[time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A, Z3811A, Z3812...

GandalfG8 at aol.com GandalfG8 at aol.com
Sat Nov 1 13:14:08 EDT 2014

I've confirmed from the model number that the GPS module on these is indeed 
 an Oncore UT+.
There's a Synergy engineering note available regarding Oncore battery  
backup, and one place a copy can be found is here...
If so desired, it would be possible to retrospectively convert  the UT+ on 
the Z3811A to take the usual rechargeable battery but the  precautions 
mentioned in the engineering note would need to be  implemented.
I'm running file checks on my archives right now so can't confirm  exactly 
what's involved, but I think there's one zero  ohm SMD chip to be removed at 
least, and fitting a battery can of  course bring its own issues.
If anyone's interested, I've just uploaded some detailed photos  of the of 
RFTG-U Ref-1 circuit board to Didier's manuals site.
Probably far more detail there than even the nuttiest of us might consider  
to be sane or healthy but I've got it apart anyway so what the  heck....
and they might come in very useful if it decides to self  destruct whilst 
I'm poking it about on the bench:-)
In a message dated 01/11/2014 06:20:00 GMT Standard Time, bob at evoria.net  

Hi Bob  et al,
I don't understand the direction this question about the supercap  has 
taken.  It's connected to pin 1 of the GPS receiver.  It looks  to be a UT+, so 
that's the battery backup power.  According to my UT+  manual the current 
draw on this pin is between 5uA (at 2.5V) and 100uA (at  5V)?  How many hours 
will a .022F supercap keep at least 2.5V at that  sort of discharge rate?  
Unless the cap has gone bad, it seems more  likely that Bob's comment about 
it doing a fast survey and then doing a slower  one in the background 
probably has merit.  In fact, my unit goes through  its survey mode pretty quickly 
on power up.  So do those current/voltage  figures imply several hours on 
the cap?

From: Bob Camp <kb8tq at n1k.org>
To: Discussion of precise time and  frequency measurement 
<time-nuts at febo.com> 
Sent: Friday, October 31,  2014 9:22 PM
Subject: Re: [time-nuts] Lucent KS-24361, HP/Symmetricom  Z3809A, Z3810A, 
Z3811A, Z3812A GPSDO system


I  sort of doubt that a GPS aux supply is quite that low current. I have 
seen  some RTC’s that won’t last a month on a coin cell. My recollection is 
that the  Oncore backup is closer to that category than the “many years on a 
cap”  group.


> On Oct 31, 2014, at 9:26 PM, Brooke Clarke  <brooke at pacific.net> wrote:
> Hi Bob:
>  When HP came out with the 300 series Rocky Mountain Basic computers they 
were  fitted with a super cap to power the RTC.
> I will keep time for some  months.
> http://www.prc68.com/I/HPIB.shtml#300
>  Mail_Attachment --
> Have Fun,
> Brooke Clarke
>  http://www.PRC68.com
>  http://www.end2partygovernment.com/2012Issues.html
>  http://www.prc68.com/I/DietNutrition.html
> Bob Camp wrote:
>>  Hi
>> The ultra cap is a pretty small one (physical  small). You might be able 
to find a larger (more farads) one that would fit in  the same space. It’s 
not going to help for a hours and hours sort of outage.  It might get you 
from dying in 15 minutes to dying in a half hour.
>> Bob

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