Re: [time-nuts] Datum 4065A Cs Tube Response
Ed, If I have the math correct, and you are measuring the voltage to ground through a 10 MegOhm input impedance DMM, you have about 7.5 nA beam current which seems a bit low compared to what I remember of the HP 5061A. However, you still have a definable 'peak' with a 'peak to valley' voltage of about 60 mV or a 'useful signal current' of about 6 nA. If your unit's circuitry can properly amplify that and keep it a clean signal, it should work. However, I would recommend setting the OCXO precisely on frequency with a GPSDO before trying to close the loop and 'locking' the signal to the CS tube. It will dramatically lower the work load of getting everything adjusted properly, particularly in a setting of low beam current. Somehow, the value of 40 nA sticks in my mind from the 5061A. The 5061A manual says end of life of the HP CS tube is a peak beam current of 8 nA or less. However, I have units with less current and they still lock. The HP manual also says to measure the voltage at the output of the tube with a 100 MegOhm or higher input impedance DMM. If yours is less, that may artificially lower your values. EOL of the tube is a multifactor issue, including Signal to Noise ratio and the 'useful signal current' to 'background current' ratio. The 'background current' is what you see with no RF signal applied to the tube. Have you measured that? A ratio of 1 is EOL per the HP manual. If yours is about 4.5 nA, as suggested by the 'off peak' values shown, or less, you still have a useful signal and, hopefully, a useful tube. I'd recommend continuing with the repair. Good luck. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Ed Palmer Sent: Monday, May 05, 2014 12:46 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Datum 4065A Cs Tube Response I'm playing with my first Cs standard. It's a Datum 4065A which appears to have a dead STEL-1173 synthesizer. Before I put too much effort into replacing that, I thought I'd check the tube and see if it has any life left. I've attached a chart showing the response of the central peak. My methodology was similar to TVB's as shown here: http://www.leapsecond.com/pages/cspeak except that I measured the tube output directly with a digital voltmeter. The system is reporting wildly varying levels for the beam current so I didn't want to use any of it's circuitry. Does this look like a usable tube? Healthy or on it's last legs? What response levels are typical for a Datum 7504A tube? I see that these levels are somewhat lower than those shown on leapsecond for the 5061A tube, but that could just be the specifics of the measurement. Thanks, Ed ___ 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] Datum 4065A Cs Tube Response
I will agree with Joe. I have a CS tube thats darn near impossible to read the beam current and yet it still locks. That truly amazes me. I seem to recall other comments ages ago about that chip failing. There should be a way to emulate it these days with all of the DDS chips and such that are available. Good luck. Regards Paul. WB8TSL On Mon, May 5, 2014 at 8:20 AM, J. L. Trantham jlt...@att.net wrote: Ed, If I have the math correct, and you are measuring the voltage to ground through a 10 MegOhm input impedance DMM, you have about 7.5 nA beam current which seems a bit low compared to what I remember of the HP 5061A. However, you still have a definable 'peak' with a 'peak to valley' voltage of about 60 mV or a 'useful signal current' of about 6 nA. If your unit's circuitry can properly amplify that and keep it a clean signal, it should work. However, I would recommend setting the OCXO precisely on frequency with a GPSDO before trying to close the loop and 'locking' the signal to the CS tube. It will dramatically lower the work load of getting everything adjusted properly, particularly in a setting of low beam current. Somehow, the value of 40 nA sticks in my mind from the 5061A. The 5061A manual says end of life of the HP CS tube is a peak beam current of 8 nA or less. However, I have units with less current and they still lock. The HP manual also says to measure the voltage at the output of the tube with a 100 MegOhm or higher input impedance DMM. If yours is less, that may artificially lower your values. EOL of the tube is a multifactor issue, including Signal to Noise ratio and the 'useful signal current' to 'background current' ratio. The 'background current' is what you see with no RF signal applied to the tube. Have you measured that? A ratio of 1 is EOL per the HP manual. If yours is about 4.5 nA, as suggested by the 'off peak' values shown, or less, you still have a useful signal and, hopefully, a useful tube. I'd recommend continuing with the repair. Good luck. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Ed Palmer Sent: Monday, May 05, 2014 12:46 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Datum 4065A Cs Tube Response I'm playing with my first Cs standard. It's a Datum 4065A which appears to have a dead STEL-1173 synthesizer. Before I put too much effort into replacing that, I thought I'd check the tube and see if it has any life left. I've attached a chart showing the response of the central peak. My methodology was similar to TVB's as shown here: http://www.leapsecond.com/pages/cspeak except that I measured the tube output directly with a digital voltmeter. The system is reporting wildly varying levels for the beam current so I didn't want to use any of it's circuitry. Does this look like a usable tube? Healthy or on it's last legs? What response levels are typical for a Datum 7504A tube? I see that these levels are somewhat lower than those shown on leapsecond for the 5061A tube, but that could just be the specifics of the measurement. Thanks, Ed ___ 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] Datum 4065A Cs Tube Response
