Not familiar with the oven, but that's a classic case of a PID controller with too much gain. If analog control parts are used, look for defective parts that determine amplifier gain. If it's done with a microprocessor, look for a physical cause like too much voltage to the oven or shorted turns that reduce the oven resistance.
It could also be a faulty mounting of the temperature sensor that introduces too much time delay in the loop. Bill Hawkins -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Yuri Ostry Sent: Saturday, June 08, 2013 10:30 AM To: [email protected] Subject: [time-nuts] "Chinese" MV89A OCXO oven oscillation Hello, Does anyone have any experience in fixing MV89A's that have oven oscillation after warm-up (current consumption fluctuate with a 0.8-0.9 sec period from almost zero to approx 0.7A)? While cold, OCXO drawing about 0.96A and there is no fluctuations. During warm-up current drops, and somewhere around 0.55A it started to oscillate. Amplitude of oscillation is rising slowly, and in a minute or two reaches maximum. Purchased three OCXO from ggg*fitting few months ago. As always, good working condition was promised. Two of three had really good external appearance, third was dropped, one of corners was bent. Just got time to test - all three were defective (broken output bypass cap). One in addition have lots of spurs in output spectrum, and another have oscillating oven. -- Sincerely, Yuri mailto:[email protected] _______________________________________________ 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.
