Re: [time-nuts] My NTGS50AA failed
Hi I have a Bolt that has a similar stuck EFC. In my case it’s not the OCXO either. There is some sort of failure on the inputs to the summing op amp that drives the output to the high end of the DAC’s range. Bob On Nov 13, 2014, at 9:06 PM, EB4APL eb4...@cembreros.jazztel.es wrote: Hello Nigel, Finally I got enough courage and removed the OCXO, you know what kind of task it is.. Fortunately I didn't spoiled the PCB so I'll install 2 smb connectors in the provided places, I don't want to return there if I need to change the oscillator. Well, the oscillator is ok, this is in some way bad news because the oscillator is easily replaceable, and the EFC voltage remains stuck on 5.02 V. Now I'll test the quad op-amp and the related parts. If they are ok the problem is in the Xilinx chip, something that cannot be replaced unless I get parts donor, even that way is very problematic since it is a 80 pin chip. I'll continue posting my findings. Best regards, Ignacio El 13/11/2014 a las 12:03, GandalfG8--- via time-nuts escribió: Hi Ignacio I'm sure removing the oscillator would make your faultfinding much more straightforward. When I removed mine I started out quite convinced I wouldn't be able to do it, even with the solder mostly removed from around the pins they were obviously quite a tight fit and all I had available at that time was a plunger type solder sucker and desoldering braid, as the bits on my old Pace desoldering kit were well past their best. The answer basically was lots of braid, lots of patience, and resisting like crazy any temptation to pull against a hole that wasn't fully released, but I certainly wouldn't want to do it that way again in a hurry. The desoldering gun I use now would make it easier but the holes are really a bit small for those oscillator pins. The good news though is that the connectors are there as a back up and fitting them definitely makes it more versatile. I had considered repeating the performance on another NTGS50AA and/or NTBW50AA, I really think I should but so far haven't found the courage:-) I think previous checks for 1PPS outputs might have been limited to the external connectors but it would make sense if it was available somewhere on the PCB, I'll try to get one powered up later and check your findings, if I can find a bit of space that us amongst the usual chaos! Regards Nigel GM8PZR In a message dated 13/11/2014 01:11:30 GMT Standard Time, eb4...@cembreros.jazztel.es writes: Hi Nigel, Thank you for the suggestions, I was trying to avoid the OCXO removal but I think that now it must be done. I was also playing with the idea of populating the connectors so an OCXO exchange could be easily made, this makes possible to try various oscillators. Meanwhile I has been probing and measuring a lot of points and by chance I found a very interesting thing: Probing TP33 (which is close to the Trimble chip (U2) and directly connected to pin 76) there is a 1PPS, 10 us wide signal. I've checked it and appears to be synchronous with the 1/2 PPS output so maybe it can be routed to an output, probably I'll replace the 1/2 PPS with it, using the existing drive circuit and connector since it is very straightforward. My only concern is if this signal only is there during the anomalous condition that I have now, I have to retest it after fixing it. I had asked several times if anybody had located a 1PPS signal on these units, but the responses were negative and I had not probed systematically the board before. Also I'm taking notes of the signals found and I'll try to make a partial schematic at least with the EFC circuitry. When I fix it I'll clean the notes and figures and I'll upload it to some place. Best regards, Ignacio El 12/11/2014 a las 11:47, GandalfG8--- via time-nuts escribió: Hi Ignacio I have removed a faulty oscillator from one of these, not one of my more relaxed moments and quite amazed when the board emerged totally undamaged, but proof at least that it can be done:-) With the oscillator removed there's access to two sets of connector pads that will either accept SMA or SMB connectors and after conducting tests on the original oscillator via flying leads just soldered to the board I decided not to fit a replacement to the board after all but to fit a couple of SMB connectors to make the setup more versatile, and to avoid the possibility of having to remove another oscillator in the future:-) Another advantage of these pads is that if the board does get damaged removing the oscillator they can still be used as an alternative. The connectors take the 10MHz from the oscillator into the board and the EFC control voltage out from the board to the oscillator, now there's a surprise:-), and oscillator power can be completely external if required. From this
Re: [time-nuts] My NTGS50AA failed
Hi, In my case, if the problem is the op-amp or some passive around, it can be easily replaced. If not the only solution is to find a parts unit to transplant the programmed Xilinx chip. Now I'm quite busy trying to get the schematic of the op-amp zone. Regards, Ignacio El 14/11/2014 a las 13:32, Bob Camp escribió: Hi I have a Bolt that has a similar stuck EFC. In my case it’s not the OCXO either. There is some sort of failure on the inputs to the summing op amp that drives the output to the high end of the DAC’s range. Bob On Nov 13, 2014, at 9:06 PM, EB4APL eb4...@cembreros.jazztel.es wrote: Hello Nigel, Finally I got enough courage and removed the OCXO, you know what kind of task it is.. Fortunately I didn't spoiled the PCB so I'll install 2 smb connectors in the provided places, I don't want to return there if I need to change the oscillator. Well, the oscillator is ok, this is in some way bad news because the oscillator is easily replaceable, and the EFC voltage remains stuck on 5.02 V. Now I'll test the quad op-amp and the related parts. If they are ok the problem is in the Xilinx chip, something that cannot be replaced unless I get parts donor, even that way is very problematic since it is a 80 pin chip. I'll continue posting my findings. Best regards, Ignacio El 13/11/2014 a las 12:03, GandalfG8--- via time-nuts escribió: Hi Ignacio I'm sure removing the oscillator would make your faultfinding much more straightforward. When I removed mine I started out quite convinced I wouldn't be able to do it, even with the solder mostly removed from around the pins they were obviously quite a tight fit and all I had available at that time was a plunger type solder sucker and desoldering braid, as the bits on my old Pace desoldering kit were well past their best. The answer basically was lots of braid, lots of patience, and resisting like crazy any temptation to pull against a hole that wasn't fully released, but I certainly wouldn't want to do it that way again in a hurry. The desoldering gun I use now would make it easier but the holes are really a bit small for those oscillator pins. The good news though is that the connectors are there as a back up and fitting them definitely makes it more versatile. I had considered repeating the performance on another NTGS50AA and/or NTBW50AA, I really think I should but so far haven't found the courage:-) I think previous checks for 1PPS outputs might have been limited to the external connectors but it would make sense if it was available somewhere on the PCB, I'll try to get one powered up later and check your findings, if I can find a bit of space that us amongst the usual chaos! Regards Nigel GM8PZR In a message dated 13/11/2014 01:11:30 GMT Standard Time, eb4...