Hi Ed, On 05/05/2014 07:45 AM, Ed Palmer wrote: I'm playing with my first Cs standard. It's a Datum 4065A which appears to have a dead STEL-1173 synthesizer. Before I put too much effort into replacing that, I thought I'd check the tube and see if it has any life left. I've attached a chart showing the response of the central peak. Looks nice. I had the same issue with one of my cesiums, so I got lucky and got a STEL 1173 in 44 pin PLCC, replaced it and then it worked. What happens is that the output drivers for the STEL 1173 dies one after another and eventually you end up noise. My methodology was similar to TVB's as shown here: http://www.leapsecond.com/pages/cspeak except that I measured the tube output directly with a digital voltmeter. The system is reporting wildly varying levels for the beam current so I didn't want to use any of it's circuitry. I found the suitable test-point and multiplied with the network analyzers output signal as replacing the 12.6 MHz signal, and then the output of that into the network analyzer and that way got a nice way of checking the tube. Does this look like a usable tube? Healthy or on it's last legs? What response levels are typical for a Datum 7504A tube? I see that these levels are somewhat lower than those shown on leapsecond for the 5061A tube, but that could just be the specifics of the measurement. Well, looks worth trying replaing the STEL for. Good luck and hope it works out for you! Cheers, Magnus ___ 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] Datum 4065A Cs Tube Response
Hi Joe, I didn't realize that the info in the 5061A manual was somewhat 'generic'. Thanks for the pointer. On 5/5/2014 6:20 AM, J. L. Trantham wrote: Ed, If I have the math correct, and you are measuring the voltage to ground through a 10 MegOhm input impedance DMM, you have about 7.5 nA beam current which seems a bit low compared to what I remember of the HP 5061A. However, you still have a definable 'peak' with a 'peak to valley' voltage of about 60 mV or a 'useful signal current' of about 6 nA. If your unit's circuitry can properly amplify that and keep it a clean signal, it should work. However, I would recommend setting the OCXO precisely on frequency with a GPSDO before trying to close the loop and 'locking' the signal to the CS tube. It will dramatically lower the work load of getting everything adjusted properly, particularly in a setting of low beam current. Easier said than done. This oscillator has no manual frequency adjustment and if there's an electrical one, I haven't found it yet. But the oscillator's response seems very vague as though it's just kind of wandering around so I think there's something not right there. It's likely related to the bad synthesizer chip. Somehow, the value of 40 nA sticks in my mind from the 5061A. The 5061A manual says end of life of the HP CS tube is a peak beam current of 8 nA or less. However, I have units with less current and they still lock. The HP manual also says to measure the voltage at the output of the tube with a 100 MegOhm or higher input impedance DMM. If yours is less, that may artificially lower your values. I reconfigured my test setup to use a 100 Mohm meter and converted the results into nanoamps. The 10 Mohm meter was loading down the tube a bit. The new graph looks somewhat better. EOL of the tube is a multifactor issue, including Signal to Noise ratio and the 'useful signal current' to 'background current' ratio. The 'background current' is what you see with no RF signal applied to the tube. Have you measured that? A ratio of 1 is EOL per the HP manual. If yours is about 4.5 nA, as suggested by the 'off peak' values shown, or less, you still have a useful signal and, hopefully, a useful tube. The ratio of signal level to background level looks quite good. The background current is only 1.5 na for a ratio of 6:1. I checked that measurement twice because it looked suspiciously good. I'd recommend continuing with the repair. I will, but it could be world's slowest repair as I try to find one of those synthesizer chips. I've seen places that claim to have them, but only in the 48 pin DIP package rather than the 44 pin PLCC. I REALLY don't want to do that conversion! In any case, I have many other toys to amuse me! :) Thanks for all the tips! Ed Good luck. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Ed Palmer Sent: Monday, May 05, 2014 12:46 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Datum 4065A Cs Tube Response I'm playing with my first Cs standard. It's a Datum 4065A which appears to have a dead STEL-1173 synthesizer. Before I put too much effort into replacing that, I thought I'd check the tube and see if it has any life left. I've attached a chart showing the response of the central peak. My methodology was similar to TVB's as shown here: http://www.leapsecond.com/pages/cspeak except that I measured the tube output directly with a digital voltmeter. The system is reporting wildly varying levels for the beam current so I didn't want to use any of it's circuitry. Does this look like a usable tube? Healthy or on it's last legs? What response levels are typical for a Datum 7504A tube? I see that these levels are somewhat lower than those shown on leapsecond for the 5061A tube, but that could just be the specifics of the measurement. Thanks, Ed ___ 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] Datum 4065A Cs Tube Response
