Telcom upgrade, just like where all the Thuderbolts came from On Sun, Nov 13, 2011 at 9:21 AM, Chuck Forsberg WA7KGX N2469R <[email protected]> wrote: > Seems like a lot of folks selling these lately. > Curious minds would like to know why. > > On 11/13/2011 07:15 AM, [email protected] wrote: >> >> Pete >> That is exactly the same math I did, there is no other choice but it would >> be nice if some one can help on the C field. I just finished mounting it >> on >> a heat sink added a Toshiba 15 V 3 A power supply and a 7805 and will run >> it for a month with out changing any thing. Will read it twice a day and >> see how it behaves. >> Bert >> >> >> In a message dated 11/13/2011 9:24:47 A.M. Eastern Standard Time, >> [email protected] writes: >> >> Yes, I'm quite sure this is how it works - if you scope the snap diode >> drive you can quite clearly see both the 60MHz and the 5.3MHz from the >> DDS chip mixed together. My assumption is that the DDS output is >> subtractively mixed with the 114th harmonic of the 60Mhz inside the >> cavity: 60*114 = 6.840Ghz - ~5.3Mhz = ~6.8347 GHz clearly puts you in >> exactly the right ballpark. >> >> This would also explain the very fine tuning steps - a 1Hz change on >> the DDS output would only need a ~1.45mHz change of the unit output >> frequency (at 10MHz) to bring the loop back into lock. >> >> I still have the unit with the bad Rb cell in bits, so I will have a >> poke around it and see if I can figure out how the drive on the >> C-Field coil is derived. >> >> Regards, >> >> Pete >> >> >> >> >> On Sun, Nov 13, 2011 at 7:40 PM,<[email protected]> wrote: >>> >>> Pete >>> Thank you for your information. I agree with your findings and as I >> >> pointed >>> >>> out previously it support the math that the AD 9832 is used for tuning. >>> That allows them to set the Rb at the optimum operating point based on >> >> their >>> >>> gas mixture. What I like to know is how they control the C field. >> >> Again I >>> >>> think they picked an optimum point and only vary it slightly for >>> temperature compensation. I would like to use the C field to fine tune >> >> using a >>> >>> modified Shera controller. Latest voltage measurements on the C field >> >> across the >>> >>> coil are 2.5110 and 2.5238 down from 2.5134 and 2.5256. >>> Bert Kehren >>> >>> >>> In a message dated 11/13/2011 4:38:09 A.M. Eastern Standard Time, >>> [email protected] writes: >>> >>> I can let you know what I've found out about these units - I got given >>> a couple of dead ones and did a bit of poking around trying to get >>> them working. I didn't get that far, since one of the units was >>> easily fixed (the MAX882 3.3V regulator had failed) and the other >>> seems to have a faulty Rb absorption cell (it works if you swap the >>> cell from the other unit into it). >>> >>> The first is, as you noticed, that they have 3 voltage regulators - >>> but apparently couldn't spare one to generate the +5V line - they seem >>> to run (1) The Rb lamp / heater (the one nearest the connector) (2) >>> the cell heater (the middle one) and (3) the analog electronics @8.8V >>> (the last one). >>> >>> The quickest way to verify this is to apply +15V / GND to pins 1 and 2 >>> of the d-type and then check the voltage on the VCC pin (20) of the >>> 74ACT240 buffer chip next to the connector - there is no 5V there. >>> There is also no 5V on pin 5 of the MAX882 - and hence no 3.3V line. >>> >>> There is a connection between these points and pin 4 of the d-type - >>> and applying an external +5V to this pin will bring up the 3.3V line >>> and allow the unit to lock. When locked, pin 3 on the d-type goes >>> low, and will sink enough current to operate an LED. >>> >>> Pin 5 is also connected to GND, and was (on the original PCB) also >>> connected to the ground plane along with pin 2. It doesn't seem to be >>> actually necessary, as the unit will operate with a single ground >>> connection, but would it would seem to be good practice to use this >>> pin, too. >>> >>> It's been alleged that pin 6 is a 1PPS output - but I can't see >>> anything on it at all except a constant logic 1 - I tried changing the >>> 'ACT240 in case the buffer was damaged, but this had no effect, and >>> the pin is still a constant 1. I suppose it's possible that there is >>> an extremely narrow -ve going pulse on it, but if there is it's too >>> narrow for the trigger circuit on my (100MHz) scope to see it. >>> >>> Pin 7 