[time-nuts] Subject: Subject: Re: HP5065A C-field current voltage mod

[Chuck Harris]

Are you sure?  Perry was proposing to use a TL431 to
make an oven, using its famous temperature sensitivity,
and inside the oven would be another TL431 that acted
as a voltage reference.

Every oven I have ever seen that is temperature controlled
has a part that is quite good at measuring temperature at
the helm.

-Chuck Harris

Poul-Henning Kamp wrote:
> --------
> In message <1530394039.1439027.1441348869239.JavaMail.yahoo at mail.yahoo.com>, Pe
> rry Sandeen writes:
>
>> OK, but why?  The temperature would be stable so the resistorsand
>> reference diode wouldn't drift.
>
> No, the temperature is not stable, not even close.
>
> Given that the TL431 is quite good at measuring temperature, that
> makes it unsuitable in this case.
>
> I have identified one source of the temperature fluctuations:  The
> series pass transistor of the +20V rail is located right beneath
> the A15 PCB, so any variation in mains (or EXT DC) voltage causes
> the A15 temperature to change accordingly.
>
> More details here:
>
> 	http://phk.freebsd.dk/hacks/HP5065A/20150903_psu/
>
>