@cembreros.jazztel.es writes: Hi Nigel, Thank you for the suggestions, I was trying to avoid the OCXO removal but I think that now it must be done. I was also playing with the idea of populating the connectors so an OCXO exchange could be easily made, this makes possible to try various oscillators. Meanwhile I has been probing and measuring a lot of points and by chance I found a very interesting thing: Probing TP33 (which is close to the Trimble chip (U2) and directly connected to pin 76) there is a 1PPS, 10 us wide signal. I've checked it and appears to be synchronous with the 1/2 PPS output so maybe it can be routed to an output, probably I'll replace the 1/2 PPS with it, using the existing drive circuit and connector since it is very straightforward. My only concern is if this signal only is there during the anomalous condition that I have now, I have to retest it after fixing it. I had asked several times if anybody had located a 1PPS signal on these units, but the responses were negative and I had not probed systematically the board before. Also I'm taking notes of the signals found and I'll try to make a partial schematic at least with the EFC circuitry. When I fix it I'll clean the notes and figures and I'll upload it to some place. Best regards, Ignacio El 12/11/2014 a las 11:47, GandalfG8--- via time-nuts escribió: Hi Ignacio I have removed a faulty oscillator from one of these, not one of my more relaxed moments and quite amazed when the board emerged totally undamaged, but proof at least that it can be done:-) With the oscillator removed there's access to two sets of connector pads that will either accept SMA or SMB connectors and after conducting tests on the original oscillator via flying leads just soldered to the board I decided not to fit a replacement to the board after all but to fit a couple of SMB connectors to make the setup more versatile, and to avoid the possibility of having to remove another oscillator in the future:-) Another advantage of these pads is that if the board does get damaged removing the oscillator they can still be used as an alternative. The
Re: [time-nuts] My NTGS50AA failed
Hi Ignacio I'm sure removing the oscillator would make your faultfinding much more straightforward. When I removed mine I started out quite convinced I wouldn't be able to do it, even with the solder mostly removed from around the pins they were obviously quite a tight fit and all I had available at that time was a plunger type solder sucker and desoldering braid, as the bits on my old Pace desoldering kit were well past their best. The answer basically was lots of braid, lots of patience, and resisting like crazy any temptation to pull against a hole that wasn't fully released, but I certainly wouldn't want to do it that way again in a hurry. The desoldering gun I use now would make it easier but the holes are really a bit small for those oscillator pins. The good news though is that the connectors are there as a back up and fitting them definitely makes it more versatile. I had considered repeating the performance on another NTGS50AA and/or NTBW50AA, I really think I should but so far haven't found the courage:-) I think previous checks for 1PPS outputs might have been limited to the external connectors but it would make sense if it was available somewhere on the PCB, I'll try to get one powered up later and check your findings, if I can find a bit of space that us amongst the usual chaos! Regards Nigel GM8PZR In a message dated 13/11/2014 01:11:30 GMT Standard Time, eb4...@cembreros.jazztel.es writes: Hi Nigel, Thank you for the suggestions, I was trying to avoid the OCXO removal but I think that now it must be done. I was also playing with the idea of populating the connectors so an OCXO exchange could be easily made, this makes possible to try various oscillators. Meanwhile I has been probing and measuring a lot of points and by chance I found a very interesting thing: Probing TP33 (which is close to the Trimble chip (U2) and directly connected to pin 76) there is a 1PPS, 10 us wide signal. I've checked it and appears to be synchronous with the 1/2 PPS output so maybe it can be routed to an output, probably I'll replace the 1/2 PPS with it, using the existing drive circuit and connector since it is very straightforward. My only concern is if this signal only is there during the anomalous condition that I have now, I have to retest it after fixing it. I had asked several times if anybody had located a 1PPS signal on these units, but the responses were negative and I had not probed systematically the board before. Also I'm taking notes of the signals found and I'll try to make a partial schematic at least with the EFC circuitry. When I fix it I'll clean the notes and figures and I'll upload it to some place. Best regards, Ignacio El 12/11/2014 a las 11:47, GandalfG8--- via time-nuts escribió: Hi Ignacio I have removed a faulty oscillator from one of these, not one of my more relaxed moments and quite amazed when the board emerged totally undamaged, but proof at least that it can be done:-) With the oscillator removed there's access to two sets of connector pads that will either accept SMA or SMB connectors and after conducting tests on the original oscillator via flying leads just soldered to the board I decided not to fit a replacement to the board after all but to fit a couple of SMB connectors to make the setup more versatile, and to avoid the possibility of having to remove another oscillator in the future:-) Another advantage of these pads is that if the board does get damaged removing the oscillator they can still be used as an alternative. The connectors take the 10MHz from the oscillator into the board and the EFC control voltage out from the board to the oscillator, now there's a surprise:-), and oscillator power can be completely external if required. From this it would seem that the reference supply from the oscillator itself is not used in practice, certainly not in the offboard case anyway. As others have suggested it seems likely your problem may not be the oscillator itself, but it still might be worth removing anyway to make testing and fault finding more straightforward. The maximum positive excursion of the NTGS50AA should be 6 volts, not 5 as you're seeing, and another indication it might be worth removing the oscillator to see how the board behaves stand alone. I've not seen what seemed to be the repeated attempts at lock that you mentioned previously, but then I wasn't even aware for a long time that the control voltage could drive below 3 volts as well as above it:-) This is my note from previous observation of my faulty unit - When first powered it brings up all LEDs and then switches to a green LED for a few seconds and then amber. It starts a self survey and acquisition process with all appearing ok, and the DAC voltage reported
