Thanks, Pete. Good tips.
I ordered 10 crystals this morning, ...they are dirt cheap. Will try and test one as you suggested. If it is the 'crystal', a bad crystal, .......what then? Do I try to place one of these cheap ones in the oven, ...or do I try to just run it outside the oven or find a high-temperature crystal??? The crystal oven/controller seems fine, ...hot enough to hurt my fingers. Thanks, ...-Don ------------------------------------------ -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Peter Bell Sent: Wednesday, December 21, 2011 5:28 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Efratom FRK - no 10Mhz oscillator Yeah, that was why I suggested just sticking a random 10MHz xtal across the pins on the board (with the existing xtal wiring disconnected) - if the rest of the circuit is good, then the oscillator should start up with no problems - if it doesn't, then suspect a fault somewhere else. I just pulled out the manual, and I would start by lifting the connection on E7, and connecting a 10MHz xtal in series with a 10pF cap between the E7 pin and ground. This will bypass both the xtal and the frequency adjustment circuit. If that doesn't work, then the oscillator circuit is the problem - if it does work, then remove the 10 pF cap and connect the xtal directly between E7 and E8 - if it still works, it's almost certainly a bad xtal. If it worked with the 10 pF cap but not with the E8 connection, then check the control voltage (E9: 0.5V-17V) - if that looks good, then suspect the frequency control circuit. If it's bad, then try hooking it to +5V to verify the oscillator and then troubleshoot the servo board. Regards, Pete On Wed, Dec 21, 2011 at 5:00 AM, Azelio Boriani <[email protected]> wrote: > 10MHz crystals used in OCXO are designed for the temperature of the oven so > it is not possible to find an off-the-shelf suitable crystal. Better find a > crystal coming from an OCXO. > > On Tue, Dec 20, 2011 at 7:10 PM, Peter Bell <[email protected]> wrote: > >> Hi, Don >> >> It's been quite a while since I worked on a FRK, but from what I >> remember the only signals going to that oscillator board are power and >> the control voltage. It might be worth checking the control voltage to >> see if it's at a plausible value (nominal is 5V, spec range is 1V-16V, >> IIRC) - if you have a spare xtal around, just try connecting it to the >> pins on the PCB and see if it starts up. >> >> I'm not aware of the xtals being failure prone - I have seen one FRK >> with a bad one, but having seen the condition of the system it was >> removed from, that was clearly impact damage. >> >> Regards, >> >> Pete >> >> >> On Wed, Dec 21, 2011 at 1:29 AM, Don Lewis <[email protected]> >> wrote: >> > A little help, pls, from the more experienced. This is my first time >> into >> > one of these .I have listened and learned from you' all for some time, >> > though. It can be intimidating in this close-packed FRK. >> > >> > >> > >> > I am trying to bring up an Efratom FRK I have had for a while. >> > >> > >> > >> > The 10 MHz oscillator does not start upon power on. >> > >> > >> > >> > Any ideas where to look? >> > >> > >> > >> > I have done the following: >> > >> > >> > >> > * I have it opened-up and applied 24vDC and the current starts up >> > initially at 1.45 amp and slowly goes down to ~.6- .8 amps. >> > * Since I have no 10 MHz output, .so I looked at the oscillator >> board >> > and nothing out from it. >> > * The 17 volt dc supply-rail is good, and the VCO input signal to >> the >> > varacter control-circuitry is constantly ramping up and down slowly >> between >> > ~1volt and ~15 volts. >> > * All the transistors in the oscillator circuit seem ok with a VOM, >> > ..and when I purposely inject a 10Mhz signal into the collector of the >> > 'oscillator' transistor (Q3), .I do get a clean 10Mhz out of the unit (of >> > course it won't lock), .and I haven't even been into the rest of the >> unit. >> > * I think the crystal is bad, .I took the cover off the crystal >> oven, >> > it 'looks' ok, . and the crystal heater in the oven is heating and >> > regulating. >> > >> > >> > >> > >> > >> > Any ideas? .does the 10 MHz crystal in these have a history of failing? >> > >> > Can I get a replacement crystal for it easily? >> > >> > How can I test this crystal for pass/fail? >> > >> > >> > >> > Thanks, .just my first test of the waters as a fledging time-nut. >> > >> > >> > >> > Don Lewis >> > >> > Austin, TX >> > >> > _______________________________________________ >> > 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.
