[time-nuts] troubleshooting a FE-5680A (got two; only one works)

[Bob Camp]

Hi

At this point I'd contact the seller. You know that the part has a problem
and you have done enough checking to be sure it's nothing trivial (like a
loose wire). The worst that can happen is he does not reply, the best is
that he sends you another part for free. There are a number of possibilities
in-between the two. At this point you have a pretty good case. Once you
start twiddling this or that, you are not in as good a position.

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of John Beale
Sent: Wednesday, November 30, 2011 2:18 AM
To: time-nuts at febo.com
Subject: [time-nuts] troubleshooting a FE-5680A (got two; only one works)

Just yesterday I received two FE-5680A units from China.  One of them works 
and one doesn't achieve lock. Both are labelled with FEI P/N 
217400-30352-1. Here's a photo of the one that works, the other looks just 
the same but different serial number.
https://picasaweb.google.com/109928236040342205185/FE5680A#56804736636531401
62

FE-5680A Rb #1:
At startup, RF out (pin 7) ramps from 9.999828 to 10.000066 MHz for a few 
minutes, then locks at 10.000000 MHz and pin 3 drops low.  The RF signal is 
about 2 Vpp.  Power draw at startup about 25 W, dropping to 10 W.

FE-5680A Rb #2:
RF out scans from 9.999799 to 9.999994 MHz repeatedly, and does not achieve 
lock. Pin 3 remains high.  The RF signal is about 1 Vpp (half the level of 
the working unit).  Power draw similar to unit #1.

Any suggestions for what might be done to prod the 2nd unit towards 
working?   I see some things which might be trimmer caps on the board, and 
what might be a round heating element(?) soldered to a crystal can in this 
photo: 
https://picasaweb.google.com/lh/photo/0WRM10pGG0Kd89Ji80yoa9MTjNZETYmyPJy0li
ipFm0?feat=directlink

thanks for any advice!

John Beale
N8JUF

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