Re: [time-nuts] Looking for Z3801 OCXO

[John Ackermann N8UR]

Thanks, Warren.  That's a very nice solution!  I have a unit on the way from 
another time-nut, so I should be set.

I'm pretty sure the problem with the old unit is just aging as I watched the 
EFC creep for months toward the limit.  I bought two units at the same time 
(long, long ago) and though they had similar running time, this one always had 
EFC values far higher than the other one, which is still running fine.

> On Feb 5, 2016, at 1:39 AM, ws at Yahoo  wrote:
> 
>  
> John
> If it is off very far the first thing I'd suspect is the inner oven.
>  
> Assuming the freq is still stable and low noise, one option is to rewire it, 
> and make the freq adjustment accessible.
> Removing the original inner wiring wrap also provides many other advantages, 
> and no down side that I've found.
> After modifying several, it now takes me about an hour to do.
> From the outside you can not tell that it has been modified, unless I change 
> the crappy little blue shielded RF and EFC cables that it originally comes 
> with, which I now always do.
> It takes about five minutes on a correctly modified unit to readjust the 
> frequency. The adjuster nut and hole is accessible after temporarily removing 
> the bottom outer cover, thru a 3/8 inch access hole drilled in the bottom of 
> the outer oven that is placed *under* the bottom heater flap.
> It is easy to adjust thru the bottom of the unit and can be done without 
> powering down or disturbing the oscillator or either oven's power.
>  
> Picture attached of modified inside cabling, before the two shielded cables 
> are added.
> No mess. Any goo gets cleaned up with alcohol or thrown away.
>  
> ws
>  
>  
> 
> John Posted:
> "Looking for Z3801 OCXO"
>  
> I have a Z3801A whose oscillator has aged out of correction range, and
> thus throws an EFC alarm.
>  
> Anyone have a still-in-range double-oven HP10811 from a unit that died
> for another reason?  If so, I'd be happy to acquire it.
>  
> (I tried disassembling one of the double-oven 10811s years ago and found
> that extracting the oscillator can from the outer oven, heater, and
> gooey insulation made such a mess that it would be impossible to
> reassemble.)
>  
> Thanks!
>  
> John
>  
>  
> 
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Re: [time-nuts] Looking for Z3801 OCXO

[ed breya]

You may have seen this before, but there is a nice writeup on how to 
disassemble the whole thing, with pictures and all.


http://www.realhamradio.com/GPS-oven-journey.htm

I had to take mine apart quite a few years ago to replace the opamp in 
the inner oven temperature regulator circuit. If your problem is just 
adjustment, you don't even have to open the inner oven.


BTW as I recall, the ovens are sequenced, to reduce power at turn-on. I 
forget the order, but one (probably inner) has to be up and running 
close to setpoint, before the other is activated.


Ed
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Re: [time-nuts] 58503A does not track

[claude . ff]

- Mail original -
> De: "Mike Cook" 
> À: "Discussion of precise time and frequency measurement" 
> Envoyé: Jeudi 28 Janvier 2016 11:21:45
> Objet: Re: [time-nuts] 58503A does not track
> 
> 
> > Le 28 janv. 2016 à 07:37, claude...@aliceadsl.fr a écrit :
> > 
> > Thanks for your reply
> > 
> > I don't think it's a computer problem because I can see the GPS is
> > not locked when I compare the 10 MHz output with a Rubidium.
> > By the way, I don't use software but the screen command under
> > Linux.
> > 
> > Maybe the motorola bord is dead, I will investigate this : I have
> > to send commands directly to the board, as suggested by someone
> > offlist.
> > 
> > 
> > The board in the GPSDO is a Motorola 84D43579M03 . The same as this
> > one :
> > http://www.ebay.com/itm/HP-Z3801A-Z3805A-GPS-Module-Motorola-Oncore-P-N-84D43579M03-/161594138402?nma=true=jnWr5n2KQf1WL6JylF%252BMgtIr1%252FM%253D_cvip=true=nc&_trksid=p2047675.l2557
> > 
> > 
> > Do you think it can be replaced by this one :
> > http://www.ebay.com/itm/Z3801A-Z3805A-GPS-Receiver-VP-oncore-B4121Z1116-/281670591394?hash=item4194e023a2
> > 
> > 
> 
> I think you can replace your receiver with this. Some Z3801As ( which
> are pretty much the Telco versions of the 58503A) came with the
> 84D43579M03 part , but mine has a B412P1115 . I think you should be
> safe with the replacement. I have a Motorola document which says
> that the B parts with firmware 8.1 and later have "8 channel code
> added" with some related commands, so I guess your part is a 6
> channel model. In a command reference manual from Synergy Systems,
> Randy Warner states
> 
> “house numbered” receivers with total jibberish for model numbers
> have worked their way into the surplus market, but under the skin
> they are probably pretty standard parts. “If it walks like a VP,
> talks like a VP, and acts like a VP, it’s probably some variation of
> a VP.”
> 
> I can’t see any indication in the command guide that 8 channel
> receivers will not accept the 6 channel command set however that
> might be an issue at set up .
> 
> My advice is suck it and see. The VP above is cheap enough . I am
> going to order one if I can get a shipping price to France and there
> are any left.
> 
> 

Hello,

A little follow-up : I've bougth the card in the link above and it works 
perfectly with my 58503A. 
Thanks to you both for the advices.

Claude
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