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

John Beale beale at bealecorner.com
Wed Nov 30 07:17:43 UTC 2011


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#5680473663653140162

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/0WRM10pGG0Kd89Ji80yoa9MTjNZETYmyPJy0liipFm0?feat=directlink

thanks for any advice!

John Beale
N8JUF



More information about the time-nuts mailing list