I know very little about today's DDS chips, but I think that emulating the STEL-1173 would be a challenge. It provides 48 bit frequency resolution. I counted 13 different frequencies that are used to monitor the signal to make sure that it's on frequency. Based on the manual, they were shifting it many times per second. I'm not surprised the chip died - they worked it to death! Ed On 5/5/2014 6:49 AM, paul swed wrote: I will agree with Joe. I have a CS tube thats darn near impossible to read the beam current and yet it still locks. That truly amazes me. I seem to recall other comments ages ago about that chip failing. There should be a way to emulate it these days with all of the DDS chips and such that are available. Good luck. Regards Paul. WB8TSL On Mon, May 5, 2014 at 8:20 AM, J. L. Trantham jlt...@att.net wrote: Ed, If I have the math correct, and you are measuring the voltage to ground through a 10 MegOhm input impedance DMM, you have about 7.5 nA beam current which seems a bit low compared to what I remember of the HP 5061A. However, you still have a definable 'peak' with a 'peak to valley' voltage of about 60 mV or a 'useful signal current' of about 6 nA. If your unit's circuitry can properly amplify that and keep it a clean signal, it should work. However, I would recommend setting the OCXO precisely on frequency with a GPSDO before trying to close the loop and 'locking' the signal to the CS tube. It will dramatically lower the work load of getting everything adjusted properly, particularly in a setting of low beam current. Somehow, the value of 40 nA sticks in my mind from the 5061A. The 5061A manual says end of life of the HP CS tube is a peak beam current of 8 nA or less. However, I have units with less current and they still lock. The HP manual also says to measure the voltage at the output of the tube with a 100 MegOhm or higher input impedance DMM. If yours is less, that may artificially lower your values. EOL of the tube is a multifactor issue, including Signal to Noise ratio and the 'useful signal current' to 'background current' ratio. The 'background current' is what you see with no RF signal applied to the tube. Have you measured that? A ratio of 1 is EOL per the HP manual. If yours is about 4.5 nA, as suggested by the 'off peak' values shown, or less, you still have a useful signal and, hopefully, a useful tube. I'd recommend continuing with the repair. Good luck. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Ed Palmer Sent: Monday, May 05, 2014 12:46 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Datum 4065A Cs Tube Response I'm playing with my first Cs standard. It's a Datum 4065A which appears to have a dead STEL-1173 synthesizer. Before I put too much effort into replacing that, I thought I'd check the tube and see if it has any life left. I've attached a chart showing the response of the central peak. My methodology was similar to TVB's as shown here: http://www.leapsecond.com/pages/cspeak except that I measured the tube output directly with a digital voltmeter. The system is reporting wildly varying levels for the beam current so I didn't want to use any of it's circuitry. Does this look like a usable tube? Healthy or on it's last legs? What response levels are typical for a Datum 7504A tube? I see that these levels are somewhat lower than those shown on leapsecond for the 5061A tube, but that could just be the specifics of the measurement. Thanks, Ed ___ 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] Datum 4065A Cs Tube Response
Hi Is this the right chip: http://www.oemstrade.com/search/STEL-1173%252FCL/ At $65 it is pricy but a bargain if it fixes your clock. Thomas Knox Date: Mon, 5 May 2014 15:14:16 -0600 From: ed_pal...@sasktel.net To: time-nuts@febo.com Subject: Re: [time-nuts] Datum 4065A Cs Tube Response I know very little about today's DDS chips, but I think that emulating the STEL-1173 would be a challenge. It provides 48 bit frequency resolution. I counted 13 different frequencies that are used to monitor the signal to make sure that it's on frequency. Based on the manual, they were shifting it many times per second. I'm not surprised the chip died - they worked it to death! Ed On 5/5/2014 6:49 AM, paul swed wrote: I will agree with Joe. I have a CS tube thats darn near impossible to read the beam current and yet it still locks. That truly amazes me. I seem to recall other comments ages ago about that chip failing. There should be a way to emulate it these days with all of the DDS chips and such that are available. Good luck. Regards Paul. WB8TSL On Mon, May 5, 2014 at 8:20 AM, J. L. Trantham jlt...@att.net wrote: Ed, If I have the math correct, and you are measuring the voltage to ground through a 10 MegOhm input impedance DMM, you have about 7.5 nA beam current which seems a bit low compared to what I remember of the HP 5061A. However, you still have a definable 'peak' with a 'peak to valley' voltage of about 60 mV or a 'useful signal current' of about 6 nA. If your unit's circuitry can properly amplify that and keep it a clean signal, it should work. However, I would recommend setting the OCXO precisely on frequency with a GPSDO before trying to close the loop and 'locking' the signal to the CS tube. It will dramatically lower the work load of getting everything adjusted properly, particularly in a setting of low beam current. Somehow, the value of 40 nA sticks in my mind from the 5061A. The 5061A manual says end of life of the HP CS tube is a peak beam current of 8 nA or less. However, I have units with less current and they still lock. The HP manual also says to measure the voltage at the output of the tube with a 100 MegOhm or higher input impedance DMM. If yours is less, that may artificially lower your values. EOL of the tube is a multifactor issue, including Signal to Noise ratio and the 'useful signal current' to 'background current' ratio. The 'background current' is what you see with no RF signal applied to the tube. Have you measured that? A ratio of 1 is EOL per the HP manual. If yours is about 4.5 nA, as suggested by the 'off peak' values shown, or less, you still have a useful signal and, hopefully, a useful tube. I'd recommend continuing with the repair. Good luck. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Ed Palmer Sent: Monday, May 05, 2014 12:46 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Datum 4065A Cs Tube Response I'm playing with my first Cs standard. It's a Datum 4065A which appears to have a dead STEL-1173 synthesizer. Before I put too much effort into replacing that, I thought I'd check the tube and see if it has any life left. I've attached a chart showing the response of the central peak. My methodology was similar to TVB's as shown here: http://www.leapsecond.com/pages/cspeak except that I measured the tube output directly with a digital voltmeter. The system is reporting wildly varying levels for the beam current so I didn't want to use any of it's circuitry. Does this look like a usable tube? Healthy or on it's last legs? What response levels are typical for a Datum 7504A tube? I see that these levels are somewhat lower than those shown on leapsecond for the 5061A tube, but that could just be the specifics of the measurement. Thanks, Ed ___ 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] Datum 4065A Cs Tube Response
Ed, On 05/05/2014 10:56 PM, Ed Palmer wrote: Hi Joe, I didn't realize that the info in the 5061A manual was somewhat 'generic'. Thanks for the pointer. On 5/5/2014 6:20 AM, J. L. Trantham wrote: Ed, If I have the math correct, and you are measuring the voltage to ground through a 10 MegOhm input impedance DMM, you have about 7.5 nA beam current which seems a bit low compared to what I remember of the HP 5061A. However, you still have a definable 'peak' with a 'peak to valley' voltage of about 60 mV or a 'useful signal current' of about 6 nA. If your unit's circuitry can properly amplify that and keep it a clean signal, it should work. However, I would recommend setting the OCXO precisely on frequency with a GPSDO before trying to close the loop and 'locking' the signal to the CS tube. It will dramatically lower the work load of getting everything adjusted properly, particularly in a setting of low beam current. Easier said than done. This oscillator has no manual frequency adjustment and if there's an electrical one, I haven't found it yet. But the oscillator's response seems very vague as though it's just kind of wandering around so I think there's something not right there. It's likely related to the bad synthesizer chip. The 4065 use the STEL DDS to jump around in an interesting patten to measure the Zeeman position of the main lobe and of the first side-lobes to steer the C-field in a separate control-loop. This means that the C-field is completely under CPU control, and no manual trimming. I think you can disable this and steer it manual over the serial interface, but I don't recall the details. The 6 side-lobes separate with heavy dependence on the C-field, so servo-loop on their position relative the main lobe works really well. With the C-field servo-controlled like this, the C-field shift of the main lobe, which is a much weaker dependence and also one of the major aspects in selecting Cesiums in the first place, a more accurate Si-realization becomes possible, as well as with much better repeat in realization as the arbitrary C-field shift can be almost completely canceled. As the Zeeman steering and centering is done, locking to Rabi feature is done in a similar sense, by measuring multiple points. In fact, this is where it spends most of it's time and the for some of the TDM slots jump around for the Zeeman measuring points every once in a while. All that is described in a patent, which then describes this being driven by the 1802 CPU, but that was later replaced by the 6800-series. Precision time with whopping 8-bitters. It gives the same warm and fuzzy feeling as rubidium and cesiums with 741s in PSUs and control-loops :) So, this core looks pretty brainless with not as much fun trimmers as the 5061A for instance, but it has quite better brains, it's just that the faded STEL 1173 drivers makes it blind. The STEL 1173 DDS functionality isn't very hard to copy good enough, but it is still some work do be done. I don't remember where the datasheet went for it. Somehow, the value of 40 nA sticks in my mind from the 5061A. The 5061A manual says end of life of the HP CS tube is a peak beam current of 8 nA or less. However, I have units with less current and they still lock. The HP manual also says to measure the voltage at the output of the tube with a 100 MegOhm or higher input impedance DMM. If yours is less, that may artificially lower your values. I reconfigured my test setup to use a 100 Mohm meter and converted the results into nanoamps. The 10 Mohm meter was loading down the tube a bit. The new graph looks somewhat better. Great. EOL of the tube is a multifactor issue, including Signal to Noise ratio and the 'useful signal current' to 'background current' ratio. The 'background current' is what you see with no RF signal applied to the tube. Have you measured that? A ratio of 1 is EOL per the HP manual. If yours is about 4.5 nA, as suggested by the 'off peak' values shown, or less, you still have a useful signal and, hopefully, a useful tube. The ratio of signal level to background level looks quite good. The background current is only 1.5 na for a ratio of 6:1. I checked that measurement twice because it looked suspiciously good. Great. I'd recommend continuing with the repair. I will, but it could be world's slowest repair as I try to find one of those synthesizer chips. I've seen places that claim to have them, but only in the 48 pin DIP package rather than the 44 pin PLCC. I REALLY don't want to do that conversion! In any case, I have many other toys to amuse me! :) While you wait, don't waste that tube. Thanks for all the tips! I wish I had a 44 pin PLCC variant of the STEL 1173 lying around to help you out. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow
Re: [time-nuts] Datum 4065A Cs Tube Response
