[time-nuts] Z380XA The saga of the aging 10811

[George Atkinson]

Well, if the batch/revision of op-amps had a doping, contamination or
similar issue, the input offset could be drifting fairly constantly causing
a temperature channge in one direction.

Robert G8RPI.

On 9 September 2015 at 04:40, Bob Benward <rbenward at verizon.net> wrote:

> Hi Ed,
> OK, a bad oven.  I can buy that.  But then if the oscillator is constantly
> drifting, would that not imply that the oven is constantly changing
> temperature, in one direction?
>
> BTW, the curve is starting to flatten out.  It might be flat before It gets
> to 1000K counts.
>
> Bob
>
> >>> -----Original Message-----
> >>> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of ed
> >>> breya
> >>> Sent: Tuesday, September 08, 2015 10:55 AM
> >>> To: time-nuts at febo.com
> >>> Subject: Re: [time-nuts] Z380XA The saga of the aging 10811
> >>>
> >>> It could be that the inner oven temperature regulation is off a bit, or
> even
> >>> failed. There was a report at one of the popular time-nuts oriented
> websites (I
> >>> forget which one, but it's the one that had extensive coverage of the
> Z3801A)
> >>> about inner oven problems a few years ago. I took mine apart and found
> that
> >>> it had an IC of a particular date code range that was prone to failure.
> I can't
> >>> recall whether I replaced it with the same type but different date, or
> an
> >>> alternative, but it worked just fine after that, with no tweaking of
> coarse EFC
> >>> needed.
> >>>
> >>> The IC was a dual opamp I think, that controlled the oven temperature
> >>> according to the thermistor signal, and drove the heater transistor(s).
> >>> It was a fairly high performance type, but not that unusual. I think it
> was a
> >>> Linear Technology brand part.
> >>>
> >>> Ed
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