[time-nuts] Z3801 EFC error

[J. L. Trantham]

Bob,

The thermal fuse is inside the OCXO which is inside the outer oven.  There
was a recent (past week or so) thread on this list about a thermal fuse
failure including pictures of the inside where the fuse is located.  This,
however, was for the 'non' wrapped version of the 10811.  The problem will
be getting past the outer oven.  I've never tried that though I have
replaced the thermal fuse on the 'non' wrapped 10811.  That was really
straight forward.

I don't recall seeing a manual specifically for the 'wrapped' version of the
10811 but the manual for the 'non' wrapped version is available on the
internet.  I think one is on Didier's site.

The trouble shooting guide is very helpful in finding out if the thermal
fuse is the problem.  Just measure the heater circuit current for the inner
oven.  If zero, the thermal fuse is the place to start.  The outer oven,
though, I think is separate.  If your Z3801A is used indoors, I suspect the
outer oven is probably not needed.

Good luck.

Joe


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Robert Benward
Sent: Tuesday, November 01, 2011 8:00 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Z3801 EFC error

Joe,
Good guess.  It's a 10811 with an additional oven wrapped around it for 
better thermal control.  I'll check it in a couple days when I get home.  Is

this thermal fuse on the outside?

Anyone have a schematic of this unit?

Bob

----- Original Message ----- 
From: "J. L. Trantham" <jltran at att.net>
To: "'Discussion of precise time and frequency measurement'" 
<time-nuts at febo.com>
Sent: Tuesday, November 01, 2011 12:21 AM
Subject: Re: [time-nuts] Z3801 EFC error


>I think it uses a 10811 OCXO.  See if it is warm.  If not, perhaps the
> 'thermal fuse'?
>
> Joe
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Bob
> Sent: Monday, October 31, 2011 11:17 PM
> To: time-nuts at febo.com
> Subject: [time-nuts] Z3801 EFC error
>
> Hi,
> My Z3801 just crapped out.  It seems that the DAC has ramped up to the
> rails, 1048560, and I'm getting an EFC fault.  Any tips before I open the
> unit and start poking around?  The oscillator is running and pretty close 
> to
> 10MHz, I don't have any reference accurate enough to check it.  Any trends
> here, is it the EFC in the oscillator or is it the DAC and following
> amplifiers?
>
> Thanks, Bob
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