Hi Tom, Yes, that's the right chip, but the 'L' at the end means it's the DIP package. The PLCC package has an 'M' instead of the 'L'. I also found a lot of sellers on a far east site who have the DIP package (probably used chips pulled from sockets), but none who have the PLCC package. The price is also a lot less than $65, but of course, you're taking a risk that you might be buying a dead chip. Ed On 5/5/2014 3:18 PM, Tom Knox wrote: Hi Is this the right chip: http://www.oemstrade.com/search/STEL-1173%252FCL/ At $65 it is pricy but a bargain if it fixes your clock. Thomas Knox Date: Mon, 5 May 2014 15:14:16 -0600 From: ed_pal...@sasktel.net To: time-nuts@febo.com Subject: Re: [time-nuts] Datum 4065A Cs Tube Response I know very little about today's DDS chips, but I think that emulating the STEL-1173 would be a challenge. It provides 48 bit frequency resolution. I counted 13 different frequencies that are used to monitor the signal to make sure that it's on frequency. Based on the manual, they were shifting it many times per second. I'm not surprised the chip died - they worked it to death! Ed On 5/5/2014 6:49 AM, paul swed wrote: I will agree with Joe. I have a CS tube thats darn near impossible to read the beam current and yet it still locks. That truly amazes me. I seem to recall other comments ages ago about that chip failing. There should be a way to emulate it these days with all of the DDS chips and such that are available. Good luck. Regards Paul. WB8TSL On Mon, May 5, 2014 at 8:20 AM, J. L. Trantham jlt...@att.net wrote: Ed, If I have the math correct, and you are measuring the voltage to ground through a 10 MegOhm input impedance DMM, you have about 7.5 nA beam current which seems a bit low compared to what I remember of the HP 5061A. However, you still have a definable 'peak' with a 'peak to valley' voltage of about 60 mV or a 'useful signal current' of about 6 nA. If your unit's circuitry can properly amplify that and keep it a clean signal, it should work. However, I would recommend setting the OCXO precisely on frequency with a GPSDO before trying to close the loop and 'locking' the signal to the CS tube. It will dramatically lower the work load of getting everything adjusted properly, particularly in a setting of low beam current. Somehow, the value of 40 nA sticks in my mind from the 5061A. The 5061A manual says end of life of the HP CS tube is a peak beam current of 8 nA or less. However, I have units with less current and they still lock. The HP manual also says to measure the voltage at the output of the tube with a 100 MegOhm or higher input impedance DMM. If yours is less, that may artificially lower your values. EOL of the tube is a multifactor issue, including Signal to Noise ratio and the 'useful signal current' to 'background current' ratio. The 'background current' is what you see with no RF signal applied to the tube. Have you measured that? A ratio of 1 is EOL per the HP manual. If yours is about 4.5 nA, as suggested by the 'off peak' values shown, or less, you still have a useful signal and, hopefully, a useful tube. I'd recommend continuing with the repair. Good luck. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Ed Palmer Sent: Monday, May 05, 2014 12:46 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Datum 4065A Cs Tube Response I'm playing with my first Cs standard. It's a Datum 4065A which appears to have a dead STEL-1173 synthesizer. Before I put too much effort into replacing that, I thought I'd check the tube and see if it has any life left. I've attached a chart showing the response of the central peak. My methodology was similar to TVB's as shown here: http://www.leapsecond.com/pages/cspeak except that I measured the tube output directly with a digital voltmeter. The system is reporting wildly varying levels for the beam current so I didn't want to use any of it's circuitry. Does this look like a usable tube? Healthy or on it's last legs? What response levels are typical for a Datum 7504A tube? I see that these levels are somewhat lower than those shown on leapsecond for the 5061A tube, but that could just be the specifics of the measurement. Thanks, Ed ___ 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] Datum 4065A Cs Tube Response
Hi Ed: Some links to the related patents are on my 4060 4065 web page: http://www.prc68.com/I/FTS4060.shtml#Pat Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html Magnus Danielson wrote: Ed, On 05/05/2014 10:56 PM, Ed Palmer wrote: Hi Joe, I didn't realize that the info in the 5061A manual was somewhat 'generic'. Thanks for the pointer. On 5/5/2014 6:20 AM, J. L. Trantham wrote: Ed, If I have the math correct, and you are measuring the voltage to ground through a 10 MegOhm input impedance DMM, you have about 7.5 nA beam current which seems a bit low compared to what I remember of the HP 5061A. However, you still have a definable 'peak' with a 'peak to valley' voltage of about 60 mV or a 'useful signal current' of about 6 nA. If your unit's circuitry can properly amplify that and keep it a clean signal, it should work. However, I would recommend setting the OCXO precisely on frequency with a GPSDO before trying to close the loop and 'locking' the signal to the CS tube. It will dramatically lower the work load of getting everything adjusted properly, particularly in a setting of low beam current. Easier said than done. This oscillator has no manual frequency adjustment and if there's an electrical one, I haven't found it yet. But the oscillator's response seems very vague as though it's just kind of wandering around so I think there's something not right there. It's likely related to the bad synthesizer chip. The 4065 use the STEL DDS to jump around in an interesting patten to measure the Zeeman position of the main lobe and of the first side-lobes to steer the C-field in a separate control-loop. This means that the C-field is completely under CPU control, and no manual trimming. I think you can disable this and steer it manual over the serial interface, but I don't recall