[time-nuts] troubleshooting a FE-5680A (got two; only one works)
Just yesterday I received two FE-5680A units from China. One of them works and one doesn't achieve lock. Both are labelled with FEI P/N 217400-30352-1. Here's a photo of the one that works, the other looks just the same but different serial number. https://picasaweb.google.com/109928236040342205185/FE5680A#5680473663653140162 FE-5680A Rb #1: At startup, RF out (pin 7) ramps from 9.999828 to 10.66 MHz for a few minutes, then locks at 10.00 MHz and pin 3 drops low. The RF signal is about 2 Vpp. Power draw at startup about 25 W, dropping to 10 W. FE-5680A Rb #2: RF out scans from 9.999799 to 9.94 MHz repeatedly, and does not achieve lock. Pin 3 remains high. The RF signal is about 1 Vpp (half the level of the working unit). Power draw similar to unit #1. Any suggestions for what might be done to prod the 2nd unit towards working? I see some things which might be trimmer caps on the board, and what might be a round heating element(?) soldered to a crystal can in this photo: https://picasaweb.google.com/lh/photo/0WRM10pGG0Kd89Ji80yoa9MTjNZETYmyPJy0liipFm0?feat=directlink thanks for any advice! John Beale N8JUF ___ 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] troubleshooting a FE-5680A (got two; only one works)
John, Instead of trying to fix it you should fault the unit back to seller and get a refund or have him send another unit. I would also attempt to get them to pay for the return shipping as well. After all it is their fault they sent a bad one when all of them are claiming that they are working correctly. As for troubleshooting, that is way easier said then done. These newer series of FE-5680's are much more digital in nature then the older design, which makes it much harder. The company that makes them is not and will not give out information. BillWB6BNQ John Beale wrote: Just yesterday I received two FE-5680A units from China. One of them works and one doesn't achieve lock. Both are labelled with FEI P/N 217400-30352-1. Here's a photo of the one that works, the other looks just the same but different serial number. https://picasaweb.google.com/109928236040342205185/FE5680A#5680473663653140162 FE-5680A Rb #1: At startup, RF out (pin 7) ramps from 9.999828 to 10.66 MHz for a few minutes, then locks at 10.00 MHz and pin 3 drops low. The RF signal is about 2 Vpp. Power draw at startup about 25 W, dropping to 10 W. FE-5680A Rb #2: RF out scans from 9.999799 to 9.94 MHz repeatedly, and does not achieve lock. Pin 3 remains high. The RF signal is about 1 Vpp (half the level of the working unit). Power draw similar to unit #1. Any suggestions for what might be done to prod the 2nd unit towards working? I see some things which might be trimmer caps on the board, and what might be a round heating element(?) soldered to a crystal can in this photo: https://picasaweb.google.com/lh/photo/0WRM10pGG0Kd89Ji80yoa9MTjNZETYmyPJy0liipFm0?feat=directlink thanks for any advice! John Beale N8JUF ___ 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] troubleshooting a FE-5680A (got two; only one works)
Try to re-initialize it. I think that it is possible to reset the unit. My LPFRS, for example, has two commands (F00, C00) to reset the fine and coarse tuning to the factory default. I have to read the FE5680A datasheet to confirm but generally digital units have factory defaults, resets, presets and so on. On Wed, Nov 30, 2011 at 10:26 AM, WB6BNQ wb6...@cox.net wrote: John, Instead of trying to fix it you should fault the unit back to seller and get a refund or have him send another unit. I would also attempt to get them to pay for the return shipping as well. After all it is their fault they sent a bad one when all of them are claiming that they are working correctly. As for troubleshooting, that is way easier said then done. These newer series of FE-5680's are much more digital in nature then the older design, which makes it much harder. The company that makes them is not and will not give out information. BillWB6BNQ John Beale wrote: Just yesterday I received two FE-5680A units from China. One of them works and one doesn't achieve lock. Both are labelled with FEI P/N 217400-30352-1. Here's a photo of the one that works, the other looks just the same but different serial number. https://picasaweb.google.com/109928236040342205185/FE5680A#5680473663653140162 FE-5680A Rb #1: At startup, RF out (pin 7) ramps from 9.999828 to 10.66 MHz for a few minutes, then locks at 10.00 MHz and pin 3 drops low. The RF signal is about 2 Vpp. Power draw at startup about 25 W, dropping to 10 W. FE-5680A Rb #2: RF out scans from 9.999799 to 9.94 MHz repeatedly, and does not achieve lock. Pin 3 remains high. The RF signal is about 1 Vpp (half the level of the working unit). Power draw similar to unit #1. Any suggestions for what might be done to prod the 2nd unit towards working? I see some things which might be trimmer caps on the board, and what might be a round heating element(?) soldered to a crystal can in this photo: https://picasaweb.google.com/lh/photo/0WRM10pGG0Kd89Ji80yoa9MTjNZETYmyPJy0liipFm0?feat=directlink thanks for any advice! John Beale N8JUF ___ 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] troubleshooting a FE-5680A (got two; only one works)
I tend to agree with this - but it looks like it's already been opened, which could cause problems. Some things you can quickly check are that the lamp housing and the Rb cell shielding are getting hot (use a thermometer, not your fingers!) and that the lamp is lit by checking for a purple glow at the back of the lamp housing. I suspect these are all OK, though, since the current consumption is about the same as the other one. One of my dead units had a bad 3.3V regulator (MAX882, on the back of the board - input is 5B on pin 5, output is 3.3V on pin 4) - since that 3,3V line runs the Xilinx PLD that divides down the clock and you have a low output signal, it sounds possible... If your supplies are good, try scoping the photocell testpoint - it's the one above and slightly to the right of the FPC going to the Rb cell assembly in your photo 4 of 8 - it should show a signal when the oscillator frequency sweeps through the Rb resonance frequency - if you can't see anything at all, then check to make sure that the VXCO is actually sweeping through 10MHz - if not, you can try adjusting C217 to centralise the sweep range. If if is going through 10MHz and there is no signal, check the drive to the snap diode on that little RF connector - you should see a 60MHz signal mixed with about 4.3MHz - if that looks good, and the there is still no signal at the photocell, suspect the physics package. Regards, Pete On Wed, Nov 30, 2011 at 5:26 PM, WB6BNQ wb6...@cox.net wrote: John, Instead of trying to fix it you should fault the unit back to seller and get a refund or have him send another unit. I would also attempt to get them to pay for the return shipping as well. After all it is their fault they sent a bad one when all of them are claiming that they are working correctly. As for troubleshooting, that is way easier said then done. These newer series of FE-5680's are much more digital in nature then the older design, which makes it much harder. The company that makes them is not and will not give out information. BillWB6BNQ John Beale wrote: Just yesterday I received two FE-5680A units from China. One of them works and one doesn't achieve lock. Both are labelled with FEI P/N 217400-30352-1. Here's a photo of the one that works, the other looks just the same but different serial number. https://picasaweb.google.com/109928236040342205185/FE5680A#5680473663653140162 FE-5680A Rb #1: At startup, RF out (pin 7) ramps from 9.999828 to 10.66 MHz for a few minutes, then locks at 10.00 MHz and pin 3 drops low. The RF signal is about 2 Vpp. Power draw at startup about 25 W, dropping to 10 W. FE-5680A Rb #2: RF out scans from 9.999799 to 9.94 MHz repeatedly, and does not achieve lock. Pin 3 remains high. The RF signal is about 1 Vpp (half the level of the working unit). Power draw similar to unit #1. Any suggestions for what might be done to prod the 2nd unit towards working? I see some things which might be trimmer caps on the board, and what might be a round heating element(?) soldered to a crystal can in this photo: https://picasaweb.google.com/lh/photo/0WRM10pGG0Kd89Ji80yoa9MTjNZETYmyPJy0liipFm0?feat=directlink thanks for any advice! John Beale N8JUF ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] troubleshooting a FE-5680A (got two; only one works)
I would just combine these recommendations - see if the local XO can be adjusted to lock. If so, problem solved. If not, then try to return and replace the unit. 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] troubleshooting a FE-5680A (got two; only one works)