Re: [time-nuts] My NTGS50AA failed
Hello Nigel, Finally I got enough courage and removed the OCXO, you know what kind of task it is.. Fortunately I didn't spoiled the PCB so I'll install 2 smb connectors in the provided places, I don't want to return there if I need to change the oscillator. Well, the oscillator is ok, this is in some way bad news because the oscillator is easily replaceable, and the EFC voltage remains stuck on 5.02 V. Now I'll test the quad op-amp and the related parts. If they are ok the problem is in the Xilinx chip, something that cannot be replaced unless I get parts donor, even that way is very problematic since it is a 80 pin chip. I'll continue posting my findings. Best regards, Ignacio El 13/11/2014 a las 12:03, GandalfG8--- via time-nuts escribió: Hi Ignacio I'm sure removing the oscillator would make your faultfinding much more straightforward. When I removed mine I started out quite convinced I wouldn't be able to do it, even with the solder mostly removed from around the pins they were obviously quite a tight fit and all I had available at that time was a plunger type solder sucker and desoldering braid, as the bits on my old Pace desoldering kit were well past their best. The answer basically was lots of braid, lots of patience, and resisting like crazy any temptation to pull against a hole that wasn't fully released, but I certainly wouldn't want to do it that way again in a hurry. The desoldering gun I use now would make it easier but the holes are really a bit small for those oscillator pins. The good news though is that the connectors are there as a back up and fitting them definitely makes it more versatile. I had considered repeating the performance on another NTGS50AA and/or NTBW50AA, I really think I should but so far haven't found the courage:-) I think previous checks for 1PPS outputs might have been limited to the external connectors but it would make sense if it was available somewhere on the PCB, I'll try to get one powered up later and check your findings, if I can find a bit of space that us amongst the usual chaos! Regards Nigel GM8PZR In a message dated 13/11/2014 01:11:30 GMT Standard Time, eb4...@cembreros.jazztel.es writes: Hi Nigel, Thank you for the suggestions, I was trying to avoid the OCXO removal but I think that now it must be done. I was also playing with the idea of populating the connectors so an OCXO exchange could be easily made, this makes possible to try various oscillators. Meanwhile I has been probing and measuring a lot of points and by chance I found a very interesting thing: Probing TP33 (which is close to the Trimble chip (U2) and directly connected to pin 76) there is a 1PPS, 10 us wide signal. I've checked it and appears to be synchronous with the 1/2 PPS output so maybe it can be routed to an output, probably I'll replace the 1/2 PPS with it, using the existing drive circuit and connector since it is very straightforward. My only concern is if this signal only is there during the anomalous condition that I have now, I have to retest it after fixing it. I had asked several times if anybody had located a 1PPS signal on these units, but the responses were negative and I had not probed systematically the board before. Also I'm taking notes of the signals found and I'll try to make a partial schematic at least with the EFC circuitry. When I fix it I'll clean the notes and figures and I'll upload it to some place. Best regards, Ignacio El 12/11/2014 a las 11:47, GandalfG8--- via time-nuts escribió: Hi Ignacio I have removed a faulty oscillator from one of these, not one of my more relaxed moments and quite amazed when the board emerged totally undamaged, but proof at least that it can be done:-) With the oscillator removed there's access to two sets of connector pads that will either accept SMA or SMB connectors and after conducting tests on the original oscillator via flying leads just soldered to the board I decided not to fit a replacement to the board after all but to fit a couple of SMB connectors to make the setup more versatile, and to avoid the possibility of having to remove another oscillator in the future:-) Another advantage of these pads is that if the board does get damaged removing the oscillator they can still be used as an alternative. The connectors take the 10MHz from the oscillator into the board and the EFC control voltage out from the board to the oscillator, now there's a surprise:-), and oscillator power can be completely external if required. From this it would seem that the reference supply from the oscillator itself is not used in practice, certainly not in the offboard case anyway. As others have suggested it seems likely your problem may not be the oscillator itself, but it still might be worth removing anyway to make testing and fault finding more straightforward. The maximum positive excursion of
Re: [time-nuts] My NTGS50AA failed
Hi Ignacio I have removed a faulty oscillator from one of these, not one of my more relaxed moments and quite amazed when the board emerged totally undamaged, but proof at least that it can be done:-) With the oscillator removed there's access to two sets of connector pads that will either accept SMA or SMB connectors and after conducting tests on the original oscillator via flying leads just soldered to the board I decided not to fit a replacement to the board after all but to fit a couple of SMB connectors to make the setup more versatile, and to avoid the possibility of having to remove another oscillator in the future:-) Another advantage of these pads is that if the board does get damaged removing the oscillator they can still be used as an alternative. The connectors take the 10MHz from the oscillator into the board and the EFC control voltage out from the board to the oscillator, now there's a surprise:-), and oscillator power can be completely external if required. From this it would seem that the reference supply from the oscillator itself is not used in practice, certainly not in the offboard case anyway. As others have suggested it seems likely your problem may not be the oscillator itself, but it still might be worth removing anyway to make testing and fault finding more straightforward. The maximum positive excursion of the NTGS50AA should be 6 volts, not 5 as you're seeing, and another indication it might be worth removing the oscillator to see how the board behaves stand alone. I've not seen what seemed to be the repeated attempts at lock that you mentioned previously, but then I wasn't even aware for a long time that the control voltage could drive below 3 volts as well as above it:-) This is my note from previous observation of my faulty unit - When first powered it