the details. The 6 side-lobes separate with heavy dependence on the C-field, so servo-loop on their position relative the main lobe works really well. With the C-field servo-controlled like this, the C-field shift of the main lobe, which is a much weaker dependence and also one of the major aspects in selecting Cesiums in the first place, a more accurate Si-realization becomes possible, as well as with much better repeat in realization as the arbitrary C-field shift can be almost completely canceled. As the Zeeman steering and centering is done, locking to Rabi feature is done in a similar sense, by measuring multiple points. In fact, this is where it spends most of it's time and the for some of the TDM slots jump around for the Zeeman measuring points every once in a while. All that is described in a patent, which then describes this being driven by the 1802 CPU, but that was later replaced by the 6800-series. Precision time with whopping 8-bitters. It gives the same warm and fuzzy feeling as rubidium and cesiums with 741s in PSUs and control-loops :) So, this core looks pretty brainless with not as much fun trimmers as the 5061A for instance, but it has quite better brains, it's just that the faded STEL 1173 drivers makes it blind. The STEL 1173 DDS functionality isn't very hard to copy good enough, but it is still some work do be done. I don't remember where the datasheet went for it. Somehow, the value of 40 nA sticks in my mind from the 5061A. The 5061A manual says end of life of the HP CS tube is a peak beam current of 8 nA or less. However, I have units with less current and they still lock. The HP manual also says to measure the voltage at the output of the tube with a 100 MegOhm or higher input impedance DMM. If yours is less, that may artificially lower your values. I reconfigured my test setup to use a 100 Mohm meter and converted the results into nanoamps. The 10 Mohm meter was loading down the tube a bit. The new graph looks somewhat better. Great. EOL of the tube is a multifactor issue, including Signal to Noise ratio and the 'useful signal current' to 'background current' ratio. The 'background current' is what you see with no RF signal applied to the tube. Have you measured that? A ratio of 1 is EOL per the HP manual. If yours is about 4.5 nA, as suggested by the 'off peak' values shown, or less, you still have a useful signal and, hopefully, a useful tube. The ratio of signal level to background level looks quite good. The background current is only 1.5 na for a ratio of 6:1. I checked that measurement twice because it looked suspiciously good. Great. I'd recommend continuing with the repair. I will, but it could be world's slowest repair as I try to find one of those synthesizer chips. I've seen places that claim to have them, but only in the 48 pin DIP package rather than the 44 pin PLCC. I REALLY don't want to do that conversion! In any case, I have many other toys to amuse me! :) While you wait, don't waste that tube. Thanks for all the tips! I wish I had a 44 pin PLCC variant of the STEL 1173
Re: [time-nuts] Datum 4065A Cs Tube Response
Hi Magnus, On 5/5/2014 3:30 PM, Magnus Danielson wrote: Ed, On 05/05/2014 10:56 PM, Ed Palmer wrote: Hi Joe, I didn't realize that the info in the 5061A manual was somewhat 'generic'. Thanks for the pointer. On 5/5/2014 6:20 AM, J. L. Trantham wrote: Ed, If I have the math correct, and you are measuring the voltage to ground through a 10 MegOhm input impedance DMM, you have about 7.5 nA beam current which seems a bit low compared to what I remember of the HP 5061A. However, you still have a definable 'peak' with a 'peak to valley' voltage of about 60 mV or a 'useful signal current' of about 6 nA. If your unit's circuitry can properly amplify that and keep it a clean signal, it should work. However, I would recommend setting the OCXO precisely on frequency with a GPSDO before trying to close the loop and 'locking' the signal to the CS tube. It will dramatically lower the work load of getting everything adjusted properly, particularly in a setting of low beam current. Easier said than done. This oscillator has no manual frequency adjustment and if there's an electrical one, I haven't found it yet. But the oscillator's response seems very vague as though it's just kind of wandering around so I think there's something not right there. It's likely related to the bad synthesizer chip. The 4065 use the STEL DDS to jump around in an interesting patten to measure the Zeeman position of the main lobe and of the first side-lobes to steer the C-field in a separate control-loop. This means that the C-field is completely under CPU control, and no manual trimming. I think you can disable this and steer it manual over the serial interface, but I don't recall the details. The 6 side-lobes separate with heavy dependence on the C-field, so servo-loop on their position relative the main lobe works really well. With the C-field servo-controlled like this, the C-field shift of the main lobe, which is a much weaker dependence and also one of the major aspects in selecting Cesiums in the first place, a more accurate Si-realization becomes possible, as well as with much better repeat in realization as the arbitrary C-field shift can be almost completely canceled. I was talking about adjusting the EFC for the OCXO, not the C-field, although I agree with what you've said. I hope that there's some kind of adjustment to compensate for crystal aging, but maybe not. Obviously, this tuning loop is also under CPU control and it appears that the failed DDS chip results in no RF to the tube at the right frequency so no signal for the main tuning loop to use to discipline the OCXO. Hence, the OCXO kind of wanders around. Even replacing the DDS with a fixed synthesizer wasn't enough to coax the CPU to discipline the OCXO. As the Zeeman steering and centering is done, locking to Rabi