Other idea than leaving the 6K8 resistor?
On Thu, Apr 3, 2014 at 5:08 PM, Javier Herrero <jherr...@hvsistemas.es>wrote: > Hello all, > > I've a 1111C OCXO (inside a Symmetricom 5045A that is inside an > Oscilloquartz OSA 5585) that refuses to start. It seems that one voltage > regulator is not operating, with only 2V at its output while it should have > (I think...) around 12V. I've partially analyzed the circuit, and it is > nothing from other world: a 6.9V reference diode, driving an operational > amplifier, driving a NPN transistor. But the 6.9V reference diode is biased > from the regulator output, so... if the regulator does not provide output, > the zener is not biased, and then... the regulator does not provide output. > So it must be some kind of start-up circuit, that makes the transistor to > conduct a bit, or to bias the diode, when power is applied. > > I've been looking around, but not found it yet. I have make a quick test > by placing a 6k8 resistor between the collector and the base of the > transistor to make it conduct, and then the regulator starts, provides > adequate output (12.5V), and also the 5MHz output appears. > > Any idea is welcome :) > > Best regards, > > Javier > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.