Bob, I still have a problem with the various theories. Again, how is it measured? If you have a production line, you don't want a "tweak" that requires hours or days to determine.
As far as setting the crystal set point (presumably the inner over set point), that makes even less sense. Consider that they clearly knew the turn over point of the crystal BEFORE it was packaged. They wrote it on the sticker inside. So, they would have no need to adjust the inner oven. That could easily have been done on the bench during assembly. It could also be done via a selection from a standardized set of components. That temperature is "sort of" critical. The curve is very flat, to it could be a little off. Since they knew the crystal turn over point in advance, there wouldn't be any need to "hunt" for it by an elaborate procedure after assembly. However, the temperature of the outer oven is much less critical and I would suspect is simply set by the choice of components. And, if it needed tweaking then it could also have been done on the bench. Since they would know the thermal transfer characteristics, I suppose that they could measure the outer case's temperature to deduce the correct temperature of the outer oven. But, again, that doesn't make sense from a production standpoint. It would simply take too long. Perhaps, they would be willing to eat the time needed for that type of adjustment, but it doesn't seem likely. All they would need to do would be to add some monitoring circuits that they could access. I've seen that type of thing a lot. It would be cheaper to add a few circuits for a quick adjustment than it would be to spend the time on the adjustment. People's time is worth a lot more than a few components. On the other hand, tweaking the output voltage is something that is quickly measured as part of testing. Put it in a jig, make a quick check for functionality, tweak the output voltage and you are done. Or, perhaps it adjusts the duty cycle, the bias point or some other characteristic of the output signal. Perhaps it adjusts the reference voltage. I think I showed that it doesn't make a large change in the frequency. But, it doesn't make sense for it to make a small change (although I would be unable to measure a small change). I think that there are a lot of unexplored possibilities, but I definitely am not convinced that it sets either the inner or outer oven temperature. There are simply better ways to do that in production. I really, really want to know, though! I am going to try to repair mine one more time and see what I can measure. I didn't try very hard the first time, but I think its worth doing. If I can get it repaired again (I have to fix some traces, especially for the ground pin) it will probably take a couple of days. I have the parts to fix my fan circuit in my oscilloscope and I will do that first. And possibly tweak the power supply capacitors to reduce noise. Mike > If this is a double oven, there are two oven circuits and two oven > controllers. > Both would have a set point and both would be adjusted somehow. The pot > may be the adjustment on the outer oven. Get things all set up and packaged, > then adjust the outer oven to make things do what the should do. _______________________________________________ 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.
