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

Peter Bell bell.peter at gmail.com
Wed Jan 11 18:22:14 UTC 2012


You can put me in the "No 1 PPS on pin 6" camp, too - I made extensive
attempts to detect it on the first couple of units (multiple scopes,
even connecting in to an edge-sensitive interrupt pin) and detected
nothing.  The other units, I just poked a scope (TDS420A) at it, but
could see nothing.

One thing I did notice was that in one of the photos on here (the one
about the 5V switching regulator) there were some components ('AC161
and associated parts) installed on the PCB that were not present on
any of the units I opened. This may be related, or may not - but at
the least it does suggest that despite having the same P/N these units
might not all have the same build spec.

Regards,

Pete Bell

On Thu, Jan 12, 2012 at 12:54 AM, beale <beale at bealecorner.com> wrote:
> 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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