Hi At this point I'd contact the seller. You know that the part has a problem and you have done enough checking to be sure it's nothing trivial (like a loose wire). The worst that can happen is he does not reply, the best is that he sends you another part for free. There are a number of possibilities in-between the two. At this point you have a pretty good case. Once you start twiddling this or that, you are not in as good a position. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of John Beale Sent: Wednesday, November 30, 2011 2:18 AM To: time-nuts@febo.com Subject: [time-nuts] troubleshooting a FE-5680A (got two; only one works) Just yesterday I received two FE-5680A units from China. One of them works and one doesn't achieve lock. Both are labelled with FEI P/N 217400-30352-1. Here's a photo of the one that works, the other looks just the same but different serial number. https://picasaweb.google.com/109928236040342205185/FE5680A#56804736636531401 62 FE-5680A Rb #1: At startup, RF out (pin 7) ramps from 9.999828 to 10.66 MHz for a few minutes, then locks at 10.00 MHz and pin 3 drops low. The RF signal is about 2 Vpp. Power draw at startup about 25 W, dropping to 10 W. FE-5680A Rb #2: RF out scans from 9.999799 to 9.94 MHz repeatedly, and does not achieve lock. Pin 3 remains high. The RF signal is about 1 Vpp (half the level of the working unit). Power draw similar to unit #1. Any suggestions for what might be done to prod the 2nd unit towards working? I see some things which might be trimmer caps on the board, and what might be a round heating element(?) soldered to a crystal can in this photo: https://picasaweb.google.com/lh/photo/0WRM10pGG0Kd89Ji80yoa9MTjNZETYmyPJy0li ipFm0?feat=directlink thanks for any advice! John Beale N8JUF ___ 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] troubleshooting a FE-5680A (got two; only one works)
[Peter Bell] ...check to make sure that the VXCO is actually sweeping through 10MHz - if not, you can try adjusting C217 to centralise the sweep range. Thanks Pete, you are exactly right. As mentioned, the VCXO was sweeping from 9.999799 to 9.94 MHz with no lock. I found that the C217 trimmer was nearly at minimum C already, but a tiny tweak to move it to absolute minimum C shifted up the center frequency 30 Hz, which (just) enabled a lock at 10.00 MHz. Given the pre-existing C217 setting, I wonder if this unit was marginal even from the factory. I don't know what minimum value C217 has, but I could remove C217 completely which might center it more. Or, maybe there is a way to increase the VCO tuning range, no doubt at a cost in phase noise. Asking for a replacement unit is another option, but I'm just too impatient for that, so I'm taking it as an opportunity to learn something. (in fact I did send him a note, but I'm not expecting anything.) Thanks to Pete and the time-nuts list for the solution! -john ___ 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] troubleshooting a FE-5680A (got two; only one works)
It does seem rather off frequency - the other thing that might be worth checking is to verify that the PTC thermistor soldered to the crystal is getting hot, since failure of that would seem likely to induce frequency errors of about that magnitude. Regards, Pete On Thu, Dec 1, 2011 at 2:01 AM, beale be...@bealecorner.com wrote: [Peter Bell] ...check to make sure that the VXCO is actually sweeping through 10MHz - if not, you can try adjusting C217 to centralise the sweep range. Thanks Pete, you are exactly right. As mentioned, the VCXO was sweeping from 9.999799 to 9.94 MHz with no lock. I found that the C217 trimmer was nearly at minimum C already, but a tiny tweak to move it to absolute minimum C shifted up the center frequency 30 Hz, which (just) enabled a lock at 10.00 MHz. Given the pre-existing C217 setting, I wonder if this unit was marginal even from the factory. I don't know what minimum value C217 has, but I could remove C217 completely which might center it more. Or, maybe there is a way to increase the VCO tuning range, no doubt at a cost in phase noise. Asking for a replacement unit is another option, but I'm just too impatient for that, so I'm taking it as an opportunity to learn something. (in fact I did send him a note, but I'm not expecting anything.) Thanks to Pete and the time-nuts list for the solution! -john ___ 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.
