I have two 5061As that are (for the moment at least) working. Both have replacement FTS tubes, and both have the retrofitted 10811A OCXO. One is a fairly late chassis, while the other is much older. One difference is that the long time constant switch on the older one is a slide switch in the bottom of the control panel, while on the newer one LTC is an additional position on the main function switch.
The newer unit runs in LTC mode quite reliably. Its frequency shift when switching between short and long time constant is not too great, and can easily be adjusted with the C field control. But the older unit is interesting. When I switch it into LTC mode, it appears to work just fine, and the continuous operation lamp remains lit. However, the frequency shifts upward by about 2x10e-11, and even pulling the C field control all the way to zer0 doesn't make a lot of difference. As I understand it, leakage in the big capacitor that is switched in line to enable the long (60 second) time constant causes the frequency shift. I guess I'm not surprised that perhaps the cap in the older unit is more leaky, resulting in a greater shift. But I am surprised that the offset could be large enough (a) that it couldn't be tuned out via C field, yet (b) wouldn't trigger an alarm and cause the green light to go out. Has anyone here experienced anything like this? Might something else be going on? 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.