brings up all LEDs and then switches to a green LED for a few seconds and then amber. It starts a self survey and acquisition process with all appearing ok, and the DAC voltage reported as 3.02 volts. Sometime later, I've seen as short as 6 minutes but as long as 12 to 15 depending on how long the oscillator has been turned off and allowed to cool, once enough satellites are being tracked, the DAC voltage starts to increase, presumably seeking to drive the oscillator frequency to 10MHz, but the frequency doesn't reach 10MHz and the DAC voltage ramps up to 6.04 volts over a period of approx 30 seconds where it remains. As the DAC voltage crosses approx 5.6 volts the Red fault LED is switched on, as opposed to green that would normally be expected to indicate all was well, and Lady Heather's OSC: report switches from Good to Bad and highlights red. Similarly Normal OSC age changes to OSC age alarm and also highlights red. --- I've attached a Lady H plot that shows this, hopefully it will get through OK. The above DAC voltages were as reported by Lady Heather but I've checked these and, when the board is working as it should be anyway, they're very close. In my case the problem described above was an oscillator that had aged beyond the upper 6 volt limit, needing approx 6.54 volts to reach 10MHz, and once removed from the board I was able to add a simple op amp level shifter to bring it back into range just to prove all else was ok, which it was, but obviously Lady H now indicated the EFC into the level shifter rather than at the oscillator itself. Whilst your problem sounds like it might not be quite such an obvious fix, removing the oscillator would open the loop and make testing both the oscillator and the board much easier, so much as it's a pain I do feel that's probably your best next step. Regards Nigel GM8PZR In a message dated 12/11/2014 02:06:54 GMT Standard Time, eb4...@cembreros.jazztel.es writes: Hi, Removing the oscillator for testing and replacing it with other if it was the culprit was my first option. I have a spare Trimble oscillator that probably came from other NTGS50AA since it still have the foam band attached, but this oscillator is really aged, it needs 7.91 V to bring it on spot and the maximum control voltage of the NTGS50AA is 5 V. I was trying to avoid removing the oscillator but probably it must be done to clarify things. Thank you, Ignacio EB4APL . El 12/11/2014 a las 2:40, Mark Sims escribió: I have seen this caused by the oscillator not responding to the EFC signal. Fixed it by swapping in a MV-89 oscillator. The oscillators used in these units don't output an oven temperature monitor signal. ___ 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
Re: [time-nuts] My NTGS50AA failed
Charles, Thank you, I found this very enlightening. Now I have to find the 9.7 KHz pulses, no luck so far. Best regards, Ignacio El 12/11/2014 a las 7:34, Charles Steinmetz escribió: Ignacio wrote: I'm not very sure that the DAC is working, I suppose that the unit doesn't measure the DAC output, it reports the DAC commands. My voltage figures is what LH reports (so the NTGS50AA reports, probably what it is trying to do), but the frequency control pin of the oscillator is stuck at 5.02 V regardless of the supposed (intended) DAC output, it does not move at all. One more thing that could be helpful -- on Nov. 2, 2013 Stewart Cobb posted a description of the DAC operation for a Trimble Thunderbolt (Thunderbolt tuning DAC theory of operation). On Jan. 5, 2014 someone (no name) posted further information on the same thread re: the Trimble/Nortel 45k. You can find both posts in the list archives (follow the link at the bottom of this post, then click time-nuts Archives on the list home page). Best regards, Charles ___ 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] My NTGS50AA failed
Hi Nigel, Thank you for the suggestions, I was trying to avoid the OCXO removal but I think that now it must be done. I was also playing with the idea of populating the connectors so an OCXO exchange could be easily made, this makes possible to try various oscillators. Meanwhile I has been probing and measuring a lot of points and by chance I found a very interesting thing: Probing TP33 (which is close to the Trimble chip (U2) and directly connected to pin 76) there is a 1PPS, 10 us wide signal. I've checked it and appears to be synchronous with the 1/2 PPS output so maybe it can be routed to an output, probably I'll replace the 1/2 PPS with it, using the existing drive circuit and connector since it is very straightforward. My only concern is if this signal only is there during the anomalous condition that I have now, I have to retest it after fixing it. I had asked several times if anybody had located a 1PPS signal on these units, but the responses were negative and I had not probed systematically the board before. Also I'm taking notes of the signals found and I'll try to make a partial schematic at least with the EFC circuitry. When I fix it I'll clean the notes and figures and I'll upload it to some place. Best regards, Ignacio El 12/11/2014 a las 11:47, GandalfG8--- via time-nuts escribió: Hi Ignacio I have removed a faulty oscillator from one of these, not one of my more relaxed moments and quite amazed when the board emerged totally undamaged, but proof at least that it can be done:-) With the oscillator removed there's access to two sets of connector pads that will either accept SMA or SMB connectors and after conducting tests on the original oscillator via flying leads just soldered to the board I decided not to fit a replacement to the board after all but to fit a couple of SMB connectors to make the setup more versatile, and to avoid the possibility of having to remove another oscillator in the future:-) Another advantage of these pads is that if the board does get damaged removing the oscillator they can still be used as an alternative. The connectors take the 10MHz from the oscillator into the board and the EFC control voltage out from the board to the oscillator, now there's a surprise:-), and oscillator power can be completely external if required. From this it would seem that the reference supply from the oscillator itself is not used in practice, certainly not in the offboard case anyway. As others have suggested it seems likely your problem may not be the oscillator itself, but it still might be worth removing anyway to make testing and fault finding more straightforward. The maximum positive excursion of the NTGS50AA should be 6 volts, not 5 as you're seeing, and another indication it might be worth removing the oscillator to see how the board behaves stand alone. I've not seen what seemed to be the repeated attempts at lock that you mentioned previously, but then I wasn't even aware for a long time that the control voltage could drive below 3 volts as well as above it:-) This is my note from previous observation of my faulty unit - When first powered it brings up all LEDs and then switches to a green LED for a few seconds and then