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

EB4APL eb4apl at cembreros.jazztel.es
Thu Jan 12 02:23:00 UTC 2012


Hi,

I'm interested in seen those photos, because I collected a bunch of then 
from various owners but I dont see this 'AC161 even on in the switching 
regulator pair.
I made a goof the other day when I connected the 5 V input to a 15 V 
power supply and toasted the 'ACT240 buffer which drives the lock 
indicator and the PPS outputs.  I know that the 5 V is used to generate 
the +3.3 V in an internal regulator and because I'm not sure what else 
is toasted I want to trace this voltage and see if it is ok.  The unit 
is mostly working, it locks and also generates the 1PPS, measured at the 
input pin of the buffer, but I want to check everything that can be 
damaged and replace the failed parts.
So I'll benefit from partial schematics, parts location and 
identifications and all the like. Please share the info that you have.

Best regards,
Ignacio, EB4APL


On 11/01/2012 19:22, Peter Bell wrote:
> 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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