[time-nuts] 15 volt power supply for FE-5680A on eBay

Peter Bell bell.peter at gmail.com
Wed Jan 18 20:47:36 EST 2012


One of the regulators (the one that runs the lamp and lamp heater) is
running at 13.8V and has a 500mV dropout voltage, so there is very
little (~ 700mV) headroom. The one that runs the cell heater is about
a volt lower and the one that runs the analog circuits is set to 8.8V,
so has plenty of headroom.

I suspect the lamp regulator is mostly there to reduce the start-up
current, though - the FE-5650 has a very similar lamp circuit with no
regulator and the only significant difference seems to be that the
current pulled when the unit is cold is higher.

Regards,

Pete Bell


On Thu, Jan 19, 2012 at 8:19 AM, paul swed <paulswedb at gmail.com> wrote:
> I think it is important. The specs say 15-18V.
> So I would not drop below the spec. Though interestingly pretty much
> everything inside the system is using switching supplies so perhaps there
> is more room.
> The gtood thing about the switchers is that as the input V goes up current
> should go down if that helps you.
> Regards
> Paul.
>
> On Wed, Jan 18, 2012 at 6:25 PM, Chris Albertson
> <albertson.chris at gmail.com>wrote:
>
>> I used a variable voltage bench supply to experiment.  tried low
>> voltage like you are seeing on my FE5680 and I never got a lock.   The
>> FE5680A spec sheet says 15 to 18 volts and I think you can get buy
>> with 14.5V.  i tried 12.5 and got "nothing"
>>
>> I did not test to find the "breaking point"  But 1/2 volt low was OK
>> and 2.5V low was not ok.
>>
>> What I bought is a 15V open frame supply from allelectronics.com for
>> $11.50.  It turned out to be a very high quality power supply (Digikey
>> has the same unit for almost $40)   This PS does not drop volts even
>> with the line input and load  well out of spec (I tested 63VAC input
>> to a 4A load briefly)  I added an RF "hash" filter "just because I
>> could"  and then an LM7805 and I think I'm OK.
>>
>> I thought about making a linear supply for the cleanest power but i
>> intend to run this 24x7 and don't like wasting so much power.
>>
>> This is the one I bought
>>
>> http://www.allelectronics.com/make-a-store/item/PS-152/15VDC-2.7A-POWER-SUPPLY/1.html
>>
>>
>> On Wed, Jan 18, 2012 at 3:05 PM, Paul F. Sehorne <paul at sehorne.org> wrote:
>> > How important is the 15vdc at the initial startup 2amp, and then how
>> > important at the .7 amp settled rate?
>> >
>> > I just received two of these
>> > http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=280439877318
>> >
>> > Unloaded voltage is ~15.5vdc.  At 700 ma voltage drops to 14.3 volts and
>> > with 2 amp load drops to 13.3 volts with a 2 amp load (and to 10 volts
>> with
>> > a 5 amp load).  Supposedly rated at 6 amps.  I have only checked one,
>> have
>> > not broken the packaging on the second one assuming its performance will
>> be
>> > similar.
>> >
>> > Will this be a problem?
>> >
>> > Paul
>> >
>> > _______________________________________________
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>>
>>
>>
>> --
>>
>> Chris Albertson
>> Redondo Beach, California
>>
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