[time-nuts] How I got my FE-5680A to lock in Sydney, Australia

[Ed Palmer]

Hi Jim,

This behaviour reinforces my thought that there's something physically 
wrong inside the unit.  I'd be tapping it with the plastic handle of my 
screwdriver while I rotated it to see if it would lose lock.

Think of it this way:  Do you want to fix it now or have it fail again 
in a few months when you're using it for something important?

Ed

On 2/9/2014 6:39 PM, Jamieson (Jim) Rowe wrote:
> Hi again Magnus, Mark, Tom Harris, Ed Palmer et al,
>
> Well, before performing any surgery on my tricky little beasty, I 
> decided to check its frequency swing limits when starting up in the 
> 'inverted' position, and then when starting up in the right-side-up 
> position. Here's what I found, as before looking at the frequency with 
> my counter (GPSDXO 1pps timebase):
>
> Inverted position:  swings between 9,999,798Hz and 10,000,001Hz, 
> before locking.
> Normal position:   swings between 9,999,756Hz and 10,000,057Hz, a few 
> times.
>
> But wait for it -- it then locked up, reliably, in the right-side-up 
> position!
>
> So now I'm really confused. It looks as if whatever was wrong with it 
> before has somehow fixed itself, after running it for a couple of days 
> locked in the inverted position...
>
> Anyway, I think I'll leave opening it up for a while (at least) -- 
> since it's now running locked fine in the right-side-up position. I 
> don't want to tempt fate, while its OK.  What's that old adage? If it 
> ain't broke, don't try to fix it.
>
> Cheers all,
>
> Jim Rowe
>
>
> -----Original Message----- From: Jamieson (Jim) Rowe
> Sent: Monday, February 10, 2014 8:05 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, 
> Australia
>
> Hi Magnus,
>
> Thanks for your further comments. As you probably saw in my reply to Mark
> Sims, I am proposing
> to check the swing limits 'before and after' inverting the unit, to check
> out the theory before I open it up and try tweaking C217.
>
> Cheers,
>
> Jim
>
>
> -----Original Message----- From: Magnus Danielson
> Sent: Sunday, February 09, 2014 7:34 PM
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, 
> Australia
>
> On 09/02/14 02:57, Jamieson (Jim) Rowe wrote:
>> Hi Magnus,
>>
>> Thanks again for those further suggestions. I do have a GPSDO, and I had
>> been able to use it with a counter to check that the FE-5680A was
>> swinging either side of 10MHz. But I didn't make sure that it was
>> swinging evenly each side of 10MHz . According to my notes it was
>> swinging between  9.999770 and 10.000036MHz -- i.e., about 230Hz low and
>> about 36Hz high. But it was spending more of the time below 10MHz than
>> above -- does this suggest to you that I should tweak C217 until it
>> swings by about the same amount either way?
>
> Yes, that is exactly what I would do.
>
> Cheers,
> Magnus
>
>
>