[time-nuts] AN/URQ-10A

[paul swed]

I can say inners always take a lot longer
The battery pack being out may be effecting some critical voltage
Just a guess
Paul
WB8TSL


On Fri, Apr 26, 2013 at 5:07 PM, <engineering at mt.net> wrote:

> To all,
>
> I acquired a AN/URQ-10A frequency standard which appears to have received
> little or no service since its birth.  There are no signs of ever being
> mounted in its mating rack and the unit has virtually no scratches or wear
> marks on it.
>
> Last night I finally managed to plug it in to see how it behaved.
>  Obviously the D NiCads in the battery module were flat and need
> replacement so I left the battery module out of the unit.  As expected, the
> unit powered up with all normal indications on the meter except for the
> outer and inner ovens.  After about three hours the indication for the
> outer oven became normal but after four hours I still did not have any
> indication on the inner oven reading.  By that time my pillow was calling
> me so I unplugged the unit to wait for further investigation fearing that
> if the heater was stuck full on, internal heat damage may result (if it
> hasn't already).
>
> But I did witness one observation that the inner oven meter indication
> briefly tweaked as the power supply was shutting down telling me that the
> heater element itself has continuity.  This told me that the heater was
> probably hot and when the power went down, the control circuitry shut the
> heater drive transistor off (don't know if anyone has observed the design
> of the metering circuit in this thing but the meter is connected between
> the heater and the collector of the drive transistor.  When cold, the
> transistor is fully conducting thereby pulling this point to ground.  As
> the temperature reaches equilibrium, this point then become positive as the
> drive transistor starts to reduce conduction.  The meter then sees a
> voltage at this point and indicates proper heater operation).
>
> Question #1: Does anyone have an idea as to how long one should wait to
> see an indication of inner oven operation?  Given the time it took for the
> outer oven to come up, do I need more patience?
>
> Comment/question #2: I did download the schematics for the URQ-10 (not A
> version) from the febo website but after a little disassembly and from
> obvious indication of additional controls on the non-A URQ-10 schematics,
> this A version is a horse of a different color.  A diligent search of the
> Internet has produced no results of information on the A version except for
> one original NAVSHIPS OP/SVC manual for it that went on eBay a little while
> ago (drats!).
>
> Comment/question #3: Not investing any additional time last night (sleep
> required), I simply tapped on the FE-10 oscillator module enclosure and
> found it to be as solid as a rock.  I don't have time to do more peeking at
> present but assume that this is due to (what I believe) is a Dewar
> enclosure that is contained inside. Correct?  If the inner oven has
> cratered, is the internal oven control circuitry contained in this
> enclosure accessible by any means or is it sealed forever?
>
> This unit may be old but it is certainly near collector status with
> regards to its physical condition.
>
> Any help, especially schematics, would be appreciated.
>
> Regards,
>
> Greg Muir
>
>
>
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