[time-nuts] FE-5680A Voltage tolerance

Peter Gottlieb nerd at verizon.net
Fri Jan 20 07:42:35 EST 2012


It is not surprising that many of these units work alright below their specified 
voltage.  I would imagine that the internal regulators, in addition to dropping 
voltage, are also there to keep voltages stable, and thus help with unit 
stability.  So, a unit may work fine, and be able to meet stability specs, when 
operated slightly below the 15 volts, PROVIDED that that lower input voltage is 
provided by a stable, regulated supply.  If I were the manufacturer, I would not 
want to have to rely on the supply being perfect, I would want to do my own 
regulation as they have.  These are used in a system where the power supply 
drives many items and there are voltage drops due to wiring, backplanes, traces, 
etc as well as variations due to load changes.  You may be able to have one unit 
work fine slightly below spec'd voltage, but if you do that in a system or with 
an unregulated supply and all bets are off.  Give the unit decent power within 
its specified input range and then that's one thing you don't have to worry 
about further.

Peter


On 1/20/2012 6:09 AM, Rob Kimberley wrote:
> I've had one of mine running on a bench supply for about 2 days now. Have
> just tried turning the voltage down, and things started to get unstable at
> around 12.5V. It didn't drop out of lock however until about 9V.
>
> Rob Kimberley
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Peter Gottlieb
> Sent: 20 January 2012 04:16
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] FE-5680A Voltage tolerance
>
> When I got my first unit I hooked it up to my protoboard power supply which
> is rated at 15 volts 0.5 amps and 5 volts 1 amp.  I was annoyed that it took
> about
> 10 minutes to lock up until I realized the 15 volt supply was down near 11.5
> volts.  Oops.  Substituting my small B&K bench supply (good for up to 3
> amps) resulted in a lock in under a couple of minutes.  Perhaps my unit's
> internal adjustments are still just about right.  It would be nice to get
> the alignment procedure for the thing, but I suppose, fat chance of that.
>
> Peter
>
>
> On 1/19/2012 6:45 PM, gonzo . wrote:
>> Experiment for the day.
>> I thought I'd follow Dons quote and see how tolerant my unit is.
>> My benchmark is at 15.5V it locks in about 3min.
>> I backed off the supply to 10.8V and the lock time (from cold) is 8min.
>>
>> I thought this was interesting given several people report they are unable
> to get a lock when running lower voltage.
>> ian
>>    		 	   		
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