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

cdelect at juno.com cdelect at juno.com
Mon Jan 16 15:58:09 EST 2017

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!



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