OXCO Problem



Hi All


I have had a friend around today with his OXCO that he has just built, (M0CDL) he wasn’t sure how to calibrate it so came to me since I have 3 setup and working, it was oscillating fine no problem and past the tests in the build instructions but the current drain was sitting at about 400 mA to the heaters which  are getting nicely warm, the current doesn’t drop after time and sits there  with out change. I checked the output from IC1 and it was 5v, the trimer heat control didn’t make any difference, in the end I removed one side of R4 and rechecked, now the current was more or less zero to the heaters, which I would expect. The output from IC1 was still 5v,

With R4 out of circuit these are the voltages on the pins, yes the output from R21 is adjustable and sits just over 2v and moves up/down with adjusting R21 by +/- 0.25 v (approx. maybe a bit more than this )

IC1 pin voltages

Pin       Voltage

1                     5V

2                     2.13v

3                     3.4v

4                     5v

5                     5v

6                     5v

7                     2.8v

How do these voltage compare to design voltages I wonder????


Other than that the module is working, its just controlling the heater that is the problem.

Hope someone can help.

73 Paul M0BMN

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