so I'll try tracing back which pin that is.  I labelled a few CPLD pins already (60 MHz in, 30 MHz and 10 MHz out) here:
https://picasaweb.google.com/lh/photo/dUtTwuNnP-y2nL-wR84ELNMTjNZETYmyPJy0liipFm0


>  -------Original Message-------
>  From: Chris Albertson <albertson.chris at gmail.com>
>  To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
>  Subject: Re: [time-nuts] FE-5680A arrived
>  Sent: 11 Jan '12 08:37
>  
>  On Tue, Jan 10, 2012 at 10:11 PM, Joseph Gray <jgray at zianet.com> wrote:
>  > I'm not seeing a PPS on either of these. All I see is about 17 mV P-P
>  > of noise that looks like a multi-stepped sine wave. I'm using a TDS
>  > 340 scope.





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