Re: [time-nuts] Repair of PRS10 Lamp Assembly
Thanks for all your comments so far. I did sniffing with a cable loop located in the lamp cell (thank you Bob for this advice), and surprise (!) RF power does not degrade with time but does stay rock solid after ignition. So, sorry Bob, you did not win the bet this time. Next step should be to check, what is going on with heating. Not so easy since all the many diagnostics are within range. As a provisory measure I decided to cheat the lamp heat regulator somehow by paralleling a 39 KOhm resistor to R226 an thereby shifting the operating point of the thermistors in lamp assembly. PPR10, when started properly, now seems to work as expected. One comment to the lamp starting algorithm: oscillator FET drain and gate voltage are controlled via factory set values but not on an individual basis. All lamps are started with FET voltage set to maximum available via SD2=255 and after inginition to some reduced value also via SD2=55. So there is no need to change set values for different lamp assemblies. Goetz Am 18.03.2013 01:34, : 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, brucekar...@aol.com 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 -- 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. ___ 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.
Re: [time-nuts] Repair of PRS10 Lamp Assembly
Hi Unless the PRS10 is very unusual in it's operation there are two things to check early in the debug process: 1) Is the oven heating up to roughly the right temperature? 2) The lamp is lit by RF energy. If the oscillator / amplifier supplying the RF isn't putting out as much as it should (or what it should) the lamp will not stay lit. I'd bet on number 2 in your case. There are many other possibilities, but I'd check those two first. Bob On Mar 17, 2013, at 5:22 AM, Dr. Götz Romahn go...@g-romahn.de wrote: dear all, beeing a silent reader of this list for a while, I now ask my first question. I have obtained a PRS10 that was declared faulty and it is. The problem I located in lamp assy. Lamp ignites only after warming up and pushing by a voltage kick from abt. 24V to abt 28V on the -24_heat line for some seconds. PRS10 gets locked there after and rbmon shows a seemingly healthy unit (see attachment). But... within some 15 to 45 minutes later light from lamp degrades as seen through LAMP VIEW hole in top board as well as AD9 Photocell I/V going down from 1.68 after ignition to 0.158 and lock is lost of course. Since all heating and voltage diagnostics do stay within accepted limits I suspect some problem within lamp enclosure (see attachment). Your help for further diagnosis and any hints for obtaining spare parts would be appreciated very much. Cheers Goetz PRS10 after ignition.jpglamp-assy.jpg___ 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.
Re: [time-nuts] Repair of PRS10 Lamp Assembly
My 2 cents and it is that. The FRS use a higher voltage say 24 V and on ignition that drops back. I have also seen on time-nuts older systems that actually use an ignition voltage to trigger the lamp. But I agree that it sounds like the RF might be low. The bulb does need to be heated to get to the right color temperature also. On Sun, Mar 17, 2013 at 9:03 AM, Bob Camp li...@rtty.us wrote: Hi Unless the PRS10 is very unusual in it's operation there are two things to check early in the debug process: 1) Is the oven heating up to roughly the right temperature? 2) The lamp is lit by RF energy. If the oscillator / amplifier supplying the RF isn't putting out as much as it should (or what it should) the lamp will not stay lit. I'd bet on number 2 in your case. There are many other possibilities, but I'd check those two first. Bob On Mar 17, 2013, at 5:22 AM, Dr. Götz Romahn go...@g-romahn.de wrote: dear all, beeing a silent reader of this list for a while, I now ask my first question. I have obtained a PRS10 that was declared faulty and it is. The problem I located in lamp assy. Lamp ignites only after warming up and pushing by a voltage kick from abt. 24V to abt 28V on the -24_heat line for some seconds. PRS10 gets locked there after and rbmon shows a seemingly healthy unit (see attachment). But... within some 15 to 45 minutes later light from lamp degrades as seen through LAMP VIEW hole in top board as well as AD9 Photocell I/V going down from 1.68 after ignition to 0.158 and lock is lost of course. Since all heating and voltage diagnostics do stay within accepted limits I suspect some problem within lamp enclosure (see attachment). Your help for further diagnosis and any hints for obtaining spare parts would be appreciated very much. Cheers Goetz PRS10 after ignition.jpglamp-assy.jpg___ 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. ___ 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.
