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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