[time-nuts] HP5065A C-field current is temperature sensitive

Poul-Henning Kamp phk at phk.freebsd.dk
Mon Aug 31 02:28:53 EDT 2015

In message <55E39AF2.2050708 at rubidium.dyndns.org>, Magnus Danielson writes:

>Ehm, eh... that transistor pair you have there. How *tight* together is 
>really the transistors thermal connection? I bet not all that good.

They're in the same TO5, but I don't know if they're the same die.

I have about 45-50 microvolt difference between their bases.

>Anyway, the take-away is that you should look at that discrete 
>op-amp and see if it is not causing you the thermal dependence you are 
>trying to locate. Maybe replace it with a more modern op-amp like the 
>741 or something (irony may have been used).

Yes, that is absolutely the plan.

The integrator and AC-amplifier in the HP5065 gets upgraded to 
chip op-amps in later revs, but this one does not.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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