Re: [time-nuts] Repair of PRS10 Lamp Assembly
thank you for fast responses. As I wrote in my posting, heating seems to be ok as reported by the PRS10 diagnostic tools. I agree with Bob and Paul: RF seems to degrade with warming up, but how can I test this. Remember, lamp and oscillator of PRS10 are not!!! accessible during operation and what part of hte oscillator could be the culprit ( and why do you think it is) ? Goetz Am 17.03.2013 20:59, : My 2 cents and it is that. The FRS use a higher voltage say 24 V and on ignition that drops back. I have also seen on time-nuts older systems that actually use an ignition voltage to trigger the lamp. But I agree that it sounds like the RF might be low. The bulb does need to be heated to get to the right color temperature also. On Sun, Mar 17, 2013 at 9:03 AM, Bob Camp li...@rtty.us wrote: Hi Unless the PRS10 is very unusual in it's operation there are two things to check early in the debug process: 1) Is the oven heating up to roughly the right temperature? 2) The lamp is lit by RF energy. If the oscillator / amplifier supplying the RF isn't putting out as much as it should (or what it should) the lamp will not stay lit. I'd bet on number 2 in your case. There are many other possibilities, but I'd check those two first. Bob On Mar 17, 2013, at 5:22 AM, Dr. Götz Romahn go...@g-romahn.de wrote: dear all, beeing a silent reader of this list for a while, I now ask my first question. I have obtained a PRS10 that was declared faulty and it is. The problem I located in lamp assy. Lamp ignites only after warming up and pushing by a voltage kick from abt. 24V to abt 28V on the -24_heat line for some seconds. PRS10 gets locked there after and rbmon shows a seemingly healthy unit (see attachment). But... within some 15 to 45 minutes later light from lamp degrades as seen through LAMP VIEW hole in top board as well as AD9 Photocell I/V going down from 1.68 after ignition to 0.158 and lock is lost of course. Since all heating and voltage diagnostics do stay within accepted limits I suspect some problem within lamp enclosure (see attachment). Your help for further diagnosis and any hints for obtaining spare parts would be appreciated very much. Cheers Goetz PRS10 after ignition.jpglamp-assy.jpg___ 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. ___ 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.
Re: [time-nuts] Repair of PRS10 Lamp Assembly
Hi I'd fashion a simple loop on the end of a coax and use it to sniff the RF in the vicinity of the cell. You are after a relative measure, so simply knowing if it drops with time or not should tell you which way to go in the troubleshooting. Normally a spectrum analyzer is a good device to monitor the loop with, there are other ways to do it as well. Bob On Mar 17, 2013, at 4:50 PM, Dr. Götz Romahn go...@g-romahn.de wrote: thank you for fast responses. As I wrote in my posting, heating seems to be ok as reported by the PRS10 diagnostic tools. I agree with Bob and Paul: RF seems to degrade with warming up, but how can I test this. Remember, lamp and oscillator of PRS10 are not!!! accessible during operation and what part of hte oscillator could be the culprit ( and why do you think it is) ? Goetz Am 17.03.2013 20:59, : My 2 cents and it is that. The FRS use a higher voltage say 24 V and on ignition that drops back. I have also seen on time-nuts older systems that actually use an ignition voltage to trigger the lamp. But I agree that it sounds like the RF might be low. The bulb does need to be heated to get to the right color temperature also. On Sun, Mar 17, 2013 at 9:03 AM, Bob Camp li...@rtty.us wrote: Hi Unless the PRS10 is very unusual in it's operation there are two things to check early in the debug process: 1) Is the oven heating up to roughly the right temperature? 2) The lamp is lit by RF energy. If the oscillator / amplifier supplying the RF isn't putting out as much as it should (or what it should) the lamp will not stay lit. I'd bet on number 2 in your case. There are many other possibilities, but I'd check those two first. Bob On Mar 17, 2013, at 5:22 AM, Dr. Götz Romahn go...@g-romahn.de wrote: dear all, beeing a silent reader of this list for a while, I now ask my first question. I have obtained a PRS10 that was declared faulty and it is. The problem I located in lamp assy. Lamp ignites only after warming up and pushing by a voltage kick from abt. 24V to abt 28V on the -24_heat line for some seconds. PRS10 gets locked there after and rbmon shows a seemingly healthy unit (see attachment). But... within some 15 to 45 minutes later light from lamp degrades as seen through LAMP VIEW hole in top board as well as AD9 Photocell I/V going down from 1.68 after ignition to 0.158 and lock is lost of course. Since all heating and voltage diagnostics do stay within accepted limits I suspect some problem within lamp enclosure (see attachment). Your help for further diagnosis and any hints for obtaining spare parts would be appreciated very much. Cheers Goetz PRS10 after ignition.jpglamp-assy.jpg___ 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. ___ 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. ___ 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.
Re: [time-nuts] Repair of PRS10 Lamp Assembly
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 -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Repair of PRS10 Lamp Assembly
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, brucekar...@aol.com 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 -- 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.
Re: [time-nuts] Repair of PRS10 Lamp Assembly
On Sun, Mar 17, 2013 at 08:24:37PM -0400, brucekar...@aol.com 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 -- 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.