amber. It starts a self survey and acquisition process with all appearing ok, and the DAC voltage reported as 3.02 volts. Sometime later, I've seen as short as 6 minutes but as long as 12 to 15 depending on how long the oscillator has been turned off and allowed to cool, once enough satellites are being tracked, the DAC voltage starts to increase, presumably seeking to drive the oscillator frequency to 10MHz, but the frequency doesn't reach 10MHz and the DAC voltage ramps up to 6.04 volts over a period of approx 30 seconds where it remains. As the DAC voltage crosses approx 5.6 volts the Red fault LED is switched on, as opposed to green that would normally be expected to indicate all was well, and Lady Heather's OSC: report switches from Good to Bad and highlights red. Similarly Normal OSC age changes to OSC age alarm and also highlights red. --- I've attached a Lady H plot that shows this, hopefully it will get through OK. The above DAC voltages were as reported by Lady Heather but I've checked these and, when the board is working as it should be anyway, they're very close. In my case the problem described above was an oscillator that had aged beyond the upper 6 volt limit, needing approx 6.54 volts to reach 10MHz, and once removed from the board I was able to add a simple op amp level shifter to bring it back into range just to prove all else was ok, which it was, but obviously Lady H now indicated the EFC into the level shifter rather than at the oscillator itself. Whilst your problem sounds like it might not be quite such an obvious
Re: [time-nuts] My NTGS50AA failed
Hi It seems reasonable that there is a 1 pps somewhere on the board. The big question is if it’s the output of the GPS receiver or the output of the OCXO after division. Bob On Nov 12, 2014, at 8:10 PM, EB4APL eb4...@cembreros.jazztel.es wrote: Hi Nigel, Thank you for the suggestions, I was trying to avoid the OCXO removal but I think that now it must be done. I was also playing with the idea of populating the connectors so an OCXO exchange could be easily made, this makes possible to try various oscillators. Meanwhile I has been probing and measuring a lot of points and by chance I found a very interesting thing: Probing TP33 (which is close to the Trimble chip (U2) and directly connected to pin 76) there is a 1PPS, 10 us wide signal. I've checked it and appears to be synchronous with the 1/2 PPS output so maybe it can be routed to an output, probably I'll replace the 1/2 PPS with it, using the existing drive circuit and connector since it is very straightforward. My only concern is if this signal only is there during the anomalous condition that I have now, I have to retest it after fixing it. I had asked several times if anybody had located a 1PPS signal on these units, but the responses were negative and I had not probed systematically the board before. Also I'm taking notes of the signals found and I'll try to make a partial schematic at least with the EFC circuitry. When I fix it I'll clean the notes and figures and I'll upload it to some place. Best regards, Ignacio El 12/11/2014 a las 11:47, GandalfG8--- via time-nuts escribió: Hi Ignacio I have removed a faulty oscillator from one of these, not one of my more relaxed moments and quite amazed when the board emerged totally undamaged, but proof at least that it can be done:-) With the oscillator removed there's access to two sets of connector pads that will either accept SMA or SMB connectors and after conducting tests on the original oscillator via flying leads just soldered to the board I decided not to fit a replacement to the board after all but to fit a couple of SMB connectors to make the setup more versatile, and to avoid the possibility of having to remove another oscillator in the future:-) Another advantage of these pads is that if the board does get damaged removing the oscillator they can still be used as an alternative. The connectors take the 10MHz from the oscillator into the board and the EFC control voltage out from the board to the oscillator, now there's a surprise:-), and oscillator power can be completely external if required. From this it would seem that the reference supply from the oscillator itself is not used in practice, certainly not in the offboard case anyway. As others have suggested it seems likely your problem may not be the oscillator itself, but it still might be worth removing anyway to make testing and fault finding more straightforward. The maximum positive excursion of the NTGS50AA should be 6 volts, not 5 as you're seeing, and another indication it might be worth removing the oscillator to see how the board behaves stand alone. I've not seen what seemed to be the repeated attempts at lock that you mentioned previously, but then I wasn't even aware for a long time that the control voltage could drive below 3 volts as well as above it:-) This is my note from previous observation of my faulty unit - When first powered it brings up all LEDs and then switches to a green LED for a few seconds and then amber. It starts a self survey and acquisition process with all appearing ok, and the DAC voltage reported as 3.02 volts. Sometime later, I've seen as short as 6 minutes but as long as 12 to 15 depending on how long the oscillator has been turned off and allowed to cool, once enough satellites are being tracked, the DAC voltage starts to increase, presumably seeking to drive the oscillator frequency to 10MHz, but the frequency doesn't reach 10MHz and the DAC voltage ramps up to 6.04 volts over a period of approx 30 seconds where it remains. As the DAC voltage crosses approx 5.6 volts the Red fault LED is switched on, as opposed to green that would normally be expected to indicate all was well, and Lady Heather's OSC: report switches from Good to Bad and highlights red. Similarly Normal OSC age changes to OSC age alarm and also highlights red. --- I've attached a Lady H plot that shows this, hopefully it will get through OK. The above DAC voltages were as reported by Lady Heather but I've checked these and, when the board is working as it should be anyway, they're very close. In my case the problem described above was an oscillator that had aged beyond the upper 6 volt limit, needing approx 6.54 volts to reach 10MHz, and once removed from
[time-nuts] My NTGS50AA failed
