[time-nuts] FE-5680A sweep range setting

Paul Berger phb.hfx at gmail.com
Mon Feb 24 13:14:20 EST 2014


A couple further observations, to make life easier when adjusting C245 
you can unplug the top card and move it aside, the CVXO will lock 
without it, but you will not have the 10MHz to monitor, but you can 
monitor the CVXO output instead.  On the 6 pin connector you will see a 
1 near the outer long edge of the second card, the CVXO output appears 
on pin 5 of this connector and on mine, it locks at 50.25505808 MHz 
according to my 5335A.   I also noted that when the 5680A is well warmed 
up it sweeps through a much smaller range.

It would appear that the one I had trouble getting to lock has some 
secondary issue.  I can get it to lock playing with C245 but the when I 
power off and back on it seems the  CVXO does not start properly 
measured frequency is low and outputs a very weak signal, injecting some 
capacitance by touching a metal screwdriver to the end of one capacitor 
gets it going and once that happens it will lock pretty quickly.... more 
investigation needed.

Paul.


On 2/23/14 6:01 PM, Simon Lyons wrote:
> OK ... I have C245 on the middle board, same as you. Tweaking it and ...
>
> Hmmm, it does affect the range (twitchy is an understatement!) but 
> still no lock. To be continued....
>
> Now by the 'frequency control board' do you mean the board that 
> overlaps the top of the D-Sub connector? I have been at a loss to 
> understand this section. There is all sorts of silicon on it but no 
> inputs of any kind. Just a 5V supply and a single analog output of 
> 1.99V on the orange wire. I'm baffled, so if you know what this board 
> is doing, please tell!
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