feature is done in a similar sense, by measuring multiple points. In fact, this is where it spends most of it's time and the for some of the TDM slots jump around for the Zeeman measuring points every once in a while. All that is described in a patent, which then describes this being driven by the 1802 CPU, but that was later replaced by the 6800-series. Precision time with whopping 8-bitters. It gives the same warm and fuzzy feeling as rubidium and cesiums with 741s in PSUs and control-loops :) So, this core looks pretty brainless with not as much fun trimmers as the 5061A for instance, but it has quite better brains, it's just that the faded STEL 1173 drivers makes it blind. The STEL 1173 DDS functionality isn't very hard to copy good enough, but it is still some work do be done. I don't remember where the datasheet went for it. It wasn't hard to find the datasheet. I was surprised to find that Intel took over the part. I don't know how long they carried it, but the datasheet was from them. Somehow, the value of 40 nA sticks in my mind from the 5061A. The 5061A manual says end of life of the HP CS tube is a peak beam current of 8 nA or less. However, I have units with less current and they still lock. The HP manual also says to measure the voltage at the output of the tube with a 100 MegOhm or higher input impedance DMM. If yours is less, that may artificially lower your values. I reconfigured my test setup to use a 100 Mohm meter and converted the results into nanoamps. The 10 Mohm meter was loading down the tube a bit. The new graph looks somewhat better. Great. EOL of the tube is a multifactor issue, including Signal to Noise ratio and the 'useful signal current' to 'background current' ratio. The 'background current' is what you see with no RF signal applied to the tube. Have you measured that? A ratio of 1 is EOL per the HP manual. If yours is about 4.5 nA, as suggested by the 'off peak' values shown, or less, you still have a useful signal and, hopefully, a useful tube. The ratio of signal level to background level looks quite good. The
Re: [time-nuts] Datum 4065A Cs Tube Response
The original price of the STEL1173CL was $ 125 in quantity 10 so $ 65 is a bargain. I have no idea as to how it is used in the 4065A but if it is limited to 13 frequencies it may be worth wile to take a look at the AD 9913 it is capable to produce very precise frequencies exceeding its 32 bits, tvb did run tests on a board we build and I have extra boards available. Has a PIC on it that may help to emulate. Most likely will it not be the only STEL failure. Bert Kehren In a message dated 5/5/2014 5:15:01 P.M. Eastern Daylight Time, ed_pal...@sasktel.net writes: I know very little about today's DDS chips, but I think that emulating the STEL-1173 would be a challenge. It provides 48 bit frequency resolution. I counted 13 different frequencies that are used to monitor the signal to make sure that it's on frequency. Based on the manual, they were shifting it many times per second. I'm not surprised the chip died - they worked it to death! Ed On 5/5/2014 6:49 AM, paul swed wrote: I will agree with Joe. I have a CS tube thats darn near impossible to read the beam current and yet it still locks. That truly amazes me. I seem to recall other comments ages ago about that chip failing. There should be a way to emulate it these days with all of the DDS chips and such that are available. Good luck. Regards Paul. WB8TSL On Mon, May 5, 2014 at 8:20 AM, J. L. Trantham jlt...@att.net wrote: Ed, If I have the math correct, and you are measuring the voltage to ground through a 10 MegOhm input impedance DMM, you have about 7.5 nA beam current which seems a bit low compared to what I remember of the HP 5061A. However, you still have a definable 'peak' with a 'peak to valley' voltage of about 60 mV or a 'useful signal current' of about 6 nA. If your unit's circuitry can properly amplify that and keep it a clean signal, it should work. However, I would recommend setting the OCXO precisely on frequency with a GPSDO before trying to close the loop and 'locking' the signal to the CS tube. It will dramatically lower the work load of getting everything adjusted properly, particularly in a setting of low beam current. Somehow, the value of 40 nA sticks in my mind from the 5061A. The 5061A manual says end of life of the HP CS tube is a peak beam current of 8 nA or less. However, I have units with less current and they still lock. The HP manual also says to measure the voltage at the output of the tube with a 100 MegOhm or higher input impedance DMM. If yours is less, that may artificially lower your values. EOL of the tube is a multifactor issue, including Signal to Noise ratio and the 'useful signal current' to 'background current' ratio. The 'background current' is what you see with no RF signal applied to the tube. Have you measured that? A ratio of 1 is EOL per the HP manual. If yours is about 4.5 nA, as suggested by the 'off peak' values shown, or less, you still have a useful signal and, hopefully, a useful tube. I'd recommend continuing with the repair. Good luck. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Ed Palmer Sent: Monday, May 05, 2014 12:46 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Datum 4065A Cs Tube Response I'm playing with my first Cs standard. It's a Datum 4065A which appears to have a dead STEL-1173 synthesizer. Before I put too much effort into replacing that, I thought I'd check the tube and see if it has any life left. I've attached a chart showing the response of the central peak. My methodology was similar to TVB's as shown here: http://www.leapsecond.com/pages/cspeak except that I measured the tube output directly with a digital voltmeter. The system is reporting wildly varying levels for the beam current so I didn't want to use any of it's circuitry. Does this look like a usable tube? Healthy or on it's last legs? What response levels are typical for a Datum 7504A tube? I see that these levels are somewhat lower than those shown on leapsecond for the 5061A tube, but that could just be the specifics of the measurement. Thanks, Ed ___ 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] Datum 4065A Cs Tube Response