Hello, After 2 yeses of continuous operation my NTGS50AA turned its red led on and stopped working. A check with LH shows OSC: BAD and OSC age alarm assuming that the oscillator had aged too much. I didn't believe this because when working, the DAC control voltage was around 2.9 V, in fact near the middle of its range (0-5 V). Measuring the 10 MHz output it is high, about 4.46 Hz which agrees with the LH figures. I measured the oscillator EFC pin and it is struck at 5.02 V, not following the DAC voltages as reported by LH. I think that either the DAC is bad or an amplifier after it. Since I don't have any schematic and the oscillator covers the top layer the troubleshooting is difficult. Has anybody experienced this failure before?. Does anybody has an schematic, even a partial one? Since the unit now is operating open loop I observed the locking strategy of this GPSDO. First it waits about 12 minutes for warming (I don't know if it internally monitors the oven current or uses a fixed time). During this period it sets the DAC output to the initial value as stored in the EEPROM (3.0 V). When it thinks that it is warmed enough, the DAC is ramped in the right direction to intercept exactly 10 MHz (towards 0 in my case). If it reaches 0 then declares the alarm and the DAC voltage is set to half the initial value (1.5 V). Five minutes later it switch the DAC to 2,25 V and 17 seconds later it returns to 1.5 V and remains there for 4 min and a half. Then it goes up again to 2.5 V and after 10 seconds it goes down to 1.88 V and after some 14 minutes it goes down again to 1.5 V, it remains there for about 15 minutes and then it goes down to 1.14 V, remains there for 80 seconds and goes back to 2.5 V. It looks like it checks from time to time if it is able to control the oscillator or simply it does weird things once it thinks that the oscillator cannot be disciplined. I will appreciate very much any information.that can help my troubleshooting. These units has more than doubled its price since I bought mine and I think that they are vanishing. The Guatemala's cell towers scrap has been exhausted. Regards, Ignacio EB4APL ___ 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] My NTGS50AA failed
Hi Ok, the gizmo you have is pretty similar to a Thunderbolt in terms of what they did for circuits. It’s by no means identical and I have not traced either one out far enough to have a schematic. At least from the TBolt - your DAC is working. The voltage is moving around and it’s getting low enough to bring the oscillator into lock. That suggests that the problem is not the DAC it’s self. I’d bet that what ever magic they do to figure out the oscillator frequency has gone nuts. A very common approach is to use the GPS PPS like a gate on a frequency counter. I think that this part gets a bit more fancy than that. Either way, that sounds like where the problem lies. Just in case - always check the regulated power supply voltages on the board and touch test the bypass caps. It’s a silly thing, but it doesn’t take long to do. I know I have gone for a few hours / days / weeks on something like this, only to finally bump into the shorted bypass cap or dead regulator and go “h…..”. Bob On Nov 11, 2014, at 8:07 PM, EB4APL eb4...@cembreros.jazztel.es wrote: Hello, After 2 yeses of continuous operation my NTGS50AA turned its red led on and stopped working. A check with LH shows OSC: BAD and OSC age alarm assuming that the oscillator had aged too much. I didn't believe this because when working, the DAC control voltage was around 2.9 V, in fact near the middle of its range (0-5 V). Measuring the 10 MHz output it is high, about 4.46 Hz which agrees with the LH figures. I measured the oscillator EFC pin and it is struck at 5.02 V, not following the DAC voltages as reported by LH. I think that either the DAC is bad or an amplifier after it. Since I don't have any schematic and the oscillator covers the top layer the troubleshooting is difficult. Has anybody experienced this failure before?. Does anybody has an schematic, even a partial one? Since the unit now is operating open loop I observed the locking strategy of this GPSDO. First it waits about 12 minutes for warming (I don't know if it internally monitors the oven current or uses a fixed time). During this period it sets the DAC output to the initial value as stored in the EEPROM (3.0 V). When it thinks that it is warmed enough, the DAC is ramped in the right direction to intercept exactly 10 MHz (towards 0 in my case). If it reaches 0 then declares the alarm and the DAC voltage is set to half the initial value (1.5 V). Five minutes later it switch the DAC to 2,25 V and 17 seconds later it returns to 1.5 V and remains there for 4 min and a half. Then it goes up again to 2.5 V and after 10 seconds it goes down to 1.88 V and after some 14 minutes it goes down again to 1.5 V, it remains there for about 15 minutes and then it goes down to 1.14 V, remains there for 80 seconds and goes back to 2.5 V. It looks like it checks from time to time if it is able to control the oscillator or simply it does weird things once it thinks that the oscillator cannot be disciplined. I will appreciate very much any information.that can help my troubleshooting. These units has more than doubled its price since I bought mine and I think that they are vanishing. The Guatemala's cell towers scrap has been exhausted. Regards, Ignacio EB4APL ___ 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] My NTGS50AA failed
I have seen this caused by the oscillator not responding to the EFC signal. Fixed it by swapping in a MV-89 oscillator. The oscillators used in these units don't output an oven temperature monitor signal. ___ 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] My NTGS50AA failed
Hi, I meant 2 years, it is quite late here. I'm not very sure that the DAC is working, I suppose that the unit doesn't measure the DAC output, it reports the DAC commands. My voltage figures is what LH reports (so the NTGS50AA reports, probably what it is trying to do), but the frequency control pin of the oscillator is stuck at 5.02 V regardless of the supposed (intended) DAC output, it does not move at all. I have checked the internal power supply voltages and they are ok. Hopefully a capacitor could be shorted to the +5V line but it looks too much luck for me. Thank you for your suggestions, Ignacio EB4APL On 12/11/2014 a las 2:23, Bob Camp wrote: Hi Ok, the gizmo you have is pretty similar to a Thunderbolt in terms of what they did for circuits. It’s by no means identical and I have not traced either one out far enough to have a schematic. At least from the TBolt - your DAC is working. The voltage is moving around and it’s getting low enough to bring the oscillator into lock. That suggests that the problem is not the DAC it’s self. I’d bet that what ever magic they do to figure out the oscillator frequency has gone nuts. A very common approach is to use the GPS PPS like a gate on a frequency counter. I think that this part gets a bit more fancy than that. Either way, that sounds like where the problem lies. Just in case - always check the regulated power supply voltages on the board and touch test the bypass caps. It’s a silly thing, but it doesn’t take long to do. I know I have gone for a few hours / days / weeks on something like this, only to finally bump into the shorted bypass cap or dead regulator and go “h…..”. Bob On Nov 11, 2014, at 8:07 PM, EB4APL eb4...