Good points. But I have the 4000 series, so thats what gets used. Also have 74LS but then I would need voltage regulators and level conversion...
On Sun, Jan 10, 2010 at 12:19 PM, Bob Camp <[email protected]> wrote: > Hi > > I would be very careful with the reference conversion. > > Your rubidium probably puts out 10 MHz and the counter needs 1 MC .... > > The 4000 series CMOS gates probably have quite a bit more jitter than some > of the more modern parts. Stuff like the 74AC series will beat them on > jitter. > > Bob > > > On Jan 10, 2010, at 11:48 AM, paul swed wrote: > > > Arie > > Still working on the a26 board. It works but I want to improve the 10 mc > in. > > Most likely a schmitt trigger CD 4093 I might guess. The boards very > simple. > > Since I have 10 mc in the shack from a RB standard I simply square it up > and > > send it to a CD4050 buffer IC to the 10 MC systems in the 5248M. Then > take > > the same 10 MC divide with a CD 4018 to get 1 MC feed this to 3 CD4050 > > inverters. I strongly suspect actually one buffer is more then enough in > the > > package just have not had time to try it. > > > > I also found some HP sloppy work. HP no way. But evidently it does > happen. > > There is a 7474 on the A35 board that has open set and reset inputs. Good > > practice is to tie those high. > > These are floating and as I had seen with age they become slightly > erratic. > > Replaced that chip and will tie the spare leads high. > > > > I have indeed isolated my issue to the tunnel diode gate section. Inject > a > > signal just beyond that and the counter counts. Though incorrectly > because > > no gate action. > > > > I have another 5248 thats been working for years and had never been in > it. > > Well I figured I would borrow the A21 card to confirm the issues and > measure > > voltages. Son of a gone someone else had the same section issue and > cleverly > > replaced the tunnel diode with a ecl 10116. I don't see how they are > gating > > that yet. But I do understand how the 10116 works to amplify and clip the > > signal. So I may indeed copy that circuit if I can not recover the gate > > section of A21. > > Regards > > > > On Sun, Jan 10, 2010 at 11:38 AM, paul swed <[email protected]> wrote: > > > >> Arie, > >> > >> > >> On Sun, Jan 10, 2010 at 7:14 AM, arie schellaars < > >> [email protected]> wrote: > >> > >>> > >>> > >>> > >>> > >>> Hi folks, > >>> My 5245L had faulty nixies and my approach was to use Russian > replacements > >>> available from a Canadian outfit. > >>> The "snags" are. > >>> These nixies , though a direct socket fit , have a glass extrusion at > the > >>> back to > >>> "suck out" or let in the neon gas during manufacture. > >>> I drilled the socket ,slow and carefully here, to allow this extrusion > to > >>> fit into the > >>> socket . There is some room to spare for this on the socket and no > >>> disassembly of the readout card is needed. > >>> The second "snag " is that the figure 5 is in fact an inverted (upside > >>> down) fig 2 but > >>> in practice it's not a problem. > >>> BTW never had a problem with any of the "innards" of the counter > boards! > >>> Would be interested in your details of the oscillator board as , like > you, > >>> mine came without the crystal. The oven container was there but empty! > >>> Have since obtained a crystal in its oven but still not happy with the > A26 > >>> board. > >>> performance AND have run out of Germanium transistors as per on that > >>> board. > >>> > >>> Just had a thought. Ever since I purchased my 5245L many years ago, I > have > >>> been on this Time nut treadmill . I guess I should have known better at > the > >>> time !!! > >>> Now with a shack full of HP and Tek gear and the inevitable rubidiums , > >>> GPS thunderbolts and plain old oxco's , time to call "CQ' is at a > premium. > >>> (Hi) > >>> Cheers from OZ > >>> Arie > >>> VK3DBF > >>> > >>> > >>> Been troubleshooting a 5248 M someone grabbed teh oscilator and A26 > board > >>> from it. > >>> The a26 board was replced with 2 cmos chips and 1 transistor. > >>> Now I am at the counter gate. Darned if I don't have an issue in the > >>> dreaded > >>> tunnel diodes area. Such a lucky day for me. > >>> Need to cleanup and solder in the pseudo a26 board so I can more easily > >>> work > >>> on the gate. > >>> > >>> > >>> > >>> > >>> > >>> > __________________________________________________________________________________ > >>> See what's on at the movies in your area. Find out now: > >>> http://au.movies.yahoo.com/session-times/ > >>> _______________________________________________ > >>> 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.
