Hi I'd bet that something is keeping the oscillator from putting out enough RF. The circuit is simple enough that the issue is one of a very small number of parts. I'd bet on the FET…..
Bob On Mar 17, 2013, at 8:24 PM, [email protected] wrote: > I am afraid the PRS-10 lamp starting algorithm is a little involved. I > believe that once the lamp temperature is in the starting range, the > microprocessor ramps up the drain and possibly gate voltage of the heating > oscillator FET until the bulb strikes as evidenced by a DC signal at the > detector. > If the lamp overheats (as measured by thermistors imbedded in the back of > the lamp block), at some point the microprocessor will reduce the drain > voltage to a safe steady-state value. > > The starting constants for each individual PRS-10 are factory-set in the > unit's programmed software, and as far as I know, access to change these > settings has not been made available yet to end users. This makes it > difficult to swap lamps between units. > > I have a PRS-10 with a lamp that is just on the edge of starting properly. > Since I cannot change the factory-programmed values, I have tried adding > a shunt resistor to increase the lamp current to the point where it would > reliably start. But, unfortunately, other problems seem to be keeping the > unit from working properly. > > The only luck I have had in repairing a non-working PRS-10 with certainty, > was one in a Symmetricom 2500 Time Source that turned out to have a failed > Mini-Circuits VCO on the synthesizer board. Replacing the VCO module > restored proper operation. > > Perhaps someday the factory will provide end users with access to what are > now "factory-only" settings. > > Bruce, KG6OJI > _______________________________________________ > 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.