@cembreros.jazztel.es wrote: Hello, After 2 yeses of continuous operation my NTGS50AA turned its red led on and stopped working. A check with LH shows OSC: BAD and OSC age alarm assuming that the oscillator had aged too much. I didn't believe this because when working, the DAC control voltage was around 2.9 V, in fact near the middle of its range (0-5 V). Measuring the 10 MHz output it is high, about 4.46 Hz which agrees with the LH figures. I measured the oscillator EFC pin and it is struck at 5.02 V, not following the DAC voltages as reported by LH. I think that either the DAC is bad or an amplifier after it. Since I don't have any schematic and the oscillator covers the top layer the troubleshooting is difficult. Has anybody experienced this failure before?. Does anybody has an schematic, even a partial one? Since the unit now is operating open loop I observed the locking strategy of this GPSDO. First it waits about 12 minutes for warming (I don't know if it internally monitors the oven current or uses a fixed time). During this period it sets the DAC output to the initial value as stored in the EEPROM (3.0 V). When it thinks that it is warmed enough, the DAC is ramped in the right direction to intercept exactly 10 MHz (towards 0 in my case). If it reaches 0 then declares the alarm and the DAC voltage is set to half the initial value (1.5 V). Five minutes later it switch the DAC to 2,25 V and 17 seconds later it returns to 1.5 V and remains there for 4 min and a half. Then it goes up again to 2.5 V and after 10 seconds it goes down to 1.88 V and after some 14 minutes it goes down again to 1.5 V, it remains there for about 15 minutes and then it goes down to 1.14 V, remains there for 80 seconds and goes back to 2.5 V. It looks like it checks from time to time if it is able to control the oscillator or simply it does weird things once it thinks that the oscillator cannot be disciplined. I will appreciate very much any information.that can help my troubleshooting. These units has more than doubled its price since I bought mine and I think that they are vanishing. The Guatemala's cell towers scrap has been exhausted. Regards, Ignacio EB4APL ___ 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] My NTGS50AA failed
Hi A .. I misunderstood what you were saying. As I now understand, the inputs to the DAC move around in the software, but the actual voltage out of the DAC is always stuck at 5V. The DAC (if it’s like a TBolt) is the sum of a set of signals into an op amp. There is a forest of metal film resistors and several amps in the setup. About the furthest I’ve gotten it to trace the signals past the first layer op amp and find that one of them is *way* off making the op amp rail. I’m sure that there is somebody who has taken that process further. It looks like a setup to sum several PWM outputs, but I could easily be wrong. Bob On Nov 11, 2014, at 8:47 PM, EB4APL eb4...@cembreros.jazztel.es wrote: Hi, I meant 2 years, it is quite late here. I'm not very sure that the DAC is working, I suppose that the unit doesn't measure the DAC output, it reports the DAC commands. My voltage figures is what LH reports (so the NTGS50AA reports, probably what it is trying to do), but the frequency control pin of the oscillator is stuck at 5.02 V regardless of the supposed (intended) DAC output, it does not move at all. I have checked the internal power supply voltages and they are ok. Hopefully a capacitor could be shorted to the +5V line but it looks too much luck for me. Thank you for your suggestions, Ignacio EB4APL On 12/11/2014 a las 2:23, Bob Camp wrote: Hi Ok, the gizmo you have is pretty similar to a Thunderbolt in terms of what they did for circuits. It’s by no means identical and I have not traced either one out far enough to have a schematic. At least from the TBolt - your DAC is working. The voltage is moving around and it’s getting low enough to bring the oscillator into lock. That suggests that the problem is not the DAC it’s self. I’d bet that what ever magic they do to figure out the oscillator frequency has gone nuts. A very common approach is to use the GPS PPS like a gate on a frequency counter. I think that this part gets a bit more fancy than that. Either way, that sounds like where the problem lies. Just in case - always check the regulated power supply voltages on the board and touch test the bypass caps. It’s a silly thing, but it doesn’t take long to do. I know I have gone for a few hours / days / weeks on something like this, only to finally bump into the shorted bypass cap or dead regulator and go “h…..”. Bob On Nov 11, 2014, at 8:07 PM, EB4APL eb4...@cembreros.jazztel.es wrote: Hello, After 2 yeses of continuous operation my NTGS50AA turned its red led on and stopped working. A check with LH shows OSC: BAD and OSC age alarm assuming that the oscillator had aged too much. I didn't believe this because when working, the DAC control voltage was around 2.9 V, in fact near the middle of its range (0-5 V). Measuring the 10 MHz output it is high, about 4.46 Hz which agrees with the LH figures. I measured the oscillator EFC pin and it is struck at 5.02 V, not following the DAC voltages as reported by LH. I think that either the DAC is bad or an amplifier after it. Since I don't have any schematic and the oscillator covers the top layer the troubleshooting is difficult. Has anybody experienced this failure before?. Does anybody has an schematic, even a partial one? Since the unit now is operating open loop I observed the locking strategy of this GPSDO. First it waits about 12 minutes for warming (I don't know if it internally monitors the oven current or uses a fixed time). During this period it sets the DAC output to the initial value as stored in the EEPROM (3.0 V). When it thinks that it is warmed enough, the DAC is ramped in the right direction to intercept exactly 10 MHz (towards 0 in my case). If it reaches 0 then declares the alarm and the DAC voltage is set to half the initial value (1.5 V). Five minutes later it switch the DAC to 2,25 V and 17 seconds later it returns to 1.5 V and remains there for 4 min and a half. Then it goes up again to 2.5 V and after 10 seconds it goes down to 1.88 V and after some 14 minutes it goes down again to 1.5 V, it remains there for about 15 minutes and then it goes down to 1.14 V, remains there for 80 seconds and goes back to 2.5 V. It looks like it checks from time to time if it is able to control the oscillator or simply it does weird things once it thinks that the oscillator cannot be disciplined. I will appreciate very much any information.that can help my troubleshooting. These units has more than doubled its price since I bought mine and I think that they are vanishing. The Guatemala's cell towers scrap has been exhausted. Regards, Ignacio EB4APL ___ 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] My NTGS50AA failed
Hi, Removing the oscillator for testing and replacing it with other if it was the culprit was my first option. I have a spare Trimble oscillator that probably came from other NTGS50AA since it still have the foam band attached, but this oscillator is really aged, it needs 7.91 V to bring it on spot and the maximum control voltage of the NTGS50AA is 5 V. I was trying to avoid removing the oscillator but probably it must be done to clarify things. Thank you, Ignacio EB4APL . El 12/11/2014 a las 2:40, Mark Sims escribió: I have seen this caused by the oscillator not responding to the EFC signal. Fixed it by swapping in a MV-89 oscillator. The oscillators used in these units don't output an oven temperature monitor signal. ___ 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] My NTGS50AA failed
