Hi They had cans with holes in them for the adjust process. There is no practical way to do the adjustment ahead of time. They turn hunt the parts first. Then a temperature test is done and they are adjusted again. The test / adjust process continues until they meet spec. The turn hunt gets things close, the test / adjust takes care of the (non trivial) contribution of temperature gradients and oscillator / buffer TC.
Bob On May 12, 2013, at 6:45 PM, Frederick Bray <[email protected]> wrote: > Interestingly, there is a hole in the foam to adjust the pot. There is no > corresponding hole in the can, only one for the piston capacitor adjustment. > It appears that the pot is part of the oven control circuit. Maybe Ovenaire > had a test fixture to make the adjustment before putting everything in the > can? > > I am about to the point where I will probably just reassemble it and drill a > hole for the pot. (That won't be hard to do after looking at the distance > between the two existing holes in the foam and figuring out where the hole in > the can should go.) > > I have looked at the board under a lighted magnifier and can't see any cold > solder joints or similar flaws. I suppose I could heat each one up with a > soldering iron to make sure. I have tested all the resistors while in > circuit and all values read less than or equal to the marked values. I > realize that it is still possible that one has increased but that due to > other circuit components the reading is still less than the value of the > resistor. Perhaps I should just shotgun the ones in the oven control portion > of the circuit? I have found no open diodes. I also have turned the pot 1/2 > turn in each direction and returned it to its original position in the hope > that this will have cleaned it. > > I will have to go back into the power supply anyway. There are a couple of > strange things, such as the previously mentioned fluctuations on the 12 volt > line. Then, there is the fact that the -7 volt supply is still a volt too > low. It came up after I replaced some electrolytic capacitors and some out > of value resistors but there's still more to do. This doesn't impact the > OCXO as it only uses 12 volts. > > Thanks again for all the suggestions. > > Fred > > > > > > On 5/12/2013 3:16 PM, Don Latham wrote: >> If there's a pot set that's inside the case, indeed inside the "foam" >> then there has to be a procedure for setting it before final assembly, >> no? >> can't believe an engineering setup that requires tiny tweaks with >> assembly and disassembly. . . >> Don >> >> > > _______________________________________________ > 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. _______________________________________________ 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.