outputs a 10MHz sine wave - about 800mV p-p unloaded. I haven't >>> put it into an analyzer, but it looks pretty good. >>> >>> Pin 8 and 9 are connected to the MAX3232 on the board, and from them >>> onto the serial port on the DS80C323 CPU. Pin 8 is RXD, pin 9 is TXD >>> (from the unit's point of view). This serial port accepts the commands >>> described in the FEI document that's floating around the net for >>> trimming the oscillator. They appear to operate as described. >>> >>> Internally, the main VXCO runs at 60MHz - it's buffered and fed into >>> the Xilinx XC9572XL PLD on the back of the board. This chip appears >>> to contain mostly frequency dividers - it generates the 10MHz output, >>> 20MHz for the MCLK to the DDS chip (although with a slightly nasty >>> 40:60 duty cycle) a 416.6666Hz drive for the fselect pin on the DDS >>> chip, a 833.33333Hz drive for the lock in amp. There are also a bunch >>> of signals that go to the test connector, and are presumably used for >>> factory programming. >>> >>> The output of the DDS is about 5.3MHz with FM on it at a 416.666Hz >>> rate - this is mixed in with the 60MHz output from the VCXO to give >>> the drive signal to the snap diode in the physics package. >>> >>> There are 3 pots on the board - the one that's normally accessible via >>> a hole in the case seems to be intended as a C-field adjust, but does >>> nothing on the units I have - the other one near it appears to trim >>> something in the photocell amplifier circuit. The one on the other >>> side of the board (near the VCXO) sets the bias on the snap diode >>> >>> That's all I've got, since I then worked out that I didn't have an >>> electronics problem - hope it helps. >>> >>> Regards, >>> >>> Pete Bell >>> >>> >>> On Sun, Nov 13, 2011 at 1:46 AM, Don Latham<[email protected]> wrote: >>>> >>>> I just bought a couple of 5680A's that have the same FEI p/n. They are >>>> pop-riveted to a heavy double-sided board., obviously cut off from a >>>> longer board. I've removed one of these from it's board/heatsink. >> >> There >>>> >>>> are two pots on the board, only one of them can be trimmed with the >> >> case >>>> >>>> on. The sinewave forming filter and maybe countdown chips are not >> >> there, >>>> >>>> and never were. There are three identical voltage regulators on the >>>> heatsink spine. >>>> I'll be doing some more reverse engineering on these units; they were >> >> so >>>> >>>> cheap I had to have a couple! If only FEI was more helpful! hey must >>>> have moved on from these, and could put one manual out there? >>>> Oh Well! >>>> Don >>>> >>>> [email protected] >>>>> >>>>> The FE 5680A's advertised as NEW are not NEW! A friend that made >>>>> me >>>>> aware of the sale did notice clear signs of use, so I did a closer >>>>> inspection >>>>> under a Microscope and found clear indications that the unit has >>>>> been >>>>> bolted down in the past. Does work fine and I am looking at ways to >>>>> go >>>>> directly >>>>> to the C field to disciplin the Rb. Does any one have info that would >>>>> help >>>>> to do so. >>>>> Bert Kehren Miami >>>>> _______________________________________________ >>>>> time-nuts mailing list -- [email protected] >>>>> To unsubscribe, go to >>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>> and follow the instructions there. >>>>> >>>> >>>> -- >>>> "Neither the voice of authority nor the weight of reason and argument >>>> are as significant as experiment, for thence comes quiet to the mind." >>>> R. Bacon >>>> "If you don't know what it is, don't poke it." >>>> Ghost in the Shell >>>> >>>> >>>> Dr. Don Latham AJ7LL >>>> Six Mile Systems LLP >>>> 17850 Six Mile Road >>>> POB 134 >>>> Huson, MT, 59846 >>>> VOX 406-626-4304 >>>> www.lightningforensics.com >>>> www.sixmilesystems.com >>>> >>>> >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>> >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> >>>> and follow the instructions there. >>>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >> >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> >>> and follow the instructions there. >>> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > -- > Chuck Forsberg WA7KGX N2469R [email protected] www.omen.com > Developer of Industrial ZMODEM(Tm) for Embedded Applications > Omen Technology Inc "The High Reliability Software" > 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >
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