[time-nuts] HP 10811

[ws at Yahoo]

The 10811 units I've measured use slightly different circuits for their
internal ovens.
The single version has a 10V internal regulator for it's temperature
controller, the Dual unit has a 5 V reg. The thermistor bridge voltage is 5
volts on both units.
The standard unit's oven start to come out of regulation at around 16V, the
Dual oven at around 10 volts. For best control I run them minimum at a few
volts above those values. I think the min spec is something like 20V on the
single and 12V on the dual oven units. 
So On the dual oven units, The inner, outer and Osc can all be run from 12V.
But if you want nut performance, best not to use the same supply for them. 
I start with a 15V supply, so that there is no interaction between circuits.

ws


*****************
From: Richard (Rick) Subject: Re: [time-nuts] HP 10811

On 2/11/2016 2:56 PM, ws at Yahoo via time-nuts wrote:
> Joe
>
> The inner oven voltage needs to be stable! To better than 0.1V.
> Unlike the single oven unit, the inner oven on the dual oven unit runs
fine
> at 15 Volts. It draws a couple hundred ma after warm-up.
>

It's been a long time, but IIRC, it was common knowledge
within HP that the standard 10811 oven will run on 15 Volts,
but it just takes longer to warm up.  The most extreme
example was the 5334A, which had such a bogus power supply
design that the voltage sagged to +12V during warmup.
Now the oven won't work correctly on only 12V, but it
will work to the extent that it warms itself up.  Once
the current cuts back, the voltage goes back up to over
15V and it works fine.  When I started the 5334B project,
the power supply was the first thing to get redesigned.

Rick N6RK