Hi, I found in the top side a quad op amp, a LT 1014, surrounded by your forest of resistors. The output of one of these op amps goes directly to the control voltage input. I'm in the right track. It is very late here, 03:15 AM so I must go to the bed. Working so late is a call for disasters ... Best regards, Ignacio EB4APL El 12/11/2014 a las 2:54, Bob Camp escribió: Hi A .. I misunderstood what you were saying. As I now understand, the inputs to the DAC move around in the software, but the actual voltage out of the DAC is always stuck at 5V. The DAC (if it’s like a TBolt) is the sum of a set of signals into an op amp. There is a forest of metal film resistors and several amps in the setup. About the furthest I’ve gotten it to trace the signals past the first layer op amp and find that one of them is *way* off making the op amp rail. I’m sure that there is somebody who has taken that process further. It looks like a setup to sum several PWM outputs, but I could easily be wrong. Bob On Nov 11, 2014, at 8:47 PM, EB4APL eb4...@cembreros.jazztel.es wrote: Hi, I meant 2 years, it is quite late here. I'm not very sure that the DAC is working, I suppose that the unit doesn't measure the DAC output, it reports the DAC commands. My voltage figures is what LH reports (so the NTGS50AA reports, probably what it is trying to do), but the frequency control pin of the oscillator is stuck at 5.02 V regardless of the supposed (intended) DAC output, it does not move at all. I have checked the internal power supply voltages and they are ok. Hopefully a capacitor could be shorted to the +5V line but it looks too much luck for me. Thank you for your suggestions, Ignacio EB4APL On 12/11/2014 a las 2:23, Bob Camp wrote: Hi Ok, the gizmo you have is pretty similar to a Thunderbolt in terms of what they did for circuits. It’s by no means identical and I have not traced either one out far enough to have a schematic. At least from the TBolt - your DAC is working. The voltage is moving around and it’s getting low enough to bring the oscillator into lock. That suggests that the problem is not the DAC it’s self. I’d bet that what ever magic they do to figure out the oscillator frequency has gone nuts. A very common approach is to use the GPS PPS like a gate on a frequency counter. I think that this part gets a bit more fancy than that. Either way, that sounds like where the problem lies. Just in case - always check the regulated power supply voltages on the board and touch test the bypass caps. It’s a silly thing, but it doesn’t take long to do. I know I have gone for a few hours / days / weeks on something like this, only to finally bump into the shorted bypass cap or dead regulator and go “h…..”. Bob On Nov 11, 2014, at 8:07 PM, EB4APL eb4...@cembreros.jazztel.es wrote: Hello, After 2 yeses of continuous operation my NTGS50AA turned its red led on and stopped working. A check with LH shows OSC: BAD and OSC age alarm assuming that the oscillator had aged too much. I didn't believe this because when working, the DAC control voltage was around 2.9 V, in fact near the middle of its range (0-5 V). Measuring the 10 MHz output it is high, about 4.46 Hz which agrees with the LH figures. I measured the oscillator EFC pin and it is struck at 5.02 V, not following the DAC voltages as reported by LH. I think that either the DAC is bad or an amplifier after it. Since I don't have any schematic and the oscillator covers the top layer the troubleshooting is difficult. Has anybody experienced this failure before?. Does anybody has an schematic, even a partial one? Since the unit now is operating open loop I observed the locking strategy of this GPSDO. First it waits about 12 minutes for warming (I don't know if it internally monitors the oven current or uses a fixed time). During this period it sets the DAC output to the initial value as stored in the EEPROM (3.0 V). When it thinks that it is warmed enough, the DAC is ramped in the right direction to intercept exactly 10 MHz (towards 0 in my case). If it reaches 0 then declares the alarm and the DAC voltage is set to half the initial value (1.5 V). Five minutes later it switch the DAC to 2,25 V and 17 seconds later it returns to 1.5 V and remains there for 4 min and a half. Then it goes up again to 2.5 V and after 10 seconds it goes down to 1.88 V and after some 14 minutes it goes down again to 1.5 V, it remains there for about 15 minutes and then it goes down to 1.14 V, remains there for 80 seconds and goes back to 2.5 V. It looks like it checks from time to time if it is able to control the oscillator or simply it does weird things once it thinks that the oscillator cannot be disciplined. I will appreciate very much any information.that can help my troubleshooting. These units has more than doubled its price since I bought mine and I think that they are vanishing. The Guatemala's cell towers scrap has
Re: [time-nuts] My NTGS50AA failed
Ignacio wrote: I'm not very sure that the DAC is working, I suppose that the unit doesn't measure the DAC output, it reports the DAC commands. My voltage figures is what LH reports (so the NTGS50AA reports, probably what it is trying to do), but the frequency control pin of the oscillator is stuck at 5.02 V regardless of the supposed (intended) DAC output, it does not move at all. I'm not sure I understand what you've measured. I take it you have measured the EFC pin on the OCXO, and it reads 5.02v? Have you also determined what the voltage is on the DAC output pin? (Are they connected directly together, or is there a resistor or other circuitry between them?) If they are both at 5.02v, you need to disconnect them and see which one is pulling the node to that voltage (it could be an internal failure in the OCXO). Best regards, Charles ___ 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] My NTGS50AA failed
Ignacio wrote: I'm not very sure that the DAC is working, I suppose that the unit doesn't measure the DAC output, it reports the DAC commands. My voltage figures is what LH reports (so the NTGS50AA reports, probably what it is trying to do), but the frequency control pin of the oscillator is stuck at 5.02 V regardless of the supposed (intended) DAC output, it does not move at all. One more thing that could be helpful -- on Nov. 2, 2013 Stewart Cobb posted a description of the DAC operation for a Trimble Thunderbolt (Thunderbolt tuning DAC theory of operation). On Jan. 5, 2014 someone (no name) posted further information on the same thread re: the Trimble/Nortel 45k. You can find both posts in the list archives (follow the link at the bottom of this post, then click time-nuts Archives on the list home page). Best regards, Charles ___ 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.
