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

Peter Bell bell.peter at gmail.com
Thu Jan 12 03:22:35 UTC 2012


Hi, Ignacio

OK, the photo that shows the 'AC161 is here:

http://ka7oei.com/FE-5680A-top-jumper_1a.jpg

None of the units I've opened have these parts in them.

As far as I can see, the only places the 5V feeds are the 'AC240 and
that Maxim regulator - the 3.3V rail runs basically all the digital
circuitry in the unit, but if it's locking up, then it's reasonable to
assume that all that stuff is working since it's all rather critical
to the unit's operation.

Regards,

Pete


On Thu, Jan 12, 2012 at 9:23 AM, EB4APL <eb4apl at cembreros.jazztel.es> wrote:
> 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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