The datasheet can be easily found with google. The functionality is very simple, it could be emulated with a CPLD+small memory or with an small FPGA (maybe the newer CPLDs from Altera.. they are FPGAs inside... and I think they have block RAM). But if you can still buy it in another package it would be cheaper and easier to make an adapter and be done with it. Daniel Em 05/05/2014 18:40, Ed Palmer escreveu: Hi Tom, Yes, that's the right chip, but the 'L' at the end means it's the DIP package. The PLCC package has an 'M' instead of the 'L'. I also found a lot of sellers on a far east site who have the DIP package (probably used chips pulled from sockets), but none who have the PLCC package. The price is also a lot less than $65, but of course, you're taking a risk that you might be buying a dead chip. Ed On 5/5/2014 3:18 PM, Tom Knox wrote: Hi Is this the right chip: http://www.oemstrade.com/search/STEL-1173%252FCL/ At $65 it is pricy but a bargain if it fixes your clock. Thomas Knox Date: Mon, 5 May 2014 15:14:16 -0600 From: ed_pal...@sasktel.net To: time-nuts@febo.com Subject: Re: [time-nuts] Datum 4065A Cs Tube Response I know very little about today's DDS chips, but I think that emulating the STEL-1173 would be a challenge. It provides 48 bit frequency resolution. I counted 13 different frequencies that are used to monitor the signal to make sure that it's on frequency. Based on the manual, they were shifting it many times per second. I'm not surprised the chip died - they worked it to death! Ed On 5/5/2014 6:49 AM, paul swed wrote: I will agree with Joe. I have a CS tube thats darn near impossible to read the beam current and yet it still locks. That truly amazes me. I seem to recall other comments ages ago about that chip failing. There should be a way to emulate it these days with all of the DDS chips and such that are available. Good luck. Regards Paul. WB8TSL On Mon, May 5, 2014 at 8:20 AM, J. L. Trantham jlt...@att.net wrote: Ed, If I have the math correct, and you are measuring the voltage to ground through a 10 MegOhm input impedance DMM, you have about 7.5 nA beam current which seems a bit low compared to what I remember of the HP 5061A. However, you still have a definable 'peak' with a 'peak to valley' voltage of about 60 mV or a 'useful signal current' of about 6 nA. If your unit's circuitry can properly amplify that and keep it a clean signal, it should work. However, I would recommend setting the OCXO precisely on frequency with a GPSDO before trying to close the loop and 'locking' the signal to the CS tube. It will dramatically lower the work load of getting everything adjusted properly, particularly in a setting of low beam current. Somehow, the value of 40 nA sticks in my mind from the 5061A. The 5061A manual says end of life of the HP CS tube is a peak beam current of 8 nA or less. However, I have units with less current and they still lock. The HP manual also says to measure the voltage at the output of the tube with a 100 MegOhm or higher input impedance DMM. If yours is less, that may artificially lower your values. EOL of the tube is a multifactor issue, including Signal to Noise ratio and the 'useful signal current' to 'background current' ratio. The 'background current' is what you see with no RF signal applied to the tube. Have you measured that? A ratio of 1 is EOL per the HP manual. If yours is about 4.5 nA, as suggested by the 'off peak' values shown, or less, you still have a useful signal and, hopefully, a useful tube. I'd recommend continuing with the repair. Good luck. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Ed Palmer Sent: Monday, May 05, 2014 12:46 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Datum 4065A Cs Tube Response I'm playing with my first Cs standard. It's a Datum 4065A which appears to have a dead STEL-1173 synthesizer. Before I put too much effort into replacing that, I thought I'd check the tube and see if it has any life left. I've attached a chart showing the response of the central peak. My methodology was similar to TVB's as shown here: http://www.leapsecond.com/pages/cspeak except that I measured the tube output directly with a digital voltmeter. The system is reporting wildly varying levels for the beam current so I didn't want to use any of it's circuitry. Does this look like a usable tube? Healthy or on it's last legs? What response levels are typical for a Datum 7504A tube? I see that these levels are somewhat lower than those shown on leapsecond for the 5061A tube, but that could just be the specifics of the measurement. Thanks, Ed ___ 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
[time-nuts] Datum 4065A Cs Tube Response
I'm playing with my first Cs standard. It's a Datum 4065A which appears to have a dead STEL-1173 synthesizer. Before I put too much effort into replacing that, I thought I'd check the tube and see if it has any life left. I've attached a chart showing the response of the central peak. My methodology was similar to TVB's as shown here: http://www.leapsecond.com/pages/cspeak except that I measured the tube output directly with a digital voltmeter. The system is reporting wildly varying levels for the beam current so I didn't want to use any of it's circuitry. Does this look like a usable tube? Healthy or on it's last legs? What response levels are typical for a Datum 7504A tube? I see that these levels are somewhat lower than those shown on leapsecond for the 5061A tube, but that could just be the specifics of the measurement. Thanks, Ed ___ 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.
