[time-nuts] HP 5061A/B Cesium tube conundrum

paul swed paulswedb at gmail.com
Sun Jan 22 20:22:24 EST 2017

Curious if you ever received any other comments or had success?

On Mon, Jan 16, 2017 at 5:07 PM, paul swed <paulswedb at gmail.com> wrote:

> Corby thats a heck of a puzzle. I am trying to think about how you could
> prove it. I have some thoughts that are not at all well formed. It comes
> from my experiments on Frankenstein temp control.
> If you could please tell me what you might expect the alternate bridge
> resistors to be overall I will look through my various bits to see if there
> is anything.
> Regards
> Paul
> On Mon, Jan 16, 2017 at 3:58 PM, <cdelect at juno.com> wrote:
>> I've been doing some work on testing some HP 5061A/B tubes
>> and came across something that's not making any sense!
>> The R11 and R12 values marked on the tubes for use with the
>> new style A11 are supposed to reflect a parallel value
>> that is 10X larger than the thermistor reading.
>> This to agree with the ratio of the bridge resistors in the
>> A11 module.
>> For instance a 3112A prefix tube shows values of 3.83K
>> and 42.2K. This gives a parallel value of 3.511K which when
>> divided by 10 gives 351.1 Ohm. The value marked on the tube
>> was 352 Ohm. That all makes sense!
>> Now I have three 3232A prefix tubes and they all do not
>> reflect this ratio.
>> For instance one has values of 51.1K and 5.11K which gives
>> 4.65K. This divided by ten gives 465 Ohms. However the
>> Thermistor value marked on the tube is 915 Ohms!
>> I tested all three tubes and they come up to the proper
>> temperature with the thermistor value marked on the tube.
>> Did HP make a change to the A11 bridge resistor ratio, and
>> if so where did they document it!
>> If not and you used the R11 and R12 values you would
>> seriously overheat the tube!
>> Cheers,
>> Corby
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