[time-nuts] cesium clocks..
wje at quackers.net
Fri Jun 27 20:14:54 EDT 2008
In this case, the temp thermistor bridge is outside the oven cavity
itself. The cable only passes power and the already-processed bridge
delta to the heater power amp. So, there's no particular benefit from
having the cable stuck to the heater wrap. (at least, I think so; my
basic failure was because the cable fried and shorted power to ground)
They said 'Windows or better'
so I used Linux.
Bruce Griffiths wrote:
Yes, but my comment is rather specific... my oscillator failed because
the heater pass transistor shorted.
This sent the oven heater into full-on. The overtemp sensor is far
removed from the heater. There's a ribbon cable between the driver board
and the temp bridge sensor board that runs directly over the heater, not
outside the oven insulation. Net result, transistor shorts, cable fries
before overtemp fuse opens. There's no reason the cable should be inside
the oven insulation.
My rebuild fix - (after removing all the carbonized foam insulation)
refoam the oven, replacing the cable and transistor, and moving it
outside the foam!
While I respect in general the brilliance of HP engineers, my classmate
was one, this isn't one of the more intelligent decisions.
The usual reason for running temperature sensor leads over the oven
inside the insulation is to thermally shunt them to the oven reducing
heat transfer to the temperature sensor via the wiring.
Your modification may reduce the oven temperature stability significantly.
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