Re: [time-nuts] KS-24361 Power Module Repair
That is almost a carbon copy description of how I fixed a similar module in my Ball/Efratom MGPS unit on my GPSRb unit. An oven set to 140C is your friend when doing jobs like this. The guys that make these modules are trying to make them as small as possible, so they always use tantalum capacitors, and run them very close to their ratings... in this case, it was 18V on a 20V cap. This particular module had +/- 15V, and +5V on board. I have never seen so many individual switching power supplies stuffed into a single module... They were all little 5 terminal IC's, with each running at whatever frequency it felt like... -Chuck Harris Bob Stewart wrote: This is just a brief report, not a how-to. I got a KS_24361 with a bad Lucent power module. Having nothing to lose I thought I'd see if it came apart. After unsoldering it from the motherboard, I found the usual potting compound. Fortunately, the compound was only loosely attached to the board in the brick and was easy to pick off. After that, I used a pair of needle-nose pliers to work the board out of the casing. In spite of the pic below, I first gently pried up on the corners, in succession, until the corners released. Then I worked my way toward the middle, until the board came out. Be aware that there are two small inductors on the top side of the board that have metal covers that will probably stay in the potting compound. Just leave them there. When you push it all back together the covers will go back on the inductors. http://evoria.net/AE6RV/KS/OpenUp.jpg One corner of the brick was pretty hot while I had it on, so I figured there was a shorted component. As it turned out, it was a 15uF tantalum cap with a big brown spot on it. http://evoria.net/AE6RV/KS/BadCap.jpg Here's the cap removed from the board at the upper left. http://evoria.net/AE6RV/KS/CapRemoved.jpg So, ordered the cap, put it on the board, then just pushed the pins into the motherboard for testing. I didn't even bother soldering it. http://evoria.net/AE6RV/KS/Testing.jpg Tests were good, so I stuffed the board back into the casing, and soldered it all back on the motherboard. I didn't bother repotting the bottom surface of the board. I attached the repaired KS to my good REF-0, and it's now working. Bob - AE6RV ___ 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] KS-24361 Power Module Repair
This is just a brief report, not a how-to. I got a KS_24361 with a bad Lucent power module. Having nothing to lose I thought I'd see if it came apart. After unsoldering it from the motherboard, I found the usual potting compound. Fortunately, the compound was only loosely attached to the board in the brick and was easy to pick off. After that, I used a pair of needle-nose pliers to work the board out of the casing. In spite of the pic below, I first gently pried up on the corners, in succession, until the corners released. Then I worked my way toward the middle, until the board came out. Be aware that there are two small inductors on the top side of the board that have metal covers that will probably stay in the potting compound. Just leave them there. When you push it all back together the covers will go back on the inductors. http://evoria.net/AE6RV/KS/OpenUp.jpg One corner of the brick was pretty hot while I had it on, so I figured there was a shorted component. As it turned out, it was a 15uF tantalum cap with a big brown spot on it. http://evoria.net/AE6RV/KS/BadCap.jpg Here's the cap removed from the board at the upper left. http://evoria.net/AE6RV/KS/CapRemoved.jpg So, ordered the cap, put it on the board, then just pushed the pins into the motherboard for testing. I didn't even bother soldering it. http://evoria.net/AE6RV/KS/Testing.jpg Tests were good, so I stuffed the board back into the casing, and soldered it all back on the motherboard. I didn't bother repotting the bottom surface of the board. I attached the repaired KS to my good REF-0, and it's now working. Bob - AE6RV ___ 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] Vintage Crystal Oven
Thanks George, I used to work in a Motorola 2-way shop. The only heated ovens that Motorola used were the 6.3V thermostatically controlled ovens. Those were used in the old tube-style units. When they went solid-state, they used TXCOs in both base and mobile units. However, I'll check them out. Never know, there might be something useful there. Cheers, Dave M George Dubovsky wrote: I'm not sure I remember the exact one you are describing, but in the last month or so, there was a fellow selling crystal ovens on QTH.com. I think they were from land-mobile service, like Motorola base stations or some such. That's another place to search. 73, geo - n4ua On Fri, Apr 10, 2015 at 12:37 PM, Dave M wrote: Years ago, (70s maybe) I came across an empty crystal oven. I know I have it in one of the storage containers of old stuff in my garage, but I can't find it. It was a proportional oven, but was otherwise an empty shell, so you could put your own circuitry inside (oscillator, voltage reference, etc.). Several small wires came out of it for power, temperature adjustment, e.g. Physical size was in the neighborhood of 1.5x1.5x3 inches. As I remember, it was manufactured by one of the major crystal manufacturers of the day (e.g., Knight, Bliley, etc.) Does anyone remember these ovens? I'd surely like to get my hands on a couple or three to play with. I search the net & Ebay occasionally for them, but so far, no hits. Dave M ___ 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] Counter averaging errors near clock harmonics
The subject of errors in averaging counters at input frequencies near the clock frequency and its subharmonics and harmonics comes up on the list from time to time. There is a nice discussion of the phenomenon, and how it was addressed in the design of the HP 5345A counter, in the June, 1974 issue of the Hewlett-Packard Journal: David C. Chu, "Time Interval Averaging: Theory, Problems, and Solutions," HP Journal v25 n10, June 1974 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] Vintage Crystal Oven
I'm not sure I remember the exact one you are describing, but in the last month or so, there was a fellow selling crystal ovens on QTH.com. I think they were from land-mobile service, like Motorola base stations or some such. That's another place to search. 73, geo - n4ua On Fri, Apr 10, 2015 at 12:37 PM, Dave M wrote: > Years ago, (70s maybe) I came across an empty crystal oven. I know I have > it > in one of the storage containers of old stuff in my garage, but I can't > find > it. It was a proportional oven, but was otherwise an empty shell, so you > could put your own circuitry inside (oscillator, voltage reference, etc.). > Several small wires came out of it for power, temperature adjustment, e.g. > Physical size was in the neighborhood of 1.5x1.5x3 inches. > As I remember, it was manufactured by one of the major crystal > manufacturers > of the day (e.g., Knight, Bliley, etc.) > > Does anyone remember these ovens? I'd surely like to get my hands on a > couple or three to play with. I search the net & Ebay occasionally for > them, but so far, no hits. > > Dave M > ___ > 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] Mini-time lab cost and maintenance
Adam wrote (via tvb): I was thinking maybe something with an uncertainty of around 1e-9 or 1e-10. Are there simple quarts oscillators that are good enough for that or is more equipment necessary? Adam, your original post seemed to state a goal of having a "small and lower level time lab." Is a precision oscillator all you were thinking of (this would be sufficient to keep other clocked instruments, receivers, transmitters, and what not close to on frequency), or do you also want to do precision comparisons between the oscillator's output and other time and frequency signals, or precision time interval measurements, or to characterize the stability of other frequency sources to that level of precision? In any of the latter cases, you also need precision counter/timers, and depending on the particular task you may need signal conditioners, mixers, filters, and other paraphernalia (some of which you may need to build yourself). And as Tom pointed out, to be confident that your e-10 oscillator has not drifted beyond e-10, you will need some means of periodically comparing it to a better standard (which could be GPS or WWV, or a better local standard such as a cesium or hydrogen maser source). This will require some additional equipment (alternatively, you could send the oscillator away for calibration periodically). So, even with the clarification you sent to Tom, it is hard to advise you because you still haven't said what you are hoping to be able to do with your time lab. I would venture to say that at a minimum, you will need a precision oscillator and a counter/timer with more than ten digits of resolution. The counter/timers that come to my mind for a value-based home lab are the HP5345A, HP5370A or B, and the SRS SR620. The 5345 is very capable but is often overlooked by time-nuts, and probably offers the best value available -- but you need to wait 1000 seconds to get its maximum resolution. (There are others, but these three are, IMO, the best suited to the tasks most often performed in home labs. For example, the HP 5334A would need one or two more digits to be maximally useful at the limits usually pursued by time-nuts.) Note that these older counters will require some maintenance and may require repairs from time to time. 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.
