); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY [EMAIL PROTECTED] said the following on 10/10/2007 02:39 PM:
> BTW: I wonder how much effect thermistor and resistor-bridge aging as well > as opamp offset drift has on the long term aging of typical OCXO's since it > will shift the temperature setpoint of the crystal. > > I think this is an issue that's not receiving a lot of attention in the > literature.. More anecdotes. I have a bunch of old Sulzer 2.5 and 5 oscillators. As Tom will happily tell you, one of these guys that still works well can be one of the best pieces of quartz you'll ever find (and a great toilet flush detector!). But most of mine are a bit flaky, and the thermistors seem to be the main problem. Each unit has at least two -- one is inside the inner oven and is part of a bridge that drives the "TEMP" meter position; it's supposed to read 0 when the oven is at temperature. Another is part of the bridge that sets the oven temperature; there are hand-chosen components designed to work with the thermistor to drive the heater to the right temperature. I've seen units where one or both was so far off, you couldn't really tell what the oven was doing. In at least one case, there was an open that drove the oven full blast continuously. Someday I'd like to build a test fixture that would allow measuring the crystal turning point and setting the ovens back to optimal temperature... So, aging of these parts can certainly be an issue. John _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
