azelio.boriani at screen.it
Sat Mar 17 14:18:36 UTC 2012
Wow, no limits on the reverse engineering capabilities of this group...
amazing, now where is Elio? He must be interested in this. [I have no
FE5680A but followed the heavy posting about it, I prefer the LPFRS Rb]
On Sat, Mar 17, 2012 at 2:12 PM, J. L. Trantham <jltran at att.net> wrote:
> I would love to have a set of the pictures.
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Rich
> Sent: Friday, March 16, 2012 3:05 PM
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] FE5680A
> This is my first post here. Unfortunately I found this informative group a
> bit late.
> I got from e-bay a similar unit to yours with an identical pin-out from the
> e-bay listing. As in your case I did not get a 1pps output and there were
> lock indication although the 10MHz initially wandered and after 5 min or so
> it locked.
> I opened to unit and traced a good part of the circuit with the aid of
> 25 high resolution x-rays of the board. I mounted them on a wall in my
> workshop and created a composite high def x-ray about a yard across. This
> excellent to follow traces below the ICs and in the board layers and vias.
> Don't know if I can post attachment but I'll try one to give you the idea
> with a jpg of the layout. Should people be interested I can post all of the
> 25-30 x-rays of the pc board on a website for those who would like to trace
> or troubleshoot the overall circuit without having to remove the chips.
> Finally found the Fairchild 74ACT240 to be the culprit. It was pulling down
> the lock circuit and preventing the 1pps from coming out. Seller must have
> damaged it and that is why it was at a such low price I guess.
> I now use a 330 ohm resistor in series with a LED and the lock indicator
> work fine and well as the 1pps.
> As to the RS-232 I get a response using 960 n 8 1 as outlined in these
> forums. Did not dare changing the frequency yet until I get a higher
> precision setup that will actually measure the change. No quite there yet.
> Hope this is useful for some of the members.
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