On Sun, Mar 17, 2013 at 08:24:37PM -0400, [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. Assuming that this is the correct image for an PRS-10 (http://goo.gl/Q4ztp), the CPU used looks like an MC68HC711E20CFN3 (http://goo.gl/Zhxzv) which would mean that it should be simple to reverse engineer the program and data stored there .... > 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. If there is really an interest in this, just send me one or maybe two units and I'll give it a try, no promises though, but I've done a lot of work with motorola CPUs in the past ... best